Polysaccharide-based smart copolymeric hydrogel from chia seeds: Fabrication, pH-responsiveness, sustained drug release, and acute toxicity studies

Abstract

Herein, a polysaccharide-based mucilage isolated from chia (Salvia hispanica) seeds was treated with methacrylic acid (MA) and N,N'-methylenebisacrylamide (MBA) to fabricate a smart copolymeric hydrogel as a pH-responsive sustained release drug delivery system (DDS). The Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) verified the successful grafting of MA on the backbone of chia seeds polysaccharide (CS) and increased stability of the synthesized copolymeric hydrogel (CS-co-MA) over CS, respectively. The scanning electron microscopy (SEM) images demonstrated the porous structure of CS-co-MA. The Powder X-ray diffraction (PXRD) analysis witnessed the successful entrapment of crystalline drug, i.e., diclofenac sodium (DS), in the amorphous polymeric network of CS-co-MA hydrogel. A high gel fraction and a proportionally small sol fraction are due to the increased concentrations of CS, MA, and MBA. By increasing the concentration of CS, the porosity, swelling capacity, and drug loading onto CS-co-MA discs were found to increase. However, once the MA and MBA concentrations increased, the aforementioned features decreased. All formulations of CS-co-MA showed modest swelling at pH 1.2, while excellent swelling at pH 7.4, following second-order kinetics. The sustained release of DS from DS-loaded formulations of CS-co-MA, i.e., DS-CS-co-MA, depends on the pH of the dissolution media, the swelling capacity of CS-co-MA, and the concentrations of CS, MA, and MBA. The DS release followed first-order kinetics and a non-Fickian (anomalous) diffusion mechanism. The non-toxic nature of the CS-co-MA was ascertained through an acute toxicity study performed on the Swiss albino rats.

Keywords: Glucoxylan; Hydrogel; Polysaccharides; Swelling deswelling; pH-responsiveness.