Surface-imprinted silica particles: The effects of added organosilanes on catalytic activity

Silicate surfaces were molecularly imprinted with a surfactant derivative of an α-chymotrypsin transition state analog (TSA) during particle formation in a water-in-oil microemulsion. The organosilanes N-(3-aminoethylaminomethyl)-phenyltrimethoxysilane (PEDA), carboxyethylsilanetriol (CTES), and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole (IPTES) were added along with tetraethoxysilane (TEOS) to imprint the chemical functionality of the imprint molecule. Surfaces imprinted with N-α-decyl-D-phenylalanine-2-aminopyridine enantioselectively catalyzed the hydrolysis of benzoyl-L-arginine-p-nitroanilide (L-BAPNA). No hydrolysis of D-BAPNA was observed. The catalytic activity of surface-imprinted particles formed with TEOS and PEDA was significantly greater than that of surface-imprinted particles formed with TEOS and IPTES. Particles formed with added 10 mol% (total silica) of PEDA hydrolyzed DL-BAPNA at a rate equivalent to that of surface-imprinted particles formed with the mixture of 5 wt% (total silica) of PEDA, CTES, and IPTES suggesting a cooperative effect with the organosilane mixture that promoted catalytic activity.