Carbonic anhydrase conjugated to nanosilver immobilized onto mesoporous SBA-15 for sequestration of CO2

Abstract

Abstract Human carbonic anhydrase (HCA) was conjugated via electrostatic interactions onto silver nanoparticles confined to amine-functionalized mesoporous SBA-15. Three amine compounds were tested for their effectiveness in immobilizing silver nanoparticles: tris(2-aminoethyl)amine (TAEA), tetraethylenepentamine (TEPA), and octa(aminophenyl)silsesquioxane (OAPS). The enzymatic activities of the free and nanosilver conjugated HCA were assessed by measuring the hydrolysis of p-nitrophenylacetate (p-NPA) and the hydration of CO 2 , which was sequestered as CaCO 3 . The CO 2 conversion efficiency was calculated using ion chromatography methods, and CaCO 3 formation was observed by polarized light microscopy. Precipitated CaCO 3 was characterized by XRD and FE-SEM. After 30 cycles, the silver conjugated HCA showed the highest operational stability, and the CO 2 capture efficiency was ∼25 fold higher than that of free HCA. Storage stability studies suggested that conjugated HCA retained nearly 87% of its activity after 30 days. The results demonstrated that immobilized HCA was reusable and stable under storage conditions. Thus, this nanobiocatalyst is a suitable candidate for the capture and sequestration of CO 2 .