Quantitative determination of carboxymethyl chitin in polymer-coated liposomes

A simple turbidity method for the quantitative determination of carboxymethyl chitin (CM-chitin) in coated liposomes has been developed. Isopropanol:buffer (1:1 v/v) was selected as a good solvent system for dimyristoyl-, dipalmitoyl-, or egg phosphatidylcholines but not CM-chitin. The turbidity of CM-chitin in this solvent system was spectrophotometrically determined at 400 nm without significant interference by these phosphatidylcholines. The dependence of turbidity on the CM-chitin concentration, pH, and ionic strength were determined. It was found that analyses of the coating efficiency of dipalmitoylphosphatidylcholine liposomes by CM-chitin were reproducible within the specified ranges of formulation conditions and enabled differentiation of the effect of order of CM-chitin addition on the coating efficiency.