Preparation and optimization of tetraethyl orthosilicate cross-linked chitosan-guar gum-poly(vinyl alcohol) composites reinforced with montmorillonite for sustained release of sitagliptin.

Development of efficient drug carriers has become an integral part of advanced drug delivery systems. This work aims at developing composites by adopting an economically viable method for sustained release of anti-diabetic drug sitagliptin - a potent and selective dipeptidyl peptidase-IV inhibitor. To combat the harsh environment of gastrointestinal tract, the composite (F13) was prepared using biodegradable polymers namely chitosan, guar gum and poly(vinyl alcohol) with montmorillonite clay as nano-filler and tetraethyl orthosilicate as the cross linker. The composites were characterized using FT-IR, XRD, DSC and SEM techniques. Physical properties such as thickness, swelling capacity, folding endurance and water solubility were studied. In vitro analysis of composites (F17, F19 and F20) in simulated gastric medium showed <14 % cumulative release in 2 h while a sustained release was observed in simulated intestinal medium. Drug release kinetics was investigated using five mathematical models namely zero order, first order, Higuchi, Hixon-Crowell and Korsemeyer-Peppas wherein the latter was the best fit model (R2, 0.969). Antimicrobial studies of drug free composite (F13) revealed good activity against bacteria as well as fungi. The results implied that the composites were pH sensitive and could serve as a potential choice for sustained release of drugs.