BIOADHESION OF HYDRATED CHITOSANS - AN IN-VITRO AND IN-VIVO STUDY

The (bio)adhesivity of several chitosan chloride samples was screened in vitro and compared with hydroxypropyl methylcellulose (HPMC), Carbo pol 934P and polycarbophil by a force of detachment method. This revea led differences between samples, but was judged to be insufficient to describe the bioadhesive behaviour of fully hydrated chitosan. Therefo re, an ex vivo method was designed, where freshly excised cattle corne as were created with tritiated chitosan in solution. The contact time, pH, ionic strength and chitosan molecular weight were investigated by means of factorial design, and were shown to have significant effects on the adsorption. In addition, interactions were seen between the pa rameters. These effects were not seen when chitosan was incubated with polycarbonate membranes instead of corneas. It is concluded that full y hydrated chitosan has a specific bioadhesive activity towards biolog ical surfaces. In the in vivo study, liposomes and chitosan-coated lip osomes containing I-125-labelled bovine serum albumin (BSA) as a marke r were applied to the eyes of anaesthetised rats and their retention a t 10, 30 and 90 min compared. Both formulations showed significantly l onger retention than a solution of the free I-125-BSA, but coating the liposomes with chitosan did not significantly improve their retention . It is concluded that the adhesive interaction between chitosan and a biological substrate is dependent on formulation factors as well as t he chitosan quality. Copyright (C) 1997 Elsevier Science B.V.