Novel pH responsive supramolecular hydrogels of chitosan hydrochloride and polyoxometalate: In-vitro, in-vivo and preliminary safety evaluation

In the current study, electrostatically-driven pH responsive, supramolecular hydrogels of the trilacunary Wells-Dawson-type 15-tungsto-2-phosphate polyanion (P2W15) and chitosan hydrochloride (ChCl) were prepared, using methacrylic acid as pH responsive agent using benzoyl peroxide (BPO) as initiator. The prepared hydrogels were characterized by FT-IR, SEM, XRD and thermal analyses (TGA-DSC). The swelling and pH based P2W15 release profile of the hydrogels showed maximum swellability and release at pH 7.4. Different mathematical models were applied, showing that P2W15 release followed supercase transport-II mechanism and zero-order kinetics. The cytotoxicity results showed that free and embedded P2W15 exhibited dose-dependent cytotoxicity against cancer cell lines (MCF-7; HeLa) with minimal effects on normal cells (Vero). The developed hydrogels were administered to the rabbits for determining the pharmacokinetic behavior of the polyanion. Moreover, the developed hydrogel system as well as polyanion concentration used were also checked for its oral tolerability and safety evaluation in rabbits. The histopathological studies, serum chemistry (except blood glucose level) and hematological investigations exhibited that administered hydrogel suspension at maximal tolerable dose (4000 mg/kg body weight) and polyanion concentration used (20 mg) were safe from in-vivo point of view. The developed hydrogels exhibited desirable qualities of a drug delivery system that can be used for the delivery of the embedded polyanion.