Citric Acid-Mediated Crosslinking of Chia Seed Glucoxylan and Hydroxypropyl Cellulose: pH Responsiveness, Haemocompatibility and Sustained Drug Release.

The current study is focused on the synthesis of a novel stimuli-responsive bio-composite hydrogel as a pH-dependent sustained-release drug delivery system (DDS). The crosslinking of chia seed glucoxylan (GX) and hydroxypropyl cellulose (HPC) with citric acid (CA) was carried out using three different concentrations of CA, that is, 1%, 5% and 10% w/v. The FTIR spectroscopy, powder x-ray diffraction (PXRD), thermogravimetric analysis (TGA) and SEM analyses confirmed the successful formation of GX-HPC-CL-CA, amorphous nature, greater stability over native GX and porous structure, respectively. Among the three formulations, the GX-HPC-CL-CA-2 (prepared from 5% CA) offered the highest swelling capacity and followed by the pattern: deionized water (DW) > pH 7.4 > pH 6.8 > pH 1.2. The GX-HPC-CL-CA-2 and GX-HPC-CL-CA-2-based tablet possessed pH-responsive swelling, salt-responsive swelling and on/off switching (swelling-deswelling) behaviour at pH 7.4/1.2, in DW/normal saline and in DW/ethanol. The theophylline release was found to be 16.8%, 92.1% and 98.3% at pH 1.2, 6.8 and 7.4, respectively, after an 8 h study, indicating a pH-dependent release, followed the first-order kinetics and a non-Fickian diffusion mechanism. The GX-HPC-CL-CA-2 appeared to be a non-thrombogenic, non-haemolytic and non-toxic material, demonstrating a haemocompatible and pH-responsive bio-composite hydrogel for developing site-specific and sustained-release DDS.