Sodium alginate–poly(vinyl pyrrolidone) pH-responsive hydrogels for controlled release of tinidazole

Abstract

Unlike conventional single polymer hydrogels, cross-linked sodium alginate/poly(vinyl pyrrolidone) provides greater structural integrity and pH-responsiveness. This synergy minimizes premature drug leakage in the upper gastrointestinal tract to ensure targeted drug release specifically to the colon. In this study, sodium alginate–poly(vinyl pyrrolidone) hydrogels were synthesized via an ionotropic method, by varying the polymer and CaCl₂ concentrations for colon specific controlled release of tinidazole. The hydrogels were characterized using Fourier transform infrared, field emission scanning electron microscopy, X-ray diffraction and thermogravimetric analysis to analyze the structural properties, surface morphology, crystalline structure and thermal stability. Based on swelling and porosity experiments, a 3 : 1 : 3% (w/v) proportion of sodium alginate/poly(vinylpyrrolidone)/CaCl₂ was determined as the optimal hydrogel composition for the in situ loading of 250 mg of tinidazole. The hydrogels exhibited good in vitro biodegradability and improved mechanical strength. The drug loaded hydrogel showed lower cumulative tinidazole release in acidic conditions (pH 1.2) in comparison to the drug release in simulated body fluid (pH 7.4), suggesting the stability of the hydrogels in the hostile environment of the stomach. Kinetic modeling indicated that the release profile was best fit with the Korsmeyer–Peppas model following swelling and diffusion controlled anomalous mechanism. The drug loaded hydrogel has shown strong antibacterial activity against B. fragilis. Thus, sodium alginate–poly(vinyl pyrrolidone) hydrogels have promising application for colon specific oral controlled release of tinidazole.