Cytochrome c adsorption on various poly-L-glutamic acid-containing calcium phosphate particles

We synthesized novel materials at different temperatures with two types of poly-L-glutamic acid--poly-alpha-glutamic acid and poly-gamma-glutamic acid--to confirm the effect of poly-L-glutamic acid, which exhibits hydroxyapatite (HAp) (pGlu-HAp) crystallinity, on particle morphologies and cytochrome c (Cyt c) adsorption abilities. Through hydrothermal treatment, rod-like particles, as well as thin sheet-like particles, grew along the c-axis. Moreover, the crystallinity of particles was found to improve with an increase in the reaction temperature from 60 degrees C to 120 degrees C. The Cyt c adsorption ability of pGlu-HAp, rather than the crystallinity of calcium phosphate, was affected by the peptide structure. Furthermore, pGlu-HAp was used effectively for Cyt c adsorption with not only the carboxyl residues of side chains in peptides but also mesopores in the range of 3-30 nm. In addition, the catalytic activity of Cyt c adsorbed on the particles containing poly-alpha-glutamic acid retained high activity and was similar to that exhibited by native free Cyt c. The graphene oxide/imogolite/Cyt c@pGlu-HAp-modified glassy carbon electrode showed good electrocatalytic responses as a candidate for a H2O2 biosensor. According to these results, the pGluHAp materials prepared in this study can act as useful enzyme carriers and electrodes, because they maintain high enzyme activity when adsorbed on particles.