The importance of standardization of carboxymethylchitin concentration by the dye-binding capacity of alcian blue before adsorption on liposomes

Adsorption of chitin derivatives onto liposomes: optimization of adsorption conditions

A 2(4) factorial design is used to optimize the adsorption conditions of the hydrophilic anionic polyelectrolytes. Carboxymethylchitin (CMC) and Carboxymethyl/Glycolchitin (CO) onto liposomes at physiological ionic strength (I) and pH using phosphate buffered saline (PBS, I = 154 mM, pH = 7.4). Positive ([+]) or high surface affinity liposomes (DSPC:CHOL:DMTAP, 5:4:1), and Neutral ([N]) or low surface affinity liposomes (DSPC:CHOL, 1:1) were used as adsorption surfaces. Results of the calculations of the main effects indicate that polymer molecular weight (mwt), Surface Affinity (S), Number of Adsorption Shots (Sh), Temperature (T), and the combinations mwt x S, mwt x Sh are the most important process parameters. Results of a study conducted at T = 37 degrees C show that no loss occurs from the positive surface at the highest particle concentration, Np = 4.043 x 10(11). Finally, the extent of polymer-induced particle aggregation is decreased when the diameter of the uncoated liposomes is doubled from 0.22 to 0.45 micron. These results are as expected, given the stiffness and the dimensions of the macromolecules.

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.