Preparation and characterization of chitosan-co-acrylamide hydrogels for controlled drug delivery

Abstract This study developed a chitosan-co-acrylamide hydrogel for controlled, pH-responsive delivery of venlafaxine hydrochloride. Hydrogels were synthesized via free-radical polymerization of chitosan and acrylamide, cross-linked with N,N′-methylenebisacrylamide (MBA), and initiated with ammonium persulfate (APS) and sodium metabisulfite (SMS). Three formulations with varying chitosan content (1.0, 0.2, and 0.1 g) were prepared and characterized by FTIR, SEM, TGA, DSC, and XRD to confirm structural integrity and thermal stability. Swelling was pH-dependent, with maximum uptake at pH 7.4 and minimum at pH 1.2. Drug release followed the same trend, with slower release at pH 1.2 and faster release at pH 7.4, attributed to greater hydration and expansion of the polymer network at higher pH; complete release occurred within 36–42 h, following zero-order kinetics ( R 2 ≈ 0.9998). Drug loading, performed by immersing dried hydrogel discs in 50 mL of venlafaxine hydrochloride solution (1 mg/mL) for 24 h at 37 °C, yielded encapsulation efficiencies of 92.00–99.23 %. Batch B (0.2 g chitosan) showed the highest encapsulation efficiency (99.23 %) and the most favorable balance of swelling, drug loading, and sustained release, identifying it as the optimum formulation for oral venlafaxine delivery.