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Latest discoveries in the tissue engineering field: “Cyborg tissue”

Tissue engineering is usually dealing with living cells, artificial materials and strong knowledge of organ/tissue physiology & histology when creating a replacement for the dysfunctional organ. Every organ has more or less complicated structure that is vital for its proper functioning. Designing exact replica is not the most complicated part of the tissue engineering (with modern technology and wide anatomical knowledge we have today). The biggest problem with artificial organs lays in the fact that scientist are lacking information on its functioning when inserted back to the body. So far there wasn’t non-invasive method to monitor the cellular behavior and adjustment after tissue transplantation.

However, as with every other medical field, one that is dealing with artificial tissue and organ development is constantly improving. “Cyborg tissue” is latest discovery in this area, where living cells are incorporated into specific nano-wires designed 3D network. Research team from the Boston Children's Hospital and Harvard and Massachusetts University joined together to created a 3D nanoscale scaffold where cells are planted and integrated in one functional system.

Until now, interaction between cells or their individual activity was measured using electrodes, but this method is aggressive and result in cell injury. Main goal of this study was to create a tissue where electronic part will be merged will living part of the tissue, enabling scientist to follow all changes without damaging the cells or disrupting their biological activity. Every biochemical process in the organism is a result of the well organized and controlled cascade of chemical and electronic impulses that are traveling from one part of the body to another, from one cell to a sometimes very distant one. Autonomic nervous system is responsible for maintaining homeostasis in the organism. It is keeping all this processes under control by coordinating complicated cellular signals and cascade events. When artificial tissue is inserted in the body, it can’t recognize the signals body is emitting and as a result it never becomes truly “accepted” and functional part of the body. “Perfect” artificial tissue would be able to mimic intrinsic feedback loops in the body and establish control in the tissue functioning by recognizing and adapting to the chemical signals send by other cells in the body, such as hormones, neurotransmitters or respond to the changes in the pH, oxygen level…. Other important thing scientist had in mind was to a create tissue whose cellular activity would be easily monitored and/or stimulated.

Previous attempts to create bio-engineered sensing networks combining electronics with living cells were focused on 2D models, where cell were growing on the top of the electronic component. Since specific tissue architecture is one of the most important things for normal functioning, creating 3D model is what finally brought success. Newly designed model has a structure like a cotton candy, where silicon wires with ~80 nm in diameter are forming mesh like network or can be shaped like flat planes. Organic polymer is placed around nanoscale wires. Miniature electrodes are connecting wire elements in the mesh allowing nanowire transistors to detect cellular activity without inflicting damage. Pores of this reticular model are big enough and cells could grow freely once they are seeded in this 3D mesh.

Using the heart and nervous tissue cells, artificial tissues with embedded nanoscale networks were created without disrupting cellular structure and functioning. Scientists are able for the first time to track all electronic signals generated by the cells using nano-scale networks. They could also monitor changes in the cellular communication after applying cardio- or neurostimulating drugs.

Besides cardiac and neural tissue, artificial blood vessel with embedded nanoscale networks is created as well. Goal was to design a tissue that could be able to recognize changes in the pH both in- and outside the vessel. Those changes are happening during ischemia and inflammation and early recognition of the potential danger and instant reaction is sometimes essential for the survival.

Application of the newly designed 3D synthetic biomaterial is wide. Scientists could stimulate and monitor cellular interaction without affecting their viability. Pharmaceutical industry could benefit from this model as well; 3D tissue could give a better insight into drug reaction and cellular response than conventional two layer cell culture.