Evaluation of mucoadhesiveness of polymers by BIACORE method and mucin-particle method.

To evaluate the reliability of the BIACORE method as a useful method for measuring the mucoadhesive interaction between chitosan and mucin, the mucin-particle method was used for comparison. In this study, the adhesivities of different-molecular-weight chitosans (chitosan Mw. 150,000, CS; low-molecular-weight chitosan, LCS) and hydrophobically modified chitosans (dodecylated CS, d-CS; dodecylated LCS, d-LCS) to mucin were determined. The BIACORE method showed that CS, LCS and d-CS could interact with mucin based on the increased resonance unit (RU) response after mucin was passed over the chitosans-immobilized sensor chip surface. Sensorgrams obtained from the interaction between these polymers and mucin also indicated the rate and strength of binding reaction. The rate and strength were higher for unmodified chitosans than hydrophobically modified chitosans. The simple in vitro mucoadhesive test or mucin-particle method revealed that the turbidity of unmodified chitosan/mucin mixtures was higher than that of dodecylated chitosans for all concentration of chitosans and mucin. The results from both BIACORE and the mucin-particle method implied that hydrophobic modification of chitosan reduced its adhesivity to mucin. The results from these two methods corresponded well. Therefore, the BIACORE method has promised as an alternative method for evaluating the adhesivity of adhesive polymers to mucin.