Chiral, pH-sensitive polyacrylamide hydrogels: Preparation and enantio-differentiating release ability

Abstract

Both pH-sensitive hydrogels and chiral hydrogels have evoked large interest in recent years. In the study, we designed and prepared a novel type of hydrogels simultaneously showing pH-sensitivity and chirality. Such hydrogels were prepared by free radical co-polymerization using N-acryloyl-l-alanine as chiral hydrophilic monomer and octadecyl acrylate as hydrophobic monomer, with K2S2O8 as initiator and N,N′-methylenebisacrylamide as chemical cross-linking agent. The obtained hydrogels exhibited remarkable pH-sensitive swelling ability in water. The optical activity of the hydrogels was characterized using circular dichroism spectroscopy. More interestingly, the hydrogels showed enantio-differentiating release ability towards proline enantiomers, in which d-proline was preferentially released. The hydrogels also demonstrated remarkable enantio-differentiating release ability toward chiral drug ibuprofen.