Biomimetic fabrication of hydroxyapatite-polysaccharide-formate dehydrogenase composite capsules for efficient CO(2)...

In this study, a novel kind of hydroxyapatite-polysaccharide capsules was prepared through a bio-inspired process in simulated body fluid for efficient encapsulation of formate dehydrogenase. In this process, a thin alginate/chitosan film formed immediately around the capsules coupled with in situ precipitation of hydroxyapatite when alginate HPO(4)(2-)-stock solution droplets were added into chitosan Ca(2+)-stock solution. The biomineralization of hydroxyapatite was mimicked by the counter-diffusion system in which calcium ions and phosphate ions migrated into the alginate/chitosan film from opposite directions. Formation of capsule was confirmed by Zoom Stereo Microscopy, the surface morphology of the capsule was characterized by SEM, the surface element composition of capsules was analyzed by EDX and the pore size distribution of capsule shell was determined by BET. As compared to the free formate dehydrogenase, hydroxyapatite-polysaccharide-formate dehydrogenase composite capsules exhibited significantly higher activity and storage stability in a broader temperature and pH range when converting CO(2) to formic acid.