Structure–activity relationships of methylated N-aryl chitosan derivatives for enhancing paracellular permeability across Caco-2 cells

The aim of this study was to investigate three kinds of methylated chitosan containing different aromatic moieties; methylated N-(4-N,N-dimethylaminobenzyl) chitosan (TM-Bz-CS), methylated N-(4-N,N-dimethylaminocinnamyl) chitosan (TM-CM-CS) and methylated N-(4-pyridylmethyl) chitosan (TM-Py-CS), on the paracellular permeability of Caco-2 cell monolayers and their toxicity towards the cell lines. The factors affecting epithelial permeability were evaluated in intestinal cell monolayers of Caco-2 cells using the transepithelial electrical resistance (TEER) and permeability of Caco-2 cell monolayers, with fluorescein isothiocyanate dextran 4400 (FD-4) as a model compound for paracellular tight junction transport. The results revealed that methylated chitosan containing different aromatic moieties showed the different absorption enhancing ability. The rank of enhancing paracellular permeability was TM65CM50CS > TM56Bz42CS > TM65CS > TM53Py40CS. The cytotoxicity of these modified chitosans on Caco-2 cells was also studied by MTT assay where the TM53Py40CS exhibited less toxicity than other derivatives. These studies demonstrated that the chemical structure and the positive charge location play an important role for absorption enhancement and cytotoxicity.