PERIODIC MESOPOROUS ORGANOSILICAS WITH CHEMICALLY IMMOBILIZED β CYCLODEXTRIN MOIETIES FOR BILE SALTS SORPTION

Abstract

Mesoporous silicas of MCM‑41 type with surface silanol, 3-aminopropyl, and β‑cyclo­dextrin‑containing groups were prepared by hydrothermal‑assisted base‑catalyzed sol‑gel condensation of structure-forming silanes in the presence of micelles of long‑chain quaternary ammonium salt. Characterization of synthesized silica materials was realized by low‑tempe­rature nitrogen adsorption‑desorption and chemical analysis of surface layer. It was found that addition of ‑cyclodextrin‑containing silane into the sol‑gel reaction mixture causes formation of MCM‑41‑type organosilica with higher surface area and hexagonally arranged uniform mesoporous structure. Sorption ability of synthesized silica materials towards sodium cholate and sodium taurocholate was studied in dependence of solution pH and concentration. It was found that sorption increases due to chemical immobilization of oligosaccharide moieties in the surface layer of silica, and achieves maximal values in the pH regions of molecular forms of bile acids prevailing. Experimental sorption results were analyzed using Freundlich, Redlich - Peterson, and Brunauer - Emmett - Teller models. The formation of island-type structures of bile salts with β‑cyclodextrin-containing surface sorption centers due to cooperative interactions between sorbate moieties was proved.