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by Ishani7 at 10-05-2012, 12:26 AM
Mango, Mangifera indica; is one of the world’s most important fruits and admired for its delicious taste and high nutritional value. Mango originated in the Indo-Burma region and has been cultivated for at least 4000 years in the Indian subcontinent. In Sri Lanka, mango has been grown in many parts of the country as a home garden tree in every house. Present extent of mango cultivation has about 12160 Ha. Predominantly, it’s grown in Kurunegala, Anuradhapura, Hambanthota, Puttalam, Monaragala, Jaffna etc.

Mango belongs to the family Anacardiaceae. Mango cultivars in Sri Lanka include Ambalavi, Malvana, Karathacolomban, Rata, Willard. Alampur Baneshan, Alphonso, Bombay, Brahm Kai Meu, Keitt are some mango varieties cultivated around the world.

Anthracnose caused by Colletotrichum sp. is a major pre/post-harvest disease which seriously constrains the production, marketing and export of mango and may be of a quarantine concern. Colletotrichum gleosporoides was considered the major pathogen causing anthracnose and to a lesser extent Colletotrichum acutatum.

Fruit spoilage caused by anthracnose ranges from a slight loss in the quality resulting in reduced sales to total spoilage of the fruits. Anthracnose fungus can infect almost all aerial parts of the mango tree causing blossom blight, leaf spot/blight and fruit rot.

Inoculation takes place at the initial stages of fruit development. The observable external symptom often only becomes apparent after ripening, by which it is usually equated with the edibility of the fruit. As the fruits ripen, symptoms appear as one or more dark spreading lesions. Decay is initially fairly superficial with some lesions becoming sunken in ripened fruits. Moisture extradition may occur and pink coloured spore masses can develop in the centre of the lesions. Uncolonized flesh is comparatively free of off-odours or tainting. Anthracnose stem end lesions can be confused with stem end rot lesions. Small dark lesions can also develop on young fruits particularly in wet conditions, around insect damage or when factors favour fruitlet shedding. On maturation of the fruit before harvest, tear stain pattern infections, consisting of numerous small limited lesions can develop with symptoms radiating from around the stem end or at contact points between fruit or leaves and fruit. Tear stain lesions often remain discrete as fruit ripens.

Disease susceptibility varies for different mango cultivars. Cultivars such as Willard, Ambalavi are more susceptible when compared with cultivars like Karathacolomban which is considered to be resistant for anthracnose. Antimicrobials present in the fruit peel are a major factor influencing the disease development and disease susceptibility. As the fruits ripen, the antimicrobial content in the fruit peels decrease facilitating the disease development.

Control of anthracnose disease requires periodic spraying with the fungicides in orchards and efficient post-harvest treatment. The degree of disease spread varies depending on the susceptibility of the host plant and environmental conditions. Fungicides used include benzimidazole, chloronitrile etc.

Identification of the pathogen to species level is important in disease management. Traditional methods of identification were based on morphological characteristics including shape and size of spores, appresoria formation, growth rate and sensitivity of benzaimidazole fungicides. Colletotrichum gleosporoides and Colletotrichum acutatum are defined as species complexes comprising of many species. Colletotrichum gleosporoides complex includes C. asianum, C. cordylinicola, C. fructicola, C. gloeosporioides, C. horii, C. kahawae subsp. kahawae, C. musae, C. nupharicola, C. psidii, C. siamense, C. theobromicola, C. tropicale. Colletotrichum acutatum complex comprises of C. simmondsii, C. fioriniae (formerly C. acutatum f. sp. fioriniae), C. lupine etc.


Earlier it was considered that conidia produced by Colletotrichum gleosporoides are cylindrical with rounded ends & conidia produced by Colletotrichum acutatum are fusiform. Growth rate of Colletotrichum gleosporoides was considered to be higher when compared with Colletotrichum acutatum. Colletotrichum acutatum was found to be relatively resistant to Benzaimidazole compared with Colletotrichum gleosporoides. These methods are not accurate enough to identify the pathogen. Colletotrichum sp. has more complex genetic and morphological characteristics which does not directly correspond to the species. Molecular methods can be used to identify the Colletotrichum sp. accurately. Species specific primers have been developed for amplification of DNA of these two species; Cg Int primers for Colletotrichum gleosporoides and Ca Int primers for Colletotrichum acutatum. With combining traditional methods with molecular methods, wide understanding about this pathogen can be obtained which can be used in disease management.
by Ishani7 at 10-04-2012, 11:28 PM
In molecular biology procedures, DNA extraction is a preliminary method. Methods for DNA extracting differ from plants to animals to bacteria. Even among bacteria there are different procedures involving DNA extraction. These variations are mostly due to the differences in their structure. For an instance, fungi have a thick wall consisting of chitin which is difficult to degrade. DNA extraction procedure should be monitored carefully as it is temperature sensitive and pH sensitive. It is essential to store extracted DNA samples at -20C. All the equipment used for DNA extraction should be sterilized. For microbial DNA extraction, it is important to use pure cultures. At the same time, using fresh samples is of significant importance.

In any method of DNA extraction, the wall or the membrane of the cell is broken using a detergent. After cellular constituents some out, nuclear membrane is lysed if present. The impurities like proteins and cell debris are removed by centrifugation. Isopropanol is added to precipitate proteins. Naked DNA is generally stored in a buffer solution at a temperature below freezing point. It is essential to prevent extracted DNA from degradation. If DNases are present in the stored extract, genetic material would be lysed.

In digestion of cell wall, content of lysis solution will vary depending on the organism. Plant cell walls contain cellulose. If high amount of cutin is present on plant material, digestion will be different from normal procedure. Extraction of DNA from plant materials usually involves crushing of plant material in liquid nitrogen. Chitin is the major constituent of fungal cell walls which makes it very tedious procedure. Enzymatic digestion is quite effective in lysing cell walls in case of microbes. Since it is costly various other chemical and physical methods are used. Chemicals used include detergents such as EDTA or SDS. These detergents can be ionic or non-ionic. The lysis solution usually contains a buffer to maintain pH and a salt. Physical methods include high temperature treatments, microwave treatments, high pressure applications, sonication etc. However both chemical and physical methods can lead to destruction of the genetic material. In case of DNA extraction from bacteria, lysis of the cell wall greatly depends upon whether the bacteria are gram negative or gram positive.
Apart from these, extracting DNA from different human cells such as red blood cells has specific procedures. If the specimen is pure, the purification is much easier. If it is associated with more contaminants, additional purification procedures may be necessary. For an instant, for microbial cultures its important the sample to be free of agar as it can inhibit Polymerase chain reaction, which is the next step in case of many molecular biology procedures.

After the cell wall is degraded, the nucleus will be exposed in case of eukaryotic organisms. Next the nucleus membrane will be lysed using a detergent. Nuclear lysis solution won’t have to be a strong one. In many organisms, plasma membrane structure is basically the same.
RNA content is important in DNA extraction. RNA can be removed by using RNase enzyme which shows its optimum activity at 370 C. RNA content is different in organisms. In case of Yeast and plants it’s generally high. Depending on this, the concentration of RNase can be increased to minimize RNA content in the final extract.
For protein removal, generally an ammonium salt is used which precipitates proteins with other cell debris. Protein removal is important as DNA of some organisms is associated with high content of proteins. This protein removal also removes the enzyme system of the cells. This is a crucial as enzymes such as DNase can lead to degradation of genetic material. A mixture of phenol and chloroform is used for protein purification in traditional methods.

After digestion of cell wall and membranes and digestion of protein and RNA, the retained cell debris can be removed by centrifugation. The speed of centrifugation for this is usually 10000 g. After centrifugation, the cell debris will make a precipitate at the bottom and the supernatant will contain DNA. When isopropanol is added to supernatant, DNA forms a thread like strand associated with air bubbles. Then the sample will be centrifuged to a higher speed to precipitate DNA followed by ethanol wash.

For storing DNA, Millipore water or TE buffer can be used. This should be neutral and free from contamination.
by Kamat2010 at 10-04-2012, 03:14 PM
In the therapeutic use of any bioactive molecule, the consideration of its bioavailability within the body is very essential. In the discovery and design of prospective, viable Drug Candidates (DCs) also, the knowledge of its molecular structure and properties are essential, which indirectly determines its oral bioavailability. The polymorphic nature of the drug metabolizing enzymes within the body causes variation in the oral bioavailability as well as the clearance of the DCs. Hence, the comparison of the oral bioavailability data of the actual drugs and the DCs helps in correlating their physical properties, which is very essential part in the drug discovery process.

Bioavailability of a drug candidate may be defined as the extent to which its active part is absorbed or released from the actual ingested molecule and is available at the site of action. From the pharmacokinetic point of view, the oral bioavailability plays a very important role in the screening of the prospective DCs as it determines the effective dose, which is essential for the proper drug action within the body. Bioavailability determines the form in which the DC must be administered within the body such that it has optimal effect within the body. The DCs can be administered in the form of tablets, coated tablets, capsules, powder, solution, suspensions, formulations with controlled release, etc. Depending on the site of action of the DCs, the form of the drug product to be administered can be determined.

The formation of the active moiety of the DC, its rate of the dissolution into the fluids present at its action site, the permeability of the DCs through the membrane of the tract into the systemic circulation are important factors that determine the bioavailability of the DCs. The inherent physical properties of the DCs such as their crystalline structure, particle size, etc also determine their bioavailability. Some physiological properties of the patients also determine the bioavailability of the DCs such as the age, sex, weight, medical history, metabolism, etc. The co-administration of different drugs also has a pronounced effect on the bioavailability of the drugs and the DCs. The type of food and type of diet of an individual determines the bioavailability of a drug or a drug candidate within his body. Although, these studies may give an idea of the bioavailability but various other factors like stress, hormone levels, exercise, the change in the inherent body fluids due to some reason, the presence of other diseases, etc may affect the bioavailability of the drugs or DCs drastically. Hence, before the administration of a drug or DC, thorough knowledge about the history of the patient is essential.

The bioavailability of a drug or a DC is known by measuring its concentration in the blood or urine. The bioavailability determination is carried out using different methods such as in-vivo studies, blood- level study, urinary excretion study, etc. In the in-vivo studies, blood or plasma sample is collected at various time intervals, which correlates with the bioavailability but the data is reliable only if a large population size is used for the study, which is not practical always. The pharmacologic effect quantification is also a method of measuring the bioavailability, whereby the response produced on the body using a particular dose of drug or DC is measured. However, this method is also difficult as the pharmacologic effect cannot be quantified in all cases. Hence, alternative methods like the blood-level tests, urinary excretion studies are used, which use a small sample size of population and are feasible. The type of dosage i.e. single and multiple dosage studies are essential for bioavailability determination. It is to be seen whether a drug or DC requires a single dose or multiple doses at regular time intervals to reach the optimum level in blood or plasma to produce the desired action. In-vitro studies have also been carried out whereby the dissolution of the drug or DC has been measured. Nevertheless, the in-vitro studies are carried out in controlled conditions, which do not correlate with the actual conditions within the body.

The Bioequivalence studies have also proved very essential while carrying out the bioavailability studies. Some DCs are the new formulations of existing drugs. These are considered fit for administration by FDA (Food and Drug Association) , when the bioavailability of the formulations of the drugs i.e. their concentration in plasma to time profiles do not have much statistical difference. Hence, the bioequivalent may be defined as the bioavailability of more than one formulation of the drugs. Thus, bioavailability studies form the backbone of drug development and discovery studies.
by Ishani7 at 10-04-2012, 02:58 AM
Genetics is the mystery behind many non-communicable diseases today. In some cases, it is possible to analyze this using family history of genetic disorders. But this is not practical when a disease is caused by mutations. When there’s a risk for a certain disease genetically, it is better to control other factors influencing the disease. Prenatal diagnosis is used to diagnose genetic diseases at pregnancy.

Diabetes mellitus is a non-communicable disease which is widely found throughout the world. It is a multifactorial inherited disease. Environmental factors play a major role in the expression of these genes. Diabetes is classified into two types; type I which is insulin dependent Diabetes and type II which is non-insulin dependent. Onset of insulin dependent diabetes is at early childhood and type II diabetes is seen at 30-40 years.

Diabetes mellitus I is caused by autoimmune destruction of islet β cells in pancreas. This destruction of islet β cells causes insulin deficiency and deregulation of anabolism and catabolism. More than 13 different susceptible gene loci have been identified. This locus behaves as a haplotype. Later it was discovered that β polypeptide of DQ II protein which is a dimer is a part of HLA. This protein has aspartic acid in 57th position in protective or neutral alleles, If it’s replaced with a neutral amino acid like serine, alanine; they are susceptible for DM type I. Amino acid in the 57th position is important for the specificity of antigen binding. Another cause of DM type I is variable number of tandem repeats (VNTR) in the promoter region of insulin encoding gene. If VNTR’s increase, these individuals are more susceptible to type I Diabetes. Patients with DM type I has a reduced tolerance for glucose level, hyperglycemia and ketoacidosis. Type II Diabetes is the most common which is characterized by relative insulin deficiency and resistance. Hyperglycemia and hyperinsulinemia are symptoms of Diabetes type II. Persistent hyperglycemia desensitize the islet β cells such that less insulin is released for a given glucose level. Elevated basal insulin levels down regulate the insulin receptors thereby increase in insulin resistance. Glucagon is unopposed and it’s secretion increases worsening hyperglycemia. An allele at short tandem repeat variations in the intron for a transcription factor TCF7L2 is associated with type II Diabetes. It encodes a transcription factor involved in the expression of hormone glucagon which raises blood glucose concentrations.

Rheumatoid arthritis is an autoimmune disease that causes chronic inflammation of joints and also can cause inflammation of the tissues around the joints. It is a systemic illness that can last for years. It causes joint destruction and functional disability. It is commonly seen in women. Lymphocytes are activated and chemical messengers like cytokines are expressed in inflammated areas producing symptoms like swelling, stiffness of joints, tendons etc.

X linked agammaglobulinemia is a genetic disorder. This is also called as X linked hypagammaglobulinemia, Brufon syndrome. It is more commonly seen among males. Individuals with this genetic defect do not produce mature B cells, which are responsible for the production of antibodies. People with untreated XLA are prone to develop serious and even fatal infections. XLA is caused due to a mutation in X chromosome of a single gene known as Bruton’s tyrosine kinase (Btk) gene. This mutation leads to a severe block in B cell development and a reduced peripheral Ig G immunoglobulin antibody production in the serum. Btk gene is responsible for mediating B cell development and maturation, through a signaling effect on B cell receptor. It is primarily an immune deficiency disorder.

Sickle cell anemia is an autosomal recessive disorder. It is caused due to a point mutation in β polypeptide gene. Diseased people are homozygous for the sickle cell allele. Heterozygotes for sickle cell allele who are healthy but carriers; are called as sickle cell trait whereas homozygous diseased are called as sickle cell anemics. Red blood cells of diseased individuals have a characteristic property of undergoing reversible alterations in shape when subjected to changes in the partial pressure of Oxygen. RBC’s become sickle shaped instead of flat discs. In the point mutation which is a substitution of the gene encoding for β polypeptide, the 6th amino acid, Glutamic acid is substituted with Valine.

Apart from these diseases; Phenylketonuria, graft versus host disease, Neurofibromatosis, Polycystic kidney disease are among genetic factorial diseases. Environmental factors such as age, nutrition, other diseases also affect for these diseases.
by Ishani7 at 10-04-2012, 12:29 AM
During organ transplantation, blood group as well as tissue type is considered. Tissue type refers to a group of proteins on the cell surface with antigenic properties of a person. As the compositions of these proteins are decided by a large number of alleles, these are almost unique to a person. These proteins are called as human leukocyte antigen (HLA) system or MHC proteins. MHC is major histocompatibility complex, composed of large cluster of genes located on the short arm of chromosome 6. As it indicates, this is important for the compatibility of tissues during transplantations. On the basis of structural and functional differences, these genes are classified in to three classes, two of which class I and class II genes correspond to human leukocyte antigen (HLA) genes which play an important role in regulating genetic response in tissue transplantation between unrelated individuals. MHC molecules play a major role in antigen presentation during immune response.

HLA class one and class two genes encode the cell surface proteins that play a critical role in the initiation of immune response and specifically in the presentation of antigens to lymphocytes, which cannot recognize and respond to an antigen unless it complexes with a HLA molecule on the surface of an antigen presenting cell. Many hundreds of different alleles of HLA class one and class two genes are known.

The class one genes; HLA-A, HLA-B, HLA-C encode proteins that are integral parts of plasma membrane of all nucleated cells. A class I protein consists of two polypeptide subunits. Peptides derived from intracellular proteins are generated by proteolytic degradation by a large multifunctional protease; the peptides are then transported to the cell surface and held in a cleft formed in the class one molecule to display the peptide antigen to cytotoxic T cells. Class I molecule is made up of two polypeptide subunits; a variable heavy chain encoded within MHC and nonpolymorphic polypeptide, β2 microglobulin that is encoded by a gene outside MHC, in chromosome 15.

Class II region composed of several loci such as HLA-DP, HLA-DQ, HLA-DR that encode integral membrane cell surface proteins. Each class two molecule is a heterodimer, composed of alpha and beta subunits which are encoded by MHC. Class II molecules present peptides derived from extracellular proteins that had been taken up into lysosomes and processed into peptides for presentation to T cells.

According to the traditional system of HLA nomenclature, the different alleles were distinguished from one another serologically. An individual’s HLA type was determined by seeing how a panel of different antisera or reactive lymphocytes reacted to his or her cells. These antisera and cells were obtained from hundreds of multiparous women who developed immune reactivity against paternal type I and type II antigens expressed by their fetus during the course of their pregnancies. If cells from two unrelated individuals show the same pattern of reaction in a typing panel of antibodies and cells, they are considered to be of the same HLA type and the allele represented would be given a no such as B27 class I HLA B.
When MHC class I and class II genes were identified and sequenced, a single HLA allele initially defined serologically were shown to consist of a multiple alleles defined by different DNA sequence variants even within the same serological allele. Most of the DNA sequence variants change a triplet codon and therefore amino acid in the peptide is encoded by that allele. These alleles are codominant. Each parent has halotypes and expresses both.

Most of the autoimmune conditions that are associated with abnormal immune response directed against one or more antigens thought to be related to variation in the immune response resulting from polymorphism in immune response gene. In some cases, it’s due to a particular MHC allele being present at a very high frequency on chromosomes that also has a disease causing mutation in another MHC gene. Perhaps different polymorphic alleles result in structural variations in these cell surface molecules leading to differences in the capacity of proteins to interact with antigen and T cell receptor in the initiation of an immune response and affects critical processes as immunity against infections and self-tolerance to prevent autoimmunity.

Some HLA alleles are found commonly while others are rarely or never seen. It results from a situation referred as linkage equilibrium which is a complex interaction of many factors such as low rates of meiotic recombination, in small physical distance between HLA loci, environmental influences and historical factors Because acceptance of transplanted tissues largely correlates with degree of similarity between donor and recipient HLA halotypes, the donor for bone marrow or organ transplantation should be ABO compatible and HLA identical sibling of the recipient. The differences in the distribution and frequency of all the alleles and halotypes within the MHC are the result of complex genetic, environmental and historical factors play in each of the different populations.
by Ishani7 at 10-03-2012, 11:48 PM
Pharmacogenetics can be defined as the study of genetic response related to drug response. Pharmacogenetics is a combination of Pharmacogenomics: the study of entire genome related to drug response, Pharmacokinetics: drug metabolism and Pharmacodynamics: interaction between drugs and their molecular targets. This is crucial where genetics come to control medicines. In general people say, a certain medicine would not work for one person, while another person can get healed from that for the same disease. Medical Practitioners ask the patient before prescribing medicine about drugs that may cause adverse reactions in their body which may be an antibiotic or any other kind of drug. These adverse reactions caused by drugs in certain people are most of the time genetically inherited. Therefore it is important to take a look at family history, when taking medicine as some responses may be fatal.

During the study of drug metabolism, it’s important to pay attention on absorption of drugs from gut, distribution, drug cell interactions, breakdown of drugs in liver and excretion.

Isoniazid is a drug used for the treatment of tuberculosis. After this drug is absorbed from gut, the level of the drug in blood is initially high and reduces slowly in healthy people. Due to genetic errors, the inactivation of the drug can be slow or rapid in some people. In rapid inactivators, the level of drug decreases rapidly in the blood. In contrast, the level of the drug remains high for some time in slow inactivators. Slow inactivators of this drug are homogenous for autosomal recessive allele which encodes liver enzyme N-acetyl transferase. High levels of isoniazid in blood can be harmful as it causes some side effects such as liver damage. Slow inactivators have a greater risk for this.

Succinyl Choline is a drug that is used for relaxation of muscles that was introduced in 1950’s. It is used in the induction phase of anesthesia which is metabolized by plasma enzyme cholinesterase. In sensitive patients, destruction is slower and resulted in respiratory arrest with the intake of the drug. Succinyl choline sensitivity is inherited as an autosomal recessive trait which is caused by mutations of CHE 1 gene. Sensitive patients can now be identified by a blood test that monitors cholinesterase activity.

Primaquinone is a drug used in treatment for Malaria. Some people were found to be sensitive to this drug. The sensitive people can take the drug for few days without any side effects, but starts to pass very dark/black urine. Jaundice, reduction in red blood cell count and Hemoglobin are symptoms produced by these sensitive people in response to the drug. This occurs due to a deficiency of the enzyme, Glucose 6-phosphate dehydrogenase which is a X linked recessive trait found commonly among Mediterraneans. Patients with the deficiency of this enzyme are also sensitive to drugs such as Phenacetin, Nitrofurantan, Sulfonamides. These drugs should be carefully used for treatments of these patients.

Coumarin(Warfarin) is an anticoagulant which is used in treatments for many diseases to prevent blood clotting. This drug is metabolized by cytochrome P450 encoded by the gene CYP2C9. Isoenzyme 2C9 is the functional enzyme in metabolizing the drug. VKORC1 is another gene important for degradation of this drug. This gene is involved in the production of target enzyme for warfarin action and it converts Vitamin K into an active form which activates Vitamin K dependent clotting factors.
Debrisoquine is used in the treatment of hypertension and it’s a derivative of guanidine. Many Europeans are poor metabolizers of this drug. This metabolic defects are due to an allele which is homozygous for autosomal recessive gene; CYP2D6 in P450 gene in chromosome 22. A mutation in this gene results in poor metabolism. This gene is involved in metabolism of many drugs.

Leukemia is also known as blood cancer. Thiopurines are used to suppress immune response in autoimmune conditions in patients with transplanted organs. This drug has serious side effects including severe liver damage. Poor metabolism of this drug is due to variations in thiopurine methyl transferase activity which is involved in methylation of thiopurines. This variability caused by genetic differences between people is one of the best examples for the importance of Pharmacogenetics in medicine.
by Ishani7 at 10-03-2012, 11:38 PM
When we cut apples or bananas, they turn brown in colour with time. This makes it unpleasant to eat. During roasting coffee beans, they turn brown which enhances its quality. Starchy or sugary food becomes brown and has a bitter taste. All these brown pigments produced are due to specific reactions taking place during food processing. There are negative impacts as well as positive impacts are observable. Food constituent present and processing conditions are equally important for these interactions. These include Enzymatic browning, Mailard browning and Caramelization.

Phenolic compounds; monopheols and diphenols present in fruits and vegetables act as the substrate to enzymatic browning. These phenolic compounds are important as antioxidants and the degradation of these results in loss of nutritional quality. Enzymatic browning occurs mostly during handling and preparation of food items and during long term storage. In the reaction phenolic compounds are converted into melanin pigments. Enzymatic browning can take place at refrigeration temperatures. Enzymatic browning is catalyzed by a group of enzymes called oxidoreductases which includes polyphenol oxidase, phenolase, tyrosinase and catecholase. Oxygen acts as the Hydrogen acceptor in the reaction. End product, melanin can bind with proteins which can be a problem in digestion. Enzymatic browning spoils the quality of dehydrated products, blanched products etc. Prevention can be done by inactivation of the enzyme system of the fruit or vegetable, decreasing oxygen concentration by dipping in water or using lime or salt.

Melanodin pigments are one of the major products of Maillard Browning which includes pyrazines, imidazoles, reductonoses, and hydroxymethyl furfurals. Maillard browning is also known as non-oxidative browning. These pigments are reddish brown in colour and insoluble in water at room temperature. Other products include volatile food flavours and aroma compounds, UV absorbing compounds. Aldehydes, Ketones and amines serve as the starting material for Maillard browning. pH and the amino acid composition matter a lot in this reaction. The structure of the end products depends on whether the substrate is an aldose or a ketose. These compounds undergo different arrangements (Amadori and Heyns) in the formation of the final product which can be further degraded via aldol condensation and polymerization. Nutritive value of foods is lost when amino sugars are formed. Essential amino acids are lost and lysine is the most susceptible. For Maillard browning to take place favourable pH should be above the isoelectric point of constituent amino acids. Usually in the range of pH 7.8-9.2, the reaction proceeds vigorously. In strongly acidic food, Maillard browning does not take place to a significant extent. Intermediate moisture levels are more suitable for this reaction. Metal ions increase the rate of these reactions. And pentoses, monosaccharides and aldoses are known to react faster than hexoses, disaccharides and ketoses respectively. Maillard browning can be controlled by reducing the moisture content, removal of substrates, limited use of heating steps and using chemicals such as Potassium metabisulfite (KMS) or Sodium metabisulfite (SMS). It is found that some products of Maillard browning are mutagenic. Some degradation products formed before Melanoidin pigment formation may contribute to nitrosoamine formation. Melanoidin production is a significant issue in case of roasting of cereals as it leads to loss of essential amino acids.

Stecker degradation is another process where essential amino acids are destroyed during heat processing and long term storage. Reactants include α-dicarbonyl compounds and amino acids. If Maillard browning has taken place in food, it is assumed that stecker degradation has occurred. This reaction does not contribute to colour, but important for flavour and aroma. Products from this type of browning include aldehydes, pyrazines, and sugar fragmentation products. Favourable conditions for this type of browning are almost similar to Maillard browning.

Caramelization occurs during direct heating of carbohydrates which results in thermolysis of sugars. Temperature is crucial for this process. In Caramelization, wide range of flavour compounds and brown pigments are formed. This process involves number of reactions resulting in anomeric shifts, ring size alterations, breakage of glycosidic bonds, dehydration etc. Products have conjugated double bonds which can absorb colour and are polymers which are not dissolved in water. Caramel pigments are commercially available and are used in products like coca cola, puddings etc. Rate of Caramelization is increased with high temperatures and high pH.
by Kamat2010 at 10-03-2012, 10:20 PM
Cancer has always been a very intriguing subject of research as no permanent cure has been developed for it yet. Different factors responsible for causing cancer like the presence of many genes, proteins, etc in the tumor cells have been identified but still no vaccine or medicine has been discovered for curing cancer completely and permanently due to the rapid rate of proliferation of the tumor cells and their unpredictable nature of localization and differentiation. Moreover, the different treatments as chemotherapy, radiation, etc seem to affect the nearby normal cells drastically as the targeting of tumor cells specifically is very difficult. Every day a new research regarding it is developed and a new factor responsible for cancer development is found, making the research study on cancer a never-ending subject.

The Cell Cycle is studied to a great extent during cancer research. DNA undergoes replication and in this process, the end replication problem, which causes loss of important sequences of genes present at the ends of the DNA. Thousands of tandem repeats of hexa-nucleotide sequence TTAGGG are present in the repetitive non-coding DNA along with proteins. They are known as telomeres. The cell phenotype of the cells is controlled by the presence of telomeres, though the exact relationship between them is quite complex. The telomeres play an important role in tumorigenesis, cell cycle regulation, genomic stability, etc. The telomeres are present in the ends of the chromosomes and help in the recognition of the actual ends of linear double-stranded DNA from the breaks within the double-stranded DNA. The telomere undergoes shortening with each cycle of replication and the ultimate Cell senescence or growth arrest is determined by the maximum number of replication cycles undergone by the DNA to reach the optimal length of the telomeres. Actually, the telomeres possess a cap like structure made of different proteins and these proteins are responsible for DNA strand repair and regulation of telomere length.

The tumor suppressor proteins p53 and Rb are present within the cell and are known as downstream effectors. They regulate cell proliferation, as they are responsible for the senescence or permanent arrest in growth of the cell, which is imposed on the cell once the telomeric DNA reaches the optimum length. The telomere shortening process triggers the activation of the pathways involving the production of the p53 and Rb proteins, thereby activating the process of cell senescence. The suppression of the genes encoding these proteins resulted in the development of immortal cells, due to suppression of cell senescence.

Some cells bypass senescence or cell growth arrest by the inactivation of the signalling pathways of p53 and Rb. These cells undergo cell division until the telomere length is shortened critically. This causes the end-to-end fusion of the DNA and the trigger of DNA- strand break repair mechanisms. Hence, these cells devise mechanisms, in which they maintain the telomere length by alternative pathways (ALT). In this pathway, the telomerase, which is a reverse transcriptase enzyme, plays an important role in using associated RNA to increase the length of the telomeric ends, which has been demonstrated by the cloning of the hTERT (human Telomerase Reverse Transcriptase) encoding gene. The role of telomerase in cellular immortality was shown in different cells like retinal pigment epithelial cells, fibroblasts, endothelial cells, etc.

The normal cells undergo a number of mutations, which result in a number of transformations. These transformations give rise to a number of changes in the cellular functions and properties like the uncontrolled division of cells resulting in the immortality of the cells and thus formation of tumor cells. Apart from the suppression of cell senescence, the loss of integrity of the telomeres is also an important factor resulting in the formation and development of tumor cells. The uncontrolled division of cells result in very short telomeres that ultimately cause fusion in the ends of DNA resulting in genomic instability and thus the transformation of cells. The telomere length is maintained in 90% of transformed, tumor cells by the expression of the hTERT gene. Hence, it is seen that the telomeres and their related proteins play a very important role in tumorigenesis, leading ultimately to cancer and that telomeric integrity and homeostasis are very vital for the maintenance of genomic stability within the cell.
by priyasaravanan_1406 at 10-03-2012, 07:04 PM
Proteins are called as the “building blocks of body” which has significant role in all cellular functions contributing to the overall function of the body. Proteins are the key structures in all biochemical and metabolic pathways of a human body. The dominance of proteins in cell functions is highly commendable, which lead to the development of various fields like proteomics and protein biotechnology enabling the complete understanding and study of proteins under one roof.

The basic units of the proteins are called as amino acids. One or more amino acids linked by peptide bond contribute to the structure of protein. The amino acid sequence is specific for each protein and the sequence of amino acids is controlled by gene sequence. There are twenty different amino acids and they are Glycine, Alanine, Leucine, Isoleucine, histidine, methionine, phenylalanine, cysteine, glutamine, glutamic acid, asparagines, aspartic acid, proline, serine, threonine, tryptophan, tyrosine, valine, arginine and lysine. The various combination of these amino acids result in a specific type of protein. Thus any alteration or absence of even a single amino acid in an amino acid sequence results in protein dysfunction.

Proteins are classified based on their structure, function and composition. Proteins are grouped under primary, secondary, tertiary and quaternary types based on their structure. The factors like solubility and shape classifies proteins as fibrous, globular and intermediate proteins. Some examples of fibrous proteins are elastin, collagen and keratin which are insoluble in water. Globulin and insulin are globular proteins, soluble in water. Intermediate proteins depict the nature of fibrous proteins in shape and solubility like globular proteins. Fibrinogen is a classic example of an intermediate protein.

Based on the protein composition, they are grouped into simple and conjugated proteins. The simple proteins are the ones which are made up of only amino acids whereas the conjugated proteins represent the presence of proteins along with other molecules. The albumins, globulins, histones and scleroproteins are simple proteins. The lipoproteins, glycoprotein, nucleoprotein, chromoprotein phosphoprotein, flavoprotein and metaloprotein are all conjugated proteins. Based on their function proteins are grouped under categories like enzyme, storage, transport, hormonal, receptor, contractile, defensive and genetic proteins.

Most of the proteins are synthesized in the human body by transcription of DNA into mRNA (messenger RNA) and translation of mRNA into amino acids (proteins) with the help of tRNA (transfer RNA). Some proteins are derived from the dietary supplements like meat, egg, milk, vegetables, pulses and nuts. The deficiency or dysfunction of the bodily synthesized protein and deficiency of dietary protein causes various diseases.

Since all the synthesis and sequence of amino acids are controlled by genes, any mutation in the gene causes either dysfunction of the protein or absence of the protein. As a result various diseases and syndromes develop. Marfan Syndrome (dysfunction of fibrillin protein due to mutation of FBN1 gene), Huntington disease (dysfunction of huntingtin protein resulting in excess glutamine), Hereditary hemochromatosis associated with the HFE protein, Alzheimer’s disease are some of the diseases identified as a result of protein dysfunction due to gene abnormality or mutation. Transmissable spongiform encephalopathies like mad cow disease, Creutzfeld Jakob disease (prion disease), cancer, cystic fibrosis are diseases due to misfolding of proteins or absence of correctly folded proteins. Phenylketonuria is a condition in children whose ability to degrade the amino acid phenylalanine is disturbed.

Kwashiorkor, Marasmus and Marasmic- Kwashiorkor (grouped under Protein-Energy malnutrition) diseases are the mainly discussed dietary protein deficiency related disorders. To combat these disorders, required quantity of protein intake through diet is suggested based on the severity of the disease. Also excess intake of protein poses problems like ketosis, kidney and liver related disorder and so on. The other diseases like hypertension, diabetes which imposes stress on kidney resulting in kidney failure is associated with a condition called proteinuria where the essential proteins passes through kidney and appears in urine.

The protein related disorders due to dietary intake is well managed. If the disease is due to malnutrition of protein, then the patient is given protein rich diet or if it is due to excess intake of protein then the patient is restricted of protein intake. Whereas the treatment of genetic related protein disorders or syndromes is quite challenging and the subject of gene therapy should be understood and considered for treatments.
by BojanaL at 10-03-2012, 06:19 PM
In vitro fertilization developed over 30 years ago and is one of the most popular conceiving methods with couples having infertility issues. It’s conception under controlled laboratory conditions. Cells are placed in Petri dish, sperm fuse with egg and after conception is confirmed – fertilized egg is inserted into woman’s womb. Other method is intracytoplasmic sperm injection where sperm cell is injected directly into the egg. By now, around 5 millions babies are born after conceived using in vitro technique. Out if 100% babies born each year, 0.3% are test tube babies.

Pre-implantation genetic diagnostic or embryo screening is used to confirm the genetic “health” of the embryo. If genetic disorder is detected, egg will not be implanted and abortion will be avoided. This kind of tests could be performed on oocyte as well. When oocyte and sperm are used for screening, methods are known as oocyte and sperm selection. Pre-implantation screening can prevent: Duchenne muscular dystrophy, cystic fibrosis, fragile X syndrome, sickle cell disease, Charcot-Marie-Tooth disease, hemophilia A, Huntington's disease, just to name it few. When couple is at high risk of developing offspring with serious genetic disease(s), embryo screening combined with in vitro fertilization offer a solution by selecting healthy embryo that will be implanted afterwards.

There is couple of ethical issues associated with embryo screening and pre-selection. Human leukocyte antigen (HLA) matching is used to detect embryo that will match sick sibling and be able to donate umbilical cord blood stem cell for Fanconi anaemia, b-thalassemia or leukemia treatment. In other words, parents are making baby (by selecting right embryo) so they could use it for the treatment of their already born sick child. Sex related genetic disorders could be prevented (such as fragile X), but this kind of testing could be used by future parents also to decide which gender they prefer better. Some people having minor genetic disorder (like deafness) could select embryo that will develop same illness instead healthy one, because they want to share same characteristic with their offspring.

Pre-implantation tests are not 100% correct and accurate. When results of testing are done, overall conclusion is made by analyzing person’s medical history, family history and just finished genetic test. Mutations that are altering DNA are associated with numerous illnesses, but variations in DNA are happening naturally as well. Genetic polymorphism is not associated with any kind of disease but could make embryo screening inconclusive and difficult to interpret. Sometimes it’s hard to tell if genetic alteration is positive sign indicating future illness or simple polymorphism that wouldn’t affect health at all.

Usually, 2 days (6-8 cells stage) or 5 days old embryos (blastocyst stage) are inserted into the womb. Medium, where embryo is grown before implanting, contains glucose, vitamins, amino acid, cholesterol…all nutrients necessary for successful development. Depending on the woman’s age, health and the quality of the available embryos, usually 1 or 2 embryos are inserted. Some countries are approving implantation of up to 6 embryos which greatly increase the chance of pregnancy but also increase chances of multiple pregnancies.

Assisted zona hatching is used to help implantation process. Drilling the layer around egg will help egg hatch out once in uterus and ensure endometrial nesting. Hormone supplements (known as luteal support) are part of the treatment because progesterone, progestins and GnRH agonists can increase the chance of successful implantation and embryogenesis. After two weeks, if happened – pregnancy will be easily detected by blood or urine test. Today, 30% of in vitro fertilizations are finalized successful with healthy babies born at the end.

Cryopreservation is method used to preserve oocytes or embryos for the future in vitro fertilization cycles. Extracted oocytes or successfully fertilized eggs can be preserved by lowering the temperature below zero. Cryopreservation is useful when medical issues and treatments can decrease future success in pregnancy (chemotherapy is affecting ovaries and number of remaining oocytes). Couple that is going through in vitro fertilization can cryopreserve “leftover” embryos to be used in the next round in case first attempt doesn’t end up successfully. Cryopreservation is also used when eggs or embryos are planned for donation. Oldest successfully fertilized egg was stored for 16 years.

In vitro fertilization enables not just infertile couples, but single parents or gay couples to become parents. It is not cheap, simple and 100% successful method, but still raises the chance of pregnancy greatly comparing to other methods.
by nihila at 10-03-2012, 04:32 PM
Visual impairment and blindness are the major health problems presently. The most common reason for eye disorders is age-related retinal degeneration. As there is lack of effective treatment for degenerative retinal diseases, stem cell-based therapy can provide a promising approach in restoring and sustaining retinal function and prevent blindness, thus holding great hope for many people. Stem cell therapy holds great promise for the treatment of retinal diseases. The source of stem cells for a particular therapy is a major issue. Not all stem cell types can be induced to differentiate into cell types needed for treatment. It is encouraging that a number of different sources and types of stem cells and precursor cells have been identified from which relevant cell types for ocular stem cell therapy can be derived. These include fetal stem cells, cells from brain, limbus, conjunctiva, corneal endothelium, and retina.

Researchers have identified, stem cells of central nervous system in a single layer called the retinal pigment epithelium, or RPE, which lies behind the retina and which may provide a way to repair the damage from age-related macular degeneration, or AMD, the leading cause of vision loss in people over 60. Researchers say, cell types generated from the stem cells can be used for testing drugs for AMD and other eye diseases, but the ultimate goal would be to regenerate eye tissue destroyed by AMD so sight could be restored. Tests have suggested that the cells are stable and do not appear to cause tumors, a potential danger inherent in some types of stem cells. More studies are needed to determine whether the cells can restore lost vision or not.

An American Retinal Surgeon has treated 7 patients with a new technique for administrating adult stem cells for eye disease. Adult Stem Cells are stem cells are typically obtained from the bone marrow of the patients itself, where there is a high concentration of specific types of stem cells found to be useful for many diseases. At times they are obtained from the blood directly. The patients range from 2 years to 87 years and suffered from a variety of eye diseases including AMD or Age Related Macular Degeneration, Myopic Macular Degeneration, Bulls Eye Retinopathy- a type of hereditary retinal disease, Retinitis Pigmentosa, and Optic Nerve Disease. Previously the stem cells were injected behind the eye to treat ophthalmic problems but the exact location and how far they might be from the targeted retinal or optic nerve tissue was not always known but now with the new technique the stem cells can be placed precisely adjacent to the eye in a very safe manner.

Embryonic stem cell therapy used to treat degenerative form of blindness has showed no signs of any adverse effects. Embryonic stem cells are extraordinarily versatile cells that are found in early-stages of embryos that can differentiate into any tissue of the body. Scientists have been trying using them as a replacement for tissue lost through disease or lost in accidents or war. Advanced Cell Technology (ACT) Inc. has conducted experiments to treat eye diseases using embryonic stem cells. Around 50,000 embryonic stem cells that diversified into replacement cells for the pigmented layer of the retina were transplanted into two blind volunteers one with dry age-related macular degeneration, the leading cause of blindness in the developed world, the other who had Stargardt's macular dystrophy, the commonest form of vision loss among young people. For six weeks, the patients received treatment to prevent their immune systems from attacking the implanted cells. In the first four months, no signs of cancer, rejection or other safety concerns emerged and both patients recovered a little vision.

Although results achieved on applying stem cell technology to treat eye disease has a shown good results more work is required. The main issues that require focus are identification of the optimal precursor cell types, establishment of growth and differentiation conditions that meet safety and effectiveness standards, and the manipulating surrounding environment to allow transplanted cells to survive and function. Transplanted neuronal precursors can connect into the inner plexiform layer and optic nerve head. But directing their axons to appropriate targets is yet to be explained. A substantial progress in this aspect and other areas is needed to be achieved.
by Kamat2010 at 10-03-2012, 03:49 PM
What is so special about the use of stem cell in research?

Research in Stem cells is a fast growing area in the field of Biotechnology. The potential of the stem cells to provide treatment for many untreatable diseases is one of the most important factors which is leading to a great deal of study and development in this topic. The departments in many colleges, hospitals, etc. due to the vast potential of stem cell research are pursuing the basic and translational areas of research on the stem cells. Many programmes of study are being developed on various aspects of stem cell research, some of which include the embryonic stem cell lines generation of human; isolation and clonal expansion of the adult progenitor cells of bone marrow; embryonic stem cell line development; stem cell preservation using banana lectins; cardiac stem cell development, characterization and differentiation of pancreatic, liver, and mesenchymal stem cells; ocular surface disorders treatment using limbal cells; hematopoietic stem cells transplantation, etc.

Stem cell is an immature cell that can develop and specialize into almost any cell throughout the body. This potential of the stem cell is the reason for the extensive research regarding it.

They are of two types:

a) Adult stem cells, which are found in already specialized tissue of brain, muscle, skin, bone, and blood. They mainly replace the dead or damaged cells acting as a repair system. Owing to complex growing and differentiating conditions, laboratory studies using them are difficult,

b) Embryonic stem cells, which are developed from a newly fertilized egg and are capable of developing into any cell throughout the body. They are much easier to handle due to favourable conditions for growth. The other type of stem cells that has been identified in recent times is the stem cells derived from the umbilical cord and placenta that can develop into various types of blood cells. The embryonic stem cells can have different sources.

The stem cells are developed by In-vitro fertilization (IVF) technique forming a blastocyst and using it for various researches on genetically inherited diseases or by nuclear transfer, whereby the nucleus of a fully formed egg is removed and replaced by that of an already differentiated adult cell. The development of embryonic stem cells have ethical issues as they are formed by taking the blastocyst of a mother undergoing IVF treatment, hence proper consent is very crucial. The stem cells are also categorized into different classes according to their differentiation and development plasticity as: Totipotent cells, which can develop into a fully developed and functional organism; Pluripotent cells, which can develop into any type of tissue in the body but cannot develop into a complete organism; and Multipotent cells, which can develop into a specific and limited number of tissues.

Some of the basic properties of the stem cells have provided for successful research. The stem cells can be cultured into a cell line easily. The differentiation and development process of the cells can be studied easily with the use of the stem cells. The stem cells can survive for long period thus can be used in drug discovery process for testing of various drugs as well as for toxicity studies. The role of various genes on the development process of human and also the cause and effect of various mutations on the genes can be studied. The stem cells can be used to make rat or mouse chimeras whereby the stem cells of human are implanted on the rat or mouse to study the effect of various drugs, diseases, etc.

Stem cell research is very crucial in the development of treatments for various diseases. Possibilities in the treatment of Parkinson’s disease, cancer, Type-I diabetes, etc are being looked at as these diseases are related to the cell differentiation and development process. The stem cells have been successfully used in the treatment of blood diseases and skin diseases. In case of blood tissue, the hematopoietic stem cells are available that can regenerate any type of blood cells and in case of skin graft, the stem cells of the skin are present just below the top layer of skin and can be used successfully to regenerate the skin after burns, etc. The successful regeneration of blood and skin tissues has provided hope for possible treatments with the stem cells in future.
by BojanaL at 10-03-2012, 04:26 AM
Forensic science entered our lives couple years ago when CSI television series start showing. I admit, they caught my attention instantly and I became addicted to the latest mysteries in front of Gil’s or Horatio’s team of experts. Most people I know are fascinated by high tech laboratories and sophisticated evidence collecting techniques that could be seen in every episode. If you put familiar faces from the show aside, forensic can be defined as application of diverse scientific methods and knowledge to solve legal issues (crimes or civil actions). Disciplines such as paleontology, chemistry, biology, botany, osteology, odontology…are widely used during crime investigation.

Forensic biology is what fascinates me the most. Every crime scene is associated with more or less biological materials. Blood, urine, semen, saliva, hair, skin….those are true markers of the crime. They can be analyzed in various ways and used for different purposes.

Hair can be analyzed using the polarized light microscope; it can be source of DNA (hair follicle) or can link suspect or some third person with crime scene. Species specific differences in hair structure can be easily recognized once hair is under the microscope. Also, hair can be used for drug screening as some substances could be found in hair 90 days after consumption.

Blood is probably the most common bodily fluid seen at the crime scene. To be sure that its blood we are looking at, small amount of Luminol is usually splashed. It reacts with blood by bonding with iron from hemoglobin. Positive result (indicating presence of blood) will be obvious by blue glow in darkened environment. Bloodstain pattern analysis is also very helpful during the investigation. Blood is usually main source of both victim’s and suspect’s DNA. To exclude animal derived blood, test with human antigen is applied. Once you confirm human origin, blood type and DNA analysis could be performed. DNA profiling is technique used to identify person. It’s like finger printing – each person has its unique DNA. Although people share 99.9% of the same genetic material, differences in DNA pattern are still big enough to distinguish one person from another. Variable number tandem repeats (VNTRs) analysis is used for that purpose. VNTR are groups of two of more nucleotides that are repeating continuously on different chromosomes. Their length is variable. VNTR analysis provides evidence of genetic similarity between samples because “variants” are completely different between unrelated individuals and highly similar between close relatives. Toxicological analysis is used to detect presence of drug that could be responsible for any kind of poisoning. Gas chromatograph-mass spectrometer is most often used method for separation (if the mixture of chemicals is present), differentiation and quantification of the substances in the blood sample.

Urine can be easily detected on the cloths or some part of the furniture because it becomes fluorescent under UV lights. It is mostly used for toxicology screening as all chemicals are metabolized and excreted eventually by urine. Urine drug test kits are used for quick and efficient detection of certain chemicals in field (in situ) or in laboratory. Here’s the list of drugs that could be easily detected (with 99% accuracy) in just a couple of minutes using some of the marketed drug kits: marijuana, cocaine, opiates (like heroin), methamphetamine, ecstasy, amphetamine, phencyclidine, tricyclic antidepressants, barbiturates, benzodiazepines, methadone, oxycodone.

Alpha amylase is enzyme present in saliva at high doses and thus widely used as indicator of hidden saliva at the crime scene. Saliva can be collected easily and it’s highly accurate in detecting illegal substances in traces (that can be found in saliva while circulating the body). Saliva is popular and often used DNA source. Epithelial cells from the inner lining of the mouth are “equipped” with the same genetic material (both in quality and quantity) as DNA from the rest of the body.

Semen on the crime scene is mostly associated with sexual assaults. It is highly fluorescent and can be detected with UV lamp. Lab method used to confirm presence of sperm is best known as Christmas tree stain (because of the bright colors seen under microscope). DNA from the sperm is used for DNA fingerprinting and suspect identification.

Beside described biological material, teeth and bones are used for personal identification and age and gender determination.

Forensic science is combining most interesting methods from various scientific disciplines. If you have quick mind, cold blood and enough will to get necessary knowledge you can become next forensic expert. Maybe it’s not the cleanest and easiest jobs to do, but at least it’s humane.
by priyasaravanan_1406 at 10-01-2012, 08:28 PM
This article explains importance of stem cells, procedure of collecting them and how they are stored in a stem cell bank.

The Stem cell's ability to repair, renew and regenerate is the basis for all the researches in the field of stem cell therapy. This unique characteristic of stem cell is very attractive and the research and findings in this field prove to create a revolution in medicine. In recent times, the knowledge on stem cells, its features, availability and its significance in treating diseases created awareness among people enabling them to adopt stem cell collection and preservation techniques.

The collection of stem cells depends on the source from where the cells are harvested. Based on its source stem cells are classified as embryonic stem cell, fetal stem cell, umbilical cord stem cell and adult stem cell. Stem cells are utilized for treating diseases by altering its characteristics of undifferentiated to well differentiated specific cell type under controlled condition.

The cells resulting from the division of the zygote are called the embryonic stem cells because of its totipotency to develop into all kinds of specific cell type. The embryonic stem cells are harvested from the embryos in vitro by adopting a technique called in vitro fertilization. In vitro fertilization is a method used widely in treating infertile couples. In this method the sperm is inserted into the egg under controlled conditions in a laboratory environment. The use of in vitro embryos for harvesting stem cells is a very strict procedure which is done only by obtaining formal consent from the couple whose egg cell and sperm cell are used in developing the embryo. The embryonic stem cells, once harvested are subjected to cell culture technique. In this technique, the research fellow or the scientist decides the specific media and other environmental and physiological factors for the cells to grow into well defined, specific cell type. The advantages of using embryonic stem cells in a research is that they are fresh cells, not interrupted by any physical, chemical or environmental condition and mostly devoid of any chromosomal abnormality. The main restriction in using embryonic stem cells for treating a disease is its uncontrolled cell division which may cause cancer.

The umbilical cord blood is a rich source of stem cells. The umbilical cord is the connection between the mother and the baby through which nutrients are supplemented from the placenta to the baby in the womb. At the time of delivery, baby is separated from the mother by cutting the umbilical cord. In the event of collecting the cord blood for stem cells, the cord between the placenta and the baby is clamped and an efficiently trained person draws the blood from the umbilical cord by inserting a needle. The collected blood is transferred from the needle to the sample vial and sent for storage. Sterile conditions are maintained during this procedure of collection to avoid any contamination of the sample. People with a family history of known genetic diseases or other metabolic diseases can preserve their baby’s cord blood which can be used effectively in future treatment of various diseases. The collected blood can be stored as such or the stem cells can be harvested by separating procedures and stored. The family members, the baby itself and siblings are highly benefited by storing umbilical cord stem cells.

Adult stem cells are the existing cells in various tissues in adult body. The cells in bone marrow, muscle tissue, skin cell and nerve cell are some of the source for adult stem cell. The collection of stem cells from bone marrow equips a surgical procedure in which the subject from whom the stem cells are extracted is anesthetized first. Then a needle is inserted into the bone marrow at a selected site to draw the stem cells. Bone marrow transplantation is a widely used treatment method in treating various disorders. Collection of adult stem cells from blood is done by drawing blood intravenously from one hand and passing it through a processor which separates the stem cells from the blood. Once the stem cells are separated the blood is allowed to re-enter the body intravenously through the other hand. The restrictions to adult stem cells are any present chromosomal abnormality, or damage to the cells due to various physiological and environmental condition. In comparison to the embryonic stem cells, the division of adult stem cells can be controlled to an extent and hence the risk of acquiring cancer while treating for a disease is minimized to an extent.

Apart from these discussed stem cell types extensive research have lead to the discovery of stem cells in amniotic fluid and menstrual blood. Deriving stem cells from the amniotic fluid, rules out the ethics in using embryos for stem cell extraction. Also the stem cells from menstrual blood and its application in treating arthritis, cardiac disease has been proved in a research.

Though the collection procedure differs depending on the site from where the cells are extracted, the storage method is common(also called banking). The collected samples are cryopreserved using liquid nitrogen. There are many emerged and emerging stem cell banks rendering services to the people by collecting and preserving the stem cells. The key in resolving various disorders lies in the preserved stem cell in a stem cell bank.
by Kamat2010 at 10-01-2012, 07:53 PM
Ubiquitin is an essential protein present abundantly within the body and is used for the normal functioning and degradation of other proteins within the cell by covalent modification. The ubiquitin acts along with the Proteasome complex, which is multicatalytic proteinase. The Ubiquitin-Proteasome complex plays a very important role in the turnover of the different cellular proteins, which are usually degraded or damaged in nature, by the Ubiquitin-Protease pathway (UPP). The UPP has no effect in general on other normal proteins and the proteins, which are to be degraded, are targeted by the protease system by conjugation with ubiquitin.

The Ubiquitin-Protease system is responsible for the regulation of the mitosis and other important steps in the regulation of the cell cycle by the degradation of the damaged and unnecessary proteins, thereby preventing the accumulation of the unnecessary proteins within the cell. Thus, ubiquitin-protease system plays an important role in the maintenance of cellular homeostasis within the body by regulating the different signalling pathways, antigen-rocognition, etc. The accumulated damaged proteins within the cell cause apoptosis i.e. programmed cell death. This apoptosis is prevented by the Ubiquitin-protease system. Hence, the study of this system was undertaken to see if the inhibition of this system has any effect in promoting apoptosis of tumor cells thereby helping in cancer therapy. This could target either inhibition of the ubiquitination of the proteins to be degraded or the inhibition of the proteasomes, both of which cause protein degradation inhibition resulting ultimately in apoptosis.

The large sub-cellular organelle, which is multi-subunit protein complex, is the site for the ATP-dependent Ubiquitin mediated protein degradation within the cell and is known as Proteasome. The Proteasome is also known as 26S proteasome and consists of two subunits: 20S subunit, which is the catalytic subunit and the 19S subunit, which is the regulatory subunit. The 19S subunit consists of ATPases, which hydrolyse ATP thereby causing change in the conformation of the 20S subunit that binds to the unfolded substrate. The isopeptidase in the 19S subunit causes the cleavage of the ubiquitin molecules, which are then available for the ubiquitination of the subsequent proteins ready for degradation. Many research studies have proved that many inhibitors are available for the inhibition of the proteasome complexes, which ultimately lead to apoptosis. Some studies have proved the effectiveness of proteasome inhibition on the treatment of the multiple myeloma. Unlike other cells, multiple myeloma is susceptible to the accumulation of the unwanted proteins like large number of immunoglobulin chains as they are derived from the antibody producing cells. Due to this accumulation, the inhibition of the proteasome with the use of inhibitors causes the programmed cell death or apoptosis of the multiple myeloma cells. The normal cells are not affected in this case with the use of the proteasome inhibitors as the normal cells do not accumulate unwanted proteins in large quantities due to less need for proteasomal action. Moreover, the normal cells have alternative methods of removal of the damaged proteins like autophagy, whereby the unnecessary, aggregated proteins are transported to the lysosomes for removal, which helps in the removal of these proteins. Thus, it can be seen that this method of autophagy prevents apoptosis in some tumor cells. Hence, the use of inhibitors of autophagy along with the proteasome inhibitors may help in the apoptosis of the tumor cells better.

In some cases like breast cancer therapy, indirect function of the ubiquitin-protease system is seen. It is seen that the use of certain compounds was found to increase the ubiquitin mediated degradation of proteins required for normal cell function thereby causing apoptosis. The use of camptothecins was found to increase the proteolytic degradation of the topoisomerases by the ubiquin-mediated mechanisms. In some other cases, the oestrogen receptors were degraded by the UPP in the postmenopausal patients suffering from breast cancer with the use of certain drugs.

In this way, it can be seen that the UPP plays an important role in the different areas of cancer therapy. Extensive research is going on in this field and the exact mechanism by which the inhibition or the overfunctioning of the protease system plays a role in the programmed cell death of the tumor or cancer cells is yet to be analysed.
by BojanaL at 10-01-2012, 06:55 PM
Green technology (known also as clean or environmental friendly technology) consider using latest technological achievements to produce different systems, products or equipment that could help preserve natural environment. Development of renewable energy sources, recycling and agro-technological improvements are some of the examples of green tech.

We are all wasting energy. If you are sitting in front of the computer – it’s using battery or is plugged directly to electricity source. Chair you are sitting on, bottle you are drinking water from, mouse you are using to navigate the web, internet router near the table, flowerpot on the window…it’s all made by burning hundred billions of petroleum annually.

Fossil fuels are widely used for vehicle fuel production and to power the industries and machines, but they are required for development of everyday consumer products as well. Everything from contact lenses and dishes to diapers, toys, tires and chemicals is made out of fossil fuels. However, fossil fuels are non-renewable sources of energy and we will run out of oil reserves eventually. Besides being non-renewable, burning the fossil fuels increase atmospheric CO2 level and enhance green house effect, thus contributing to the global warning phenomena. Global warming accelerates polar ice melting and subsequent climate changes that are affecting all living creatures on Earth. Is there anything we can do to help save our planet and its resources before it’s too late?

For the beginning, alternative energy sources could help keep our environment healthy while energy is produced. Sources are everywhere around us, we just need to find the way to exploit them.

Wind turbines are designed to collect energy of the wind and convert it into electricity. Principle is simple: airflow rotates the propellers, they are moving magnets and magnet movement produces electricity. Wind farms can be seen all around Europe, Asia and USA and all together 83 countries in the world are relaying completely on this kind of energy for commercial use. In 2011, 50% of total energy produced in Germany and Spain was derived from wind and sun energy. Wind power is the most cost effective alternative source of energy today.

Solar energy can be used in a couple of ways. Solar thermal collectors (that can be seen on the rooftops of many European houses) are absorbing sun light and use it further for residential heating. Photovoltaic systems are absorbing sun energy and convert it into electric energy. Just 16% of absorbed solar energy can be transformed into electricity which makes solar energy less efficient than one derived from the wind.

Hydroelectricity is term describing electricity produced by the power of the water. Gravitational force of falling water is generating electricity. Hydroelectric plants are not expensive and this is one of the most used alternative energy source (150 countries all over the world are using energy produced by hydropower).

Geothermal energy is derived from geothermal sources like geysers, magma, hot springs. It’s used for electricity production or for direct heating. Geothermal plants that are collecting heat from earth's core and drilling procedure are expensive, which makes geothermal energy less popular compared to other renewable sources.

Biomass can be described as any kind of plants, agricultural waste or vegetation (dead or alive) that could be used as energy source. Energy could be released by thermal conversion or by transforming biomass into biofuels and biogases. Depending on the sources of biomass used, it can be more or less cost effective. Main issue with biomass derived energy is inevitable pollution of both air and water.

Nuclear power is produced in nuclear power plants. Electricity is generated by controlled nuclear fission (nuclear chain reaction). Since fission creates radioactivity, nuclear reactor is equipped with protective shield. However, couple of dramatic events (such as Chernobyl and Fukushima) associated with nuclear leakage are noted in the history and consequences of those events are still present.

Every alternative source of energy has its pros and cons. If they are effective in energy production that doesn’t necessarily mean that they will be eco friendly. Also if they are harmless to the environment there’s a chance that manufacture process will be expensive. While searching the best possible solution for the next renewable energy source we need to keep world sustainable. As long as we are wisely using natural resources (taking what is needed without disturbing natural balance) – we are on the right track.
by BojanaL at 10-01-2012, 05:22 AM
Technology in Color Red!

Red biotechnology is dedicated to the medical field improvements. It uses living organisms while designing novel therapeutics. Antibiotics are the best example, but vaccine and genetic engineering are also typical examples of red technology.

Antibiotic is any compound or substance that is killing or slowing down growth of microbial cells. Penicillin, discovered by Alexander Fleming, is first and probably best known antibiotic. New era in therapeutic research began once superior effect of Penicillin was recognized. Today, market is flooded with antibiotics and most people use them on a regular basis for treatment of different infections. Antibiotics can be divided in a couple of categories. Bacteria killing ones are known as bactericidal while those that disturb bacterial replication without killing the cells are known as bacteriostatic. Both groups are targeting different part of the bacterial cell and have different mechanism of action. Bactericidal antibiotic will affect synthesis of the cell wall or cell membrane, while bacteriostatic will disrupt enzymes necessary for the cell replication. Antibiotics have narrow or wide spectrum of action. Those with narrow spectrum will be effective either with Gram positive of with Gram negative bacteria, while those with wide spectrum could successfully combat both Gram positive and Gram negative bacterial infections. Mass production and uncontrolled use of antibiotic led to resistant bacteria development. Every year spectrum of bacteria that are becoming resistant to the marketed antibiotics is getting wider. Mutation that enables bacteria to survive high doses of antibiotic is passing to the next generation via mitosis or by horizontal gene transfer (if newly created gene is on the plasmid). That way bacterium could become resistant to more than one antibiotic. If a bacterium is carrying more than one resistance gene it's called superbug. Alternatives to antibiotic therapies include viruses that could infect bacteria (phage therapy), bacteriocins (engineered peptide with narrow spectrum of action), chelation technique (where micro nutrients necessary for bacterial growth are restricted), vaccines that are modulating immune response, biotherapy (using protozoa feeding on infectious agents), probiotics (that will compete with pathogens)....

Idea of developing resistance to disease by learning immune system to recognize and instantly fight the illness came from Edward Jenner in 18th century. Arm-to-arm inoculation (taking a sample from infected skin and inoculating it into healthy person's skin) was the first attempt to vaccinate the human and protect him against smallpox. It was successful technique but vaccination wasn't medically recognized and popular until Luis Pasteur created a rabies vaccine in 19th century. That's when vaccination became routine procedure. I was immunized with vaccines against diphtheria, measles, tetanus, tumps, pertussis, pubella and polio during my childhood. Now, list is expanded and all people born after 2000th year are getting seven more (Hib, Hepatitis B, Varicella, Hepatitis A, Pneumococcal, Influenza, Rotavirus). Vaccines are made out of the dead or attenuated virus, or just proteins and toxins that are inducing illness. If some parts of the virus are poorly immunogenic – then conjugates are made (viral particles attached to large proteins stimulate immune response). Vaccines could be mono or polyvalent, protecting against one or more agents, respectively.

I couldn’t finish the story of immune system and associated therapeutics without mentioning latest innovations in that field. Understanding of immune system and its complex molecular cascade led to monoclonal antibody (MAb) therapy development. Using the antigen of choice, monoclonal antibody is easily created. It could be used for treatment of all kind of illnesses (from arthritis to cancer). 13% of all deaths in the world are cancer related. There are over 200 different types of tumor that could be detected in human population. Beside chemotherapy and surgical procedures, MAb therapy is one of the solutions. There are couple of ways MAb could defeat the cancer. Radioimmunotherapy (using murine derived antibodies) is effective when applied to radioactive sensitive tumors such as lymphoma. Antibodies are tailored to target cancer cellular antigens specifically (without radiating the rest of the body). Antibody-directed enzyme prodrug therapy (ADEPT) is still under investigation (with promising results). ADEPT combine cancer targeted antibody with drug activating enzyme that will convert non-toxic agent into toxic (after drug ingestion) and act directly on cancer cells. Immunoliposomes are combinations of antibodies and liposomes. Liposomes could be a drug or therapeutic nucleotide carriers. Idea is to deliver tumor suppressing genes into tumor or to destroy tumor directly with attached drug. This method is still under investigation.

Field of medicine changed drastically in the recent couple of decades. Just like we found a way to defeat the bacterial and viral diseases, we’ll find the way to solve current medical issues. Cancer will be “smallpox” one day; it’s just a matter of time.
by Ishani7 at 10-01-2012, 03:26 AM
Plant pests range from nematodes to birds and mammals. Most pests of crops important for humans are insects belonging to Lepidoptera, Diptera, Coleoptera etc. Genetic manipulation has for and against points in recent research which requires further studies on development of invasive plants, genetically improved pests etc.

Bt approach is one example where genetic manipulation is used for pest resistance. Genes encoding for the cry proteins with pesticide activity of Bacillus thuringiensis bacterium is incorporated into plant genomes as in cotton. Bt genes in plant genome produces cry proteins and develop a self-defense mechanism against pests. Bt genes produce number of toxins which affect insect larvae. These cry proteins are also known as Insecticidal crystal proteins (ICP) which is an endotoxin produced by bacteria during sporulation. Genes encoding for ICP’s are carried on bacterial plasmids which is a superfamily of related genes. Cry proteins are different in size to one another, but still share a common active core. Active core of Cry A gene has 3 domains; which were specialized for creating pores through membrane of the insect gut, receptor recognition and for protection from degradation in the protein product. When the cry proteins are ingested by insect larvae, the protein crystals are solubilized in mid gut. Larger cry proteins are proteolytically cleaved to release the active fragment of protein. This interacts with high affinity receptors in the mid gut brush border membrane. This binding results in opening of cation selective pores in the membrane. The flow of the cations into the cells results in osmotic lysis of mid gut epithelial cells. Conditions prevailing in mid gut of larvae result in activation of specific cry proteins. Among cry proteins, δ endotoxins are extremely toxic at low concentrations. Isolated crystal proteins in mass scale are used as biopesticides. Appearance of resistant pests, altered interactions between plants and environment are widely discussed issues on Bt crops. It was found that pollen grains of Bt maize were toxic to Monarch butterfly, which may interfere with environmental interactions.

Genetic control of pests through reciprocal translocation is another advanced method. Reciprocal translocation leads to reduction in fertility, population displacement and genetic transformation with a conditional lethal trait. This involves reducing or nullifying the fertility of pest species using genetic changes.

In reciprocal translocation, broken pieces of two non-homologous chromosomes swap. If the break occurs without damaging a critical area of the genome, the organism will have the full complement of original gamete information and can appear perfectly normal. It is the production of gametes where the genetic abnormality manifests itself. When normal diploid cells undergo meiosis, homologous pairs of chromosomes line up with each other during Metaphase 1. But when there is a reciprocal translocation, the homologous pairs of the original chromosomes line up with one another making a peculiar pattern at Metaphase 1. Normally during Anaphase 1, homologous chromosomes migrate to opposite poles, pulled by spindle apparatus. But with a reciprocal translocation, there are there are three possible ways for the chromosomes to sort themselves to migrate to opposite poles. This reduction division can produce six different gametes. Theoretically, fertility of the translocation heterozygote would be reduced to one third of the normal. This can occur naturally and spontaneously, but frequency can be increased by low doses of ionizing radiation. To make necessary genetic changes; radiation is used. It is evident that not all insect species can tolerate the radiation levels necessary to make them sterile. Practically, probabilities of possible pairings of chromosomes are not equal. So fertility is 1/3 to 1/2 of normal. If more than one translocation occurs, fertility would be reduced more. The possible crosses between viable gametes of translocation heterozygote would produce a normal diploid, a translocation heterozygote and a translocation homozygote (1:2:1). The impact of reduced fertility of the translocation heterozygote on the overall population will depend on the species involved and its environment. Multiple translocations are used to create a strain that is genetically identical to wild type except that the order of genes on chromosomes scrambled. The wild type and the translocated strain are equally viable and fertile. But the hybrid is viable but not fertile. This is used in the phenomenon of population displacement.

Inherited sterility is an approach to the genetic manipulation of pest population in which released insects are fertile, but their progeny will be infertile. This is known as delayed sterility. Cytoplasmic incompatibility and multiple polyploidy also can be used to introduce genetic alterations to produce infertility.
by BojanaL at 09-30-2012, 09:24 PM
Technology in Color Blue!

Blue biotechnology is combination of aquatic and marine organisms with technology to get new sources of energy, develop new drugs, extract new active ingredients (that could serve many purposes) or just to increase seafood production and its safety.

Sea is covering ¾ of the planet. Life began in the ocean and diversity of sea creatures is enormous (~230 000 species). Even though we explored a huge portion of the ocean, a lot of species, life cycles and other mysteries are waiting to be discovered.

Algae are probably not the first thing that comes to your mind when you think of the sea, but they are certainly one of the commonest ocean inhabitants. They are close relatives of terrestrial plants, and just like them, algae act like “ocean lungs” by providing oxygen during photosynthesis. They vary in shape and size: from multicellular microscopic creatures to over 60 meters long monsters. Algae are very large and diverse group of organisms and they are classified in a couple of clusters according to the type of chlorophylls and other pigments they have. Some algae fossils are old 1.5 -1.6 billion years.

Why algae are so important? They provide oxygen, serve as food or even shelter for other marine animals and can be a partner for a lifetime when in symbiotic relationship with coral reefs or sponges… Roles they play in marine ecosystem are easily disturbed by human factor. Overfishing and pollution of the water results in algal overproduction and inflict severe damages to the whole aquatic ecosystem. There’s a simple explanation: fish are eating algae and keeping them under control while waste derived nitrates and phosphates act like fertilizers and accelerate algal production. Without fish, they are growing unstoppably and catastrophe is inevitable. An algal bloom is taught battle to win and so far only solution is control of pollution of the ocean and prevention of excess fishing.

Algae are exploited in so many ways.

They can serve as food (particularly in Asia). Salad made of ulva is easy way to ensure you daily doses of fibers and vitamins.

Agar- agar is a polysaccharide derived from red algae. It gets gelatinous after boiling and it’s used as a substrate for microbial cultivation. Agar is also used in food industry as thickening agent, as ingredient in various deserts, or can serve as appetite suppressant and laxative… Beside agar, carrageenan is other polysaccharide extracted from red algae that is also widely used in food and pharmaceutical industry.

Algal pigments are very important for their photosynthetic activity but can serve as natural coloring agents once extracted.

Industrial pollution increases demand for environmental friendly solutions. Algae find their role in biodegradable plastic production.

High rate of agriculture increases a need for efficient fertilizers. Since algae are natural source of essential plant nutrients – they serve as perfect fertilizers. And best thing is that you can collect them on your own!

For me, the most important thing about algae is that they could be used as a biofuel. Fossil fuels are formed during the anaerobic degradation of the organisms died long time ago. Over 85% of energy in the world is provided by fossil fuels. The reserves of fossil fuels are limited and they are not renewable. If this tempo remains unchanged, reserves will be depleted soon. That’s why so many efforts are made in finding and establishing new and renewable energy sources. Algal fuel is good alternative. It could also reduce the amount of CO2 released during the fuel burning process by absorbing certain amount of the gas during the growing phase (CO2 is essential for photosynthesis). Algal fuel is much cheaper than conventional fuel and it can be produced easily (waste water as substrate is also an option). It’s biodegradable and wouldn’t affect environment. Manufacturing process is simple. Lipids extracted out of the biomass are turned into biodiesel and bioethanol and biobutanol are end products of carbohydrate fermentation. Besides liquid fuels, methane and biogasoline can be derived as well. In any case biomass “leftovers” are used as an animal feedstock.

Algae are growing rapidly and produce huge amount of biomass in short time. They could be exploited in numerous ways. If we start acting smart and responsible, high production will be obvious in biofuel factories instead in the ocean and success in future renewable energy will be guaranteed.
by nihila at 09-30-2012, 06:23 PM
Carbon Nanotubes (CNTs) are allotropes of carbon. They are cylindrical tubes made with a diameter ranging in nanometers. They are made up of graphene sheets (carbon atoms) rolled like a cylinder. These graphene sheets can be rolled in different ways and the angle of rolling gives different CNTs different properties. CNTs with a single cylindrical carbon layer is known as single walled carbon nanotubes (SWCNTs) which have a diameter of 0.4 – 2 nm and those containing multi layers is known as multi walled carbon nanotubes (MWCNTs) with inner tubes pertaining to a diameter of 1 -3 nm and outer tubes to 2- 100nm. They belong to fullerene family. They can be open at both side or can contain cap at one end

CNTs are the most dynamic and most promising nanomaterials for variety of fields. In medicine they can be used for drug delivery, cancer treatment, biosensors, etc. Because of their unique physical, chemical and biological properties they have various therapeutic uses. They are the strongest materials found till now. They sp2 bonds between the carbon atoms make them the strongest materials. They are highly conductive.

CNTs can be designed to function as carrier systems for nanoparticles that are used in and are mentioned as Nano carrier drug delivery systems. With different type of rolling they acquire different properties and their functions vary. Variety of biological molecules or drugs can be attached onto the surface of the CNTs or they can be filled inside them and injected into the body.

The main aspect here is how these CNTs reach the target cells. For this the surface of CNTs with the anti-cancer drug is coated with specific antibody that can identify the target cell and then released into the body. To track the CNTs, they are loaded with quantum dots which generate fluorescence when subjected to certain radiation. The Nano needle shape of these CNTs, the hollow monolithic structure and their ability to bind with different functional groups provide delivery of drugs directly to target tissue preventing harm to normal tissues. CNTs are introduced into the body with a Nano injector.

There are two main routes of CNTs to enter the cell, one is through passive diffusion through lipid bilayer and the other is by endocytosis where the CNT attaches to the external cell membrane and then absorbed by cell using energy dependent process. SWCNTs and MWCNTs have different cell penetration mechanism. SWCNTs internalize into cells, long SWCNTs localize into cytoplasm and short SWCNTs can enter nucleus. MWCNTs cannot enter the cells, they are excluded.

The release of drug into the target tissue is also an important aspect. CNTs loaded with drugs are sealed at both ends with molecules which can be cleaved intracellularly or the drugs can be attached to the walls of CNTs and can be cleaved by various conditions in the cell like acidic environment, pH, etc. They can also be released when subjected to heat.

The combination of CNTs with radiofrequency or radiation can be a potential treatment for cancer that is harmless to normal cells and is highly efficient. When CNTs are exposed to laser heat is generated from these CNTs and it increases the surface temperature of the cells. This causes coagulative necrosis and as a result of this heat shock protein induction is observed in deeper tissues indicating that CNTs can be used to extend the depth of radiation therapy.

Despite the biological advantages of CNTs, there are limitations to their use as medicines because their surfaces of CNTs are highly contaminated with metal catalysts and amorphous carbon, various factors like size of the nanoparticles, their surface chemistry, dosage, morphology and chemical components are also responsible for the magnitude of their toxicity. Several studies have stated that when appropriate molecules are attached to the surface of CNTs they become less toxic and more biocompatible. This attachment of molecules is called functionalization and studies have observed that a high degree of functionalization reduces the toxicity of CNTs.

The unique and dynamic properties of CNTs make them interesting to be multifunctional therapeutic agents in cancer treatment. The major drawback is its toxicity. It is a relief that functionalizing CNTs would allow them to be biocompatible for clinical applications. Despite this, the advances made by CNTs are of great significance in for us.
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