Mucoadhesion of polyamphoteric hydrogels synthesized from acrylic acid and N,N-dimethylaminopropyl acrylamide

Abstract Bioadhesive polymeric hydrogels capable of firm adhesion to various biological tissues have acquired considerable attention due to their significance in medicine and dentistry. Thus far many types of bioadhesive hydrogels have been investigated using different polymers such as polyacrylates, poly(ethylene glycol)s, and the derivatives of polysaccharides and proteins, while less attention has been paid to polyamphoteric properties of cross-linked polymer networks. The aim of this study is to investigate the bioadhesive properties of polyamphoteric hydrogels synthesized by copolymerizing acrylic acid with N,N-dimethylaminopropyl acrylamide in the presence of N,N′-methylenebisacrylamide. Tissue adhesion of hydrated gels was evaluated in vitro using the excised porcine intestine as a substrate, and the data were compared with that measured for the pure poly(acrylic acid) hydrogel that is a bioadhesive system extensively studied ever. In this study, it is demonstrated that the incorporation of a small fraction of the cationic monomer to a poly(acrylic acid) hydrogel gives rise to the formation of polyamphoteric hydrogels that exhibit firm adhesion toward mucosa. The results of the mechanistic study revealed that the adhesion enhancement by cation incorporation is primarily due to the increased density of carboxylic acids that are capable of interacting with mucosal components. Furthermore, it was suggested that the dynamic behaviors of the polymer segments have an additional effect on the enhanced mucoadhesion.