Vanillin van

Protocatechuic aldehyde (A‐o, Carl Roth), vanillin (van, Sigma–Aldrich), 3,5‐dihydroxybenzaldehyde (A‐m, Fischer), an aqueous solution (15 %) of polyallylamine with an average molecular weight of 15 000 g mol⁻¹ (PAAm, Polysciences, Inc.), carbon EQ‐AB‐520Y (C, MTI Corporation), carbon paper Spectracarb 2050A‐0550 (Fuel Cell Store), and the solvents ethanol (Fischer) and N‐methyl‐2‐pyrrolidone (NMP, PanReac AppliChem) were used as received.

To obtain the chitosan/bioglass composites in this research work, chitoceutical chitosan 95/2000 (degree of deacetylation ≥92.6%) (HMC+-Heppe Medical Chitosan GmbH company, Halle, Germany) was used. As a composites filler, a bioglass (BG) synthesized by the sol-gel method from the system of 25% CaO-70% SiO₂-5% P₂O₅ (ŁUKASIEWICZ Research Network—Institute of Ceramics and Building Materials, Biomaterials Research Group, Warsaw, Poland) was used. The particle size range of the bioglass was in the range: d(0.1) 7.1 µm; d(0.5) 59.9 µm; d(0.9) 215 µm. As stabilizing and crosslinking agents, 99% vanillin (VAN) (Sigma-Aldrich, Steincheim, Germany), ≥99.9% genipin (GEN) (Pol-Aura, Olsztyn, Poland), 5-water disodium β-glycerophosphate (BGP) (Sigma-Aldrich, Steincheim, Germany), 5-hydrate sodium tripolyphosphate (TPP) (Sigma-Aldrich, Steincheim, Germany), and 96% ethanol (96%EtOH) (POCH, Gliwice, Poland) were used. In addition, 99.8% acetic acid (POCH, Gliwice, Poland), NaOH (Chempur, Piekary Śląskie, Poland), PBS (phosphate buffer) (Pol-Aura, Olsztyn, Poland), and deionized water were also used.