Effect of salt forms and molecular weight of chitosans on in vitro permeability enhancement in intestinal epithelial cells (Caco-2).

The purpose of this study was to investigate the effect of molecular weight (MW) and salt forms of chitosans (aspartate; CS A, glutamate; CS G, lactate; CS L and hydrochloride, CS HCl) on the transepithelial electrical resistance (TEER) and permeability of Caco-2 cells monolayer, using fluorescein isothiocyanate dextran 4000 (FD-4) as the model compound for paracellular tight junction transport. Chitosan salts were prepared by spray-drying method. FTIR and solid-state (13)C NMR spectra showed the functional groups of salts in their molecular structures. Salt form, MW of chitosan, and amount of chitosan influenced the permeation-enhancing effects. These studies showed that chitosan salts appeared to increase cell permeability in a dose-dependent manner and caused relatively reversible effects only at the lower doses of 0.001-0.01% w/v. As the MW of chitosan increased from 20 to 460 kDa, the reduction in TEER significantly decreased in the following order: 20 < 45 < 200 < 460 kDa, observed in CS L and CS HCl. In CS A and CS G, the decrease in TEER was not significantly different in all MW because both chitosan salts showed rapid reduction in TEER within 20 min after the start of the experiment. Among chitosan salts, CS A was the most potent absorption enhancer in acidic (pH 6.2) environment. Cytotoxicity of chitosan salts was concentration dependent and varied slightly among the salt forms of chitosan used. CS HCl (MW 45 kDa) was the most toxic having an IC50 of 0.22 +/- 0.06 mg/mL. The ranking of chitosan salts cytotoxicity was CS HCl > CS L> CS G > CS A.