Citric acid crosslinking of arabinoxylan engenders a stimuli-responsive hydrogel as a smart material for intelligent drug delivery

Abstract

The use of polysaccharide-based hydrogels in the development of novel drug delivery systems (DDSs) has increased steadily due to their swellable nature, pH-responsive behavior, biodegradability, biocompatibility, and low toxicity. Arabinoxyan (AX) was obtained using a hot-water extraction approach and esterified with three different concentrations, i.e., 2.5, 5, and 10% of citric acid (CA) in the presence of 4-dimethylaminopyridine (DMAP) as a catalyst to get CA crosslinked AX derivatives (CL-AX-1, CL-AX-2, and CL-AX-3). Fourier transform infrared (FTIR) spectroscopic analysis of AX and CL-AX-2 confirmed the esterification of AX. Scanning electron microscopy (SEM) analysis confirmed the superporous morphology of CL-AX-2, characterized by the presence of interconnected microscopic channels. The CL-AX-2 exhibited stimuli-responsive behavior, with swelling observed in the order: distilled water (DW) > pH 7.4 > pH 6.8 > pH 1.2. The swelling kinetics followed a second-order kinetic model. At pH 6.8, CL-AX-2 sustained the release (92%) of valsartan for up to 24 h, whereas at pH 1.2, nominal drug release (16%) was observed even after 24 h. Valsartan was released using a super case-II transport mechanism and followed first-order kinetics. Moreover, CL-AX-2 appeared to be a biocompatible and non-toxic material and hence highly suitable for sustained/targeted drug delivery.