A novel pH-sensitive gelatin-DNA semi-interpenetrating polymer network hydrogel

Gelatin and DNA were mixed together in various ratios followed by the addition of glutaraldehyde as a cross-linker. FT-IR spectroscopy confirmed the formation of a semi-interpenetrating polymer network (semi-IPN) between the gelatin and DNA. The gelatin-DNA semi-IPN hydrogel underwent, reversibly, remarkable changes in swelling degree in response to the variation of pH, In the low-pH range, the hydrogel showed a lower swelling degree; with an increment in pH, the hydrogel was highly swollen, which is considered to originate from the complexation and de-complexation between gelatin and DNA, as was verified by turbidity measurements. Higher contents of DNA result in an increase in the swelling degree, which is presumably due to the easy outward expansion of free DNA moieties. The permeability coefficient, P, for a model molecule, cimetidine, through the semi-IPN hydrogel membranes was determined in pH 1.0 and pH 12.0 buffer solutions. The results show that the permeation of cimetidine is responsive to pH change, and an evident variation in the P values occurs in response to the pH of the media.