Development and cytotoxicity evaluation of a cylindrical pH-responsive chitosan-genipin hydrogel for the oral delivery of diclofenac sodium

A cylindrical hydrogel composed of chitosan (1.250 % w/v) and genipin (0.185 % w/v) was developed for the oral delivery of diclofenac sodium (0.250 % w/v). The produced hydrogel was a dosage form with a porous structure and pH-dependent swelling and release profiles. Dissolution studies revealed 10 +/- 0.4 % drug release at pH 1.2 after 2 h and 70 +/- 13.5 % at pH 6.8 at 5 h. Release at gastric media simulation was 6.1 +/- 2.0 % after 2 h at pH 3.0 and 88.2 +/- 5.0 % after 2 h at intestinal fluid simulation at pH 7.0. The hydrogel components did not induce in vitro cytotoxic effects in MRC5 and Caco-2 cells at the two lowest concentrations tested by MTT assay. Cellular viability was between 75 +/- 5.9 % and 106 +/- 3.7 % for individual components and between 71 +/- 4.1 % and 106 +/- 15.1 % for fractions taken from the dissolution assays. Our findings suggest that the proposed formulation could be a potential candidate for a gastro-resistant drug delivery system of diclofenac sodium.