Our aim is to develop novel conductive materials that technologically recapitulate biological systems. Such materials have the potential to revolutionize electrode-tissue-interfaces and allow for seamless long-term integration of bioelectronic devices into biological tissues.
Bioelectronic devices help patients around the world to participate in a normal life by replacing lost body functions. The metal-based electronics used in these devices show a great physicochemical and functional mismatch compared to living matter. Most importantly, these materials function purely electrically, whereas in biological tissue, electronic and biomolecular signals are tightly interconnected. This mismatch leads to massive limitations in the use of modern biomedical devices.
Using conductive hydrogels, we are able to recapitulate the physicochemical properties of living tissue combined with high electrical conductivity in one material system. Hydrogels are hydrated polymers that can be tuned in their mechanical properties to be as soft as the tissues they are interfacing. By combining charged colloidal particles (laponite), a covalent polymer hydrogel (polyacrylamide) and the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT), we are able to synthesize highly conductive, organic and soft interpenetrating polymer networks.
The negative charges of the laponite particles embedded in the polyacrylamide matrix act as a dopant for the conductive polymer. This leads to a massively increased conductivity compared to undoped hydrogels. In addition, the electrostatic interaction of the particles strengthens the polymer network and makes it highly elastic. This makes the materials stable over multiple stretch cycles with only minimal reduction in conductivity during stretch.
Another advantage of polymers over metals is the possibility of chemically functionalizing them with different molecules. Using a chemically defined, artificial biomatrix, it is possible to transform the materials from bioinert to highly cell-adhesive. This offers the possibility to optimize the materials depending on the specific application and the tissue type which they will interface. In the example shown the material were made adhesive for stem cells and neurons.
In perspective, we plan to develop materials that address not only the physicochemical mismatch but also the challenge of the functional mismatch between purely electrical signaling in metals and interconnected signaling (biomolecular and electronic) in living tissues. Using this approach, we expect to revolutionize bioelectronic and biomedical devices and further bridge the gap between living matter and electronics.
Afanasenkau D., Daria K., Vsevolod L., Tondera C., Gorsky O., Moosavi S., Pavlova N., Merkulyeva N., Kalueff A. V., Minev I. R., Musienko P. Rapid prototyping of soft bioelectronic implants for use as neuromuscular interfaces. Nature Biomedical Engineering, 4:1010-1022 (2020).
Athanasiadis M., Afanasenkau A., Derks W., Tondera C., Busskamp V., Bergmann O., Minev I. R. Printed elastic membranes for multimodal pacing and recording of human stem-cell-derived cardiomyocytes. npj Flexible Electronic, 4:16 (2020).
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Tondera C., Akbar T. F., Thomas A. K., Lin W., Werner C., Busskamp V., Zhang Y., Minev, I. R. Highly conductive, stretchable, and cell-adhesive hydrogel by nanoclay doping. Small, 15:27 (2019).
Tondera C., Wieduwild R., Röder E., Werner C., Zhang Y., Pietzsch J. In vivo examination of an injectable hydrogel system crosslinked by peptide–oligosaccharide interaction in immunocompetent nude mice. Advanced Functional Materials, 27:1605189 (2017).
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