Synthesis, characterization, and acute toxicity of pH-responsive Salvia spinosa mucilage-co-acrylic acid hydrogel: A smart excipient for drug release applications

Owing to the increasing demand for pH-responsive excipients based on natural polysaccharides, a copolymeric biocomposite material was developed for sustained release drug delivery system (DDS). A novel pH-responsive, non-toxic, and superabsorbent graft copolymeric hydrogel (SSH-co-AA) based on mucilage from Salvia spinosa seeds (SSH) and acrylic acid (AA; monomer) was fabricated through free radical copolymerization using N,N '- methylene-bis-acrylamide (MBA; cross-linker) and potassium persulfate (KPS; initiator). The Fourier transform infrared and CP/MAS 13C-NMR solid-state NMR spectroscopic analyses confirmed the successful grafting of AA onto SSH. The Powder X-ray diffraction analysis indicated the complete entrapment of crystalline drug in the amorphous polymeric network. Newly fabricated hydrogel is thermally more stable than SSH as revealed through thermogravimetric analysis (TGA). The scanning electron microscopic images indicated the porous nature of SSH-co-AA. An increase in the gel fraction is observed by increasing the concentration of SSH, AA, and MBA. The porosity of SSH-co-AA is directly proportional to the concentration of SSH and AA and inversely proportional to the concentration of MBA. The swelling of SSH-co-AA followed second-order kinetics and the sustained release of venlafaxine HCl followed the Korsmeyer-Peppas model and non-fickian diffusion mechanism. Acute oral toxicity studies of SSH-co-AA reported non-toxic and non-irritant attributes.