Thesis presented October 23, 2020

Abstract:
Within the framework of the ANR biopile abiotic implantable (Imabic) project coordinated by INAC, this thesis work aimed to optimize the performance and stability of a biocathode based on iron and nitrogen-doped graphene (Fe/N-rGO). We have therefore manufactured and characterized different types of biocathods involving different binders in order to provide electrode architectures that are best suited to allowing the species consumed and produced during the reaction to be distributed within them. In these studies, one binder is distinguished from the others, the chitosan binder. In addition, once this binder was cross-linked using Genepine, we observed a stability of electrochemical performance over time, limiting the loss of current density to 5% of a biocathode that had been stored in physiological condition for 27 months. During this project, we also developed a new electrode manufacturing process involving freeze-drying, this process allows an increase in the porosity of the electrodes and improves the mass current densities by a factor of 4 compared to those provided by the compressed electrodes. However, this improvement is made at the expense of mechanical resistance and the resulting electrodes become more sensitive to shocks, in order to provide a solution to this new problem we have optimized our process by adding a carbon support to our freeze-dried biocathodes, allowing to improve the mechanical hold while maintaining the electrochemical properties. In the second part of this manuscript, we looked at the biocompatibility of our biocathode system. We carried out preliminary cell culture tests of the different materials likely to make our biocathode in the presence of mouse fibroblast cells: 3T3-L1 cells. These tests demonstrate a normal proliferation for the different binders used, but demonstrate a disrupted viability of the cells with respect to the presence of the catalyst at 10%. On the basis of these results, the Grenoble Ethics Committee approved the use of rat implants. Two biocathods from the compression process and two biocathods from the freeze-drying process were implanted in two rats that showed no signs of suffering and natural behaviour during the 1-month implantation period. After autopsy, no organ was affected by the presence of electrodes, on the other hand, on the four implants, three were coated with biological tissue resulting from implantation. Histological analysis of these tissues showed a fat composition for two of them and an inflammatory zone between 20 and 50 µm, consisting of fibroblastic cells, macrophages and polynuclear. We also observed that the tissues were highly vascularized.

Keywords:
implantable, biocathode, abiotic, biofuel cell, optimisation

On-line thesis.