Conductive Tissue?!

It is very hard to connect solid-state electronics with organic tissue because of the toxicity, degradation.

Strakosas et al. [1] created a polymerization process which monomers polymerizes inside the tissue with enzymes. This is called enzymatic polymerization and it can provide seamless integration with man-made material and neural tissue.

Solid-state electronics can be made conductive but they cannot reach to deep neurons or compatible with tissue. In order to reach them non-invasively, material must be with low viscosity. After it seeps, it must be hardened with external or internal ways.

Figure 1. Conductive tissue introduction [1]

Strakosas et al. [1] introduced peroxides with the solution. In short, solution contains monomer, oxidase enzymes, or lactate oxidase, horseradish peroxidase embedded in polymer matrix. It is enzymatically polymerized by peroxides in the presence of hydrogen peroxide. Polymer was polymerized inside the brain tissue. After giving current to electrodes, increase in current exhibited in sigmoidal behavior after 500 seconds glucose addition.

But in long terms [1], monomer (2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thiophene (ETE for short)) reacts with the carboxyl groups of ETE derivative with a 2-ethoxyacetic acid sodium salt side chain, creating an ester intermediate. Intermediate reacts with poly-L Lysine and hydroxyl (-OH) groups of poly (Vinyl Alcohol) and other amines and alcohol groups on the tissue. This process happens outside of tissue.

Then [1], gel introduced to tissue for polymerization. Metabolites from the tissue reacts with solution, creates hydrogen peroxide in the medium of oxygen. Horseradish peroxide converts hydrogen peroxide to water. ETE monomers are converted to radicals which starts the polymerization. Reached conductive polymer takes the shape of a gel and stays conductive within neural tissue.

Figure 2. Injected gel and polymerized gel after 10 minutes [1]

The conductive tissue was tried on zebrafish and leech experiments and gave promising results. In zebrafish, the polymer has been experimented on tails. It seemed that glucose and lactate concentration was the important limiting factor in the study.

This study can pave the way for a human-machine interface. I don’t know if it is a good or bad improvement. With conductive tissues, the human brain can be affected externally. This can and will create problems if we don’t act with caution. We must also not forget that all technology usage must be considered before using.

As Feynman said after the Challenger incident:

For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.

References

[1] X. Strakosas et al., “Metabolite-induced in vivo fabrication of substrate-free organic bioelectronics”, doi: 10.1126/SCIENCE.ADC9998.