Modification of biopolyelectrolytes for bioadhesive applications

Abstract

Biomimetic research on the development of bioadhesives mimicing the adhesive proteins secreted by blue mussels have become very popular in the recent years. The most important feature of the adhesive proteins is that they can stick to any type of surfaces in dry or wet environment. Furthermore, these proteins can preserve their bulk adhesive properties over time in the presence of water in which most adhesives fail to manage. 3,4-dihydroxy-L-phenylalanine (L-DOPA) is an aminoacid found in the adhesive proteins of marine mussels. L-DOPA is the most abundant molecule at the interface of adhesion and the catechol group of DOPA is believed to be the key funtional group in mussel attachment. There have been numerous studies on catechol functionalization of polymers to mimic the adhesive feature of mussel adhesive proteins. However, the advantage of our method is that the polymers were modified by forming strong amide bond, which is more stable against hydrolysis, using catechol containing molecules. In this study, the catechol modification of two biopolyelectrolytes; hyaluronic acid (HA) and chitosan (CHI) with L-DOPA-Methyl ester and 3,4-dihydroxyhydrocinnamic acid (DOHA), respectively, was achieved via carbodiimization of active esters. The modification was confirmed with 1H-NMR analysis, UV spectroscopy and gelation with periodate. The degrees of modification (% by mole) of polymers were calculated by UV-Vis spectroscopy. Potentiometric titrations were also carried out to investigate the effect of modification on pKa of biopolymers. Higher pKa values of modified polymers than that of unmodified ones also confirmed the modification.