A chia (Salvia hispanica L.) seed mucilage-based glucoxylan-grafted-acrylic acid hydrogel: a smart material for pH-responsive drug delivery systems

The present research study is based on the extraction of the chia seed mucilage (CSM) composed of a polysaccharide (glucoxylan). The CSM and acidic monomer acrylic acid (AA) are used to synthesize a copolymer hydrogel, i.e., CSM-grafted-polyacrylic acid (CSM-g-PAA), as a novel pH-dependent sustained release drug delivery system (DDS). Fourier transform infrared (FTIR) spectroscopy and solid-state cross-polarization magic angle spinning nuclear magnetic resonance (CP/MAS ¹³C NMR) spectroscopy analyses confirmed the formation of CSM-g-PAA through the graft copolymerization of the CSM with AA. Scanning electron microscopy (SEM) images demonstrated the porous surface of CSM-g-PAA. The swelling capacity (g g⁻¹) of CSM-g-PAA and drug (nicorandil) release (%) from nicorandil-loaded CSM-g-PAA (Nic-CSM-g-PAA) were found to be dependent on the pH of the dissolution medium and the concentrations of CSM, AA, and the crosslinker N,N-methylene-bis-acrylamide (MBA). The gel fraction (%) in CSM-g-PAA was increased upon increasing the concentrations of CSM, AA, and MBA. The porosity (%) of CSM-g-PAA was increased with the increase of CSM and AA concentrations and decreased with increasing MBA concentration. The drug was loaded onto CSM-g-PAA and the amount of nicorandil loaded onto CSM-g-PAA (mg g⁻¹) was determined by a gravimetric method. The loading amount of nicorandil onto CSM-g-PAA was found to be directly dependent on the swelling capacity of CSM-g-PAA. The swelling of CSM-g-PAA followed second-order kinetics, whereas nicorandil release at pH 6.8 and 7.4 from Nic-CSM-g-PAA followed first-order-kinetics. The mechanism of nicorandil release from Nic-CSM-g-PAA was non-Fickian transport. Conclusively, CSM-g-PAA could be an efficient vehicle for the targeted administration of nicorandil to the small intestine.