title: Transport of small anionic and neutral solutes through chitosan membranes: dependence on cross-linking and chelation of divalent cations.
abstract: 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.
authors.affiliation: Department of Polymer Engineering, 3B's Research GroupBiomaterials, Biodegradables and Biomimetics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal. ricardosilva@dep.uminho.pt
authors.forename: Ricardo M P
authors.initials: RM
authors.lastname: da Silva
authors.forename: Sofia G
authors.initials: SG
authors.lastname: Caridade
authors.forename: Julio
authors.initials: J
authors.lastname: San Román
authors.forename: João F
authors.initials: JF
authors.lastname: Mano
authors.forename: Rui L
authors.initials: RL
authors.lastname: Reis
mesh_terms: D000838:Anions; D001672:Biocompatible Materials / Q000737:chemistry; D002412:Cations; D002614:Chelating Agents / Q000737:chemistry; D048271:Chitosan / Q000737:chemistry*; D004058:Diffusion; D005976:Glutaral / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances / Q000737:chemistry; D015233:Models, Statistical; D010539:Permeability; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000838:Anions; D001672:Biocompatible Materials; D002412:Cations; D002614:Chelating Agents; D046911:Macromolecular Substances; D012997:Solvents; D014867:Water; D048271:Chitosan; D005976:Glutaral