Imprinting of Stöber particles for chirally-resolved adsorption of target monosaccharides and disaccharides

A simple, inexpensive, and tunable imprinting technique to produce nonporous particles for selective chirally-resolved adsorption of saccharides has been developed. A sugar-based surfactant is added early in the Stöber particle synthesis process (60 seconds after the silica precursor addition) to create molecularly imprinted sites on the surface of the silica particles which are sensitive to the chirality of carbohydrate adsorbates. Mixtures of hexadecyltrimethylammonium bromide (CTAB), and n-octyl-β-d-glucopyranoside (C8G1) or n-dodecyl-β-d-maltopyranoside (C12G2) are employed to target adsorption of d-glucose or d-maltose, respectively. The adsorption of d-glucose on these imprinted materials is enhanced by almost 1.5 times over adsorption of other hexoses like d-mannose and d-galactose which differ by a change at only one chiral center. d-Glucose showed a difference in adsorption of greater than 3 times over the enantiomer l-glucose. Materials imprinted to target d-maltose showed nearly 5 times enhancement in adsorption of d-maltose over cellobiose at the lowest tested concentration. This study shows that a direct molecular imprinting approach of the surface of freshly prepared, soft silica particles can yield particles that exhibit preferential adsorption for a chiral target over similar molecules differing by one or more chiral centers, or by the anomeric attachment within polysaccharides.