117 research outputs found
Transport of small anionic and neutral solutes through chitosan membranes: Dependence on cross-linking and chelation of divalent cations
Chitosan membranes were prepared by solvent casting and cross-linked with glutaraldehyde at several ratios
under homogeneous conditions. The cross-linking degree, varying from 0 to 20%, is defined as the ratio between
the total aldehyde groups and the amine groups of chitosan. Permeability experiments were conducted using a
side-by-side diffusion cell to determine the flux of small molecules of similar size but with different chemical
moieties, either ionized (benzoic acid, salicylic acid, and phthalic acid) or neutral (2-phenylethanol) at physiological
pH. The permeability of the different model molecules revealed to be dependent on the affinity of those structurally
similar molecules to chitosan. The permeability of the salicylate anion was significantly enhanced by the presence
of metal cations commonly present in biological fluids, such as calcium and magnesium, but remained unchanged
for the neutral 2-phenylethanol. This effect could be explained by the chelation of metal cations on the amine
groups of chitosan, which increased the partition coefficient. The cross-linking degree was also correlated with
the permeability and partition coefficient. The change in the permeation properties of chitosan to anionic solutes
in the presence of these metallic cations is an important result and should be taken into consideration when trying
to make in vitro predictions of the drug release from chitosan-based controlled release systems
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