KINETIC ASPECTS OF POLYELECTROLYTE ADSORPTION - ADSORPTION OF CHITIN DERIVATIVES ONTO LIPOSOMES AS A MODEL SYSTEM

Carboxymethylchitin (CMC) and Carboxymethyl/Glycolchitin (GO) have bee n adsorbed onto liposomes at physiological ionic strength (I) and pH u sing phosphate buffer saline (PBS, I = 154 mM, pH = 7.4). Adsorption i sotherms at different polymer weight average molecular weights (M-w), for Positive ([+]) or high surface affinity liposomes (DSPC:CHOL:DMTAP , 5:4:1), and Neutral ([NI) or low surface affinity liposomes (DSPC:CH OL, 1:1), have been obtained at T = 25 degrees C. For all CMCs, the ad sorbed amount increases with polymer concentration [P](o)] and no true plateau is observed. The CMC M-w = 4.19x10(5) adsorbed on a positive surface fits Langmuir kinetics with maximal coverage Gamma(max) = 325. 4 mu g/mg (polymer/lipid), and inverse of equilibrium constant K = 4. 743 x 10(-4) mg/ml. For all isotherms the predicted amount of polymer needed to coat the entire surface based on the Radius of Gyration (R-g ) is inferior to the amount adsorbed. This fact in conjunction with th e dependence of Gamma(max) on the number of adsorption shots, suggests that the adsorption is not thermodynamically but kinetically controll ed.