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Adsorption of Chitosan onto Poly( D , L ‐lactic acid) Particles: A Physico‐Chemical Investigation
Author(s) -
Messai Isabelle,
Delair Thierry
Publication year - 2005
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200500073
Subject(s) - chitosan , adsorption , molar mass , chemistry , desorption , ionic strength , polymer chemistry , covalent bond , chemical engineering , polyelectrolyte , nuclear chemistry , organic chemistry , polymer , aqueous solution , engineering
Abstract Summary: Particles of poly( D , L ‐lactic acid) (PLA) obtained by emulsification‐diffusion were surface‐modified by adsorption of chitosan. Thus, positively charged biodegradable carriers were obtained as potential carriers for DNA. Various physico‐chemical parameters, susceptible to impact the elaboration of such colloids, were investigated. External parameters were the ionic strength and the nature of the buffer; pH was fixed at 4.5 in order to ensure the ionisation of both counterparts. Internal parameters were the molar mass of chitosan and its degree of acetylation (DA). Kinetically, the adsorption of chitosan was spontaneous. Adsorption isotherms of chitosan were established using two different assays for chitosan, one based on the formation of a covalent bond, and the other on the formation of an ion pair. Two adsorption regimes were evidenced in ammonium acetate buffer. The amount of adsorbed chitosan increased with its molar mass up to a limit due to steric hindrance and with the DA. The latter effect could be explained by a reduction of the molecular dimensions of chitosan with DA. On storing, desorption of chitosan was dependent on the molar mass of the polysaccharide and, to a lesser extent, on the DA.Complexation isotherm of chitosan onto PLA particles.