A Smart Hydrogel from Salvia spinosa Seeds: pH Responsiveness, On-off Switching, Sustained Drug Release, and Transit Detection

Background: The use of synthetic and semi-synthetic materials in drug delivery systems has associated drawbacks like costly synthesis, toxicity, and biocompatibility issues. Therefore, there is a need to introduce novel materials to overcome such issues. Naturally occurring and water-swellable polysaccharides are advantageous in overcoming the above-mentioned issues. Therefore, we are reporting a novel hydrogel (SSH) isolated from the seeds of Salvia spinosa as a sustained release material. Methods: SSH was explored for its pH-dependent and salt-responsive swelling before and after compression in a tablet form. Stimuli-responsive swelling and deswelling were also monitored at pH 7.4 and pH 1.2 in deionized water (DW) and normal saline and DW and ethanol. The sustained-release potential of SSH-based tablets was monitored at gastrointestinal tract (GIT) pH. The transit of SSH tablets was ascertained through an X-ray study. Results: The swelling of SSH in powder and tablet form was found in the order of DW > pH 7.4 > pH 6.8 > pH 1.2. An inverse relation was found between the swelling of SSH and the concentration of the salt solution. The SSH showed stimuli-responsive swelling and de-swelling before and after compression, indicating the unaltered nature of SSH even in a closely packed form, i.e., tablets. Sustained release of theophylline (< 80%) was witnessed at pH 6.8 and 7.4 during the 12 h study following zeroorder kinetics, and radiographic images also showed 9 h retention in GIT. Conclusion: These investigations showed the potential of SSH as a pH-sensitive material for sustained and targeted drug delivery.