The diffusion coefficient of model drugs (Sodium benzoate, Lysozyme and Ribonuclease) through chitosan and N-alkyl chitosan membranes were measured by using ’lag time’ technique. The results indicate that the release mechanism for the drug with small molecular weight is predominantly of ’pore type’, and for the drug with high molecular weight is predominantly pf ’partition type’. The release of protein drug with higher hydrophobicity enhances as the size of N-alkyl group and its substitution degree of chitosan increase.
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