Kinetic aspects of polyelectrolyte adsorption: adsorption of chitin derivatives onto liposomes as a model system.
Carboxymethylchitin (CMC) and Carboxymethyl/Glycolchitin (CO) have been adsorbed onto liposomes at physiological ionic strength (I) and pH using phosphate buffer saline (PBS, I = 154 mM, pH = 7.4). Adsorption isotherms at different polymer weight average molecular weights (Mw), for Positive ([+]) or high surface affinity liposomes (DSPC:CHOL:DMTAP, 5:4:1), and Neutral ([N]) or low surface affinity liposomes (DSPC:CHOL, 1:1), have been obtained at T = 25 degrees C. For all CMCs, the adsorbed amount increases with polymer concentration ([P]zero) and no true plateau is observed. The CMC Mw = 4.19 x 10(5) adsorbed on a positive surface fits Langmuir kinetics with maximal coverage gamma max = 325.4 micrograms/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 (Rg) is inferior to the amount adsorbed. This fact in conjunction with the dependence of gamma max on the number of adsorption shots, suggests that the adsorption is not thermodynamically but kinetically controlled.
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Artificial Cells and Organs Research Centre, McGill University, Montreal, Quebec, Canada.
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D000327:Adsorption; D001704:Biopolymers / Q000493:pharmacokinetics; D001802:Blood Substitutes / Q000493:pharmacokinetics*; D002686:Chitin / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D048271:Chitosan; D007700:Kinetics; D008081:Liposomes / Q000493:pharmacokinetics*; D008954:Models, Biological
D001704:Biopolymers; D001802:Blood Substitutes; D008081:Liposomes; D002686:Chitin; C044872:O-(carboxymethyl)chitin; D048271:Chitosan; C031610:glycolchitin