Development of silica-based conductive hydrogels for biomedical application

For potential use as electrically conductive materials in biomedicine, hydrogels of unmodified and organically modified silica with a pH close to neutral were synthesized by the sol-gel method. The effects of synthesis conditions (concentration of HCl as a catalyst of silica sol formation, order of mixing of silica sol and neutralizing agent (phosphate buffer solution, pH 7.4)), as well as modification of the silica matrix with organic groups (aminopropyl and mercaptopropyl) on the most important characteristics of hydrogels for the practical application, namely, electrical conductivity and viscoelastic properties (complex viscosity, storage and loss modules), were studied. It was shown that the synthesized hydrogels have ionic conductivity (15.4–18.2 mS cm⁻¹) and exhibit pseudoplasticity, as well as solid-like behavior, and their 3D structure is stable over the frequency range 0.1–10 Hz. In contrast to the minor effect of HCl concentration, adding the phosphate buffer solution to silica sol and silica matrix modification with the organic groups led to an increase in the viscoelastic characteristics of the hydrogels but a decrease in their ionic conductivity. The obtained data showed that the synthesized silica hydrogels are promising platform for development new conductive hydrogel materials for various biomedical applications.