Bentonite increases the corneal permeation of the drug from the tamarind gum hydrogels

Abstract Tamarind gum (TG) polysaccharide is used as a viscosity-modifying agent in the pharmaceutical, textile, and food industries. In this study, we prepared TG-bentonite-based composite hydrogels as ocular drug-delivery systems. The hydrogels were thoroughly characterized using various techniques such as microscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, mechanical testing, and impedance spectroscopy. The microstructure of the hydrogels demonstrated the presence of globular structures due to the aggregation of the xyloglucan residues in the hydrogel matrix. FTIR analysis revealed that the extent of intermolecular hydrogen bonding varied within the hydrogels as the composition was tailored. The hydrogel containing the highest amount of bentonite exhibited the most mechanically stable architecture. The thermograms demonstrated that the concentration of bentonite dictated interactions among the hydrogel components. The hydrogels showed a gradual decrease in the resistive component with an increment in the bentonite proportion. The presence of bentonite decreased the in vitro release of the model drug (Ciprofloxacin HCl) molecules from the hydrogels. However, the transcorneal permeation of the model drug increased with the corresponding increase in the bentonite proportion. Draize eye test confirmed the nonirritant nature of the prepared hydrogel formulations. Drug-loaded hydrogels also showed good antimicrobial efficacy against the model organisms Escherichia coli and Bacillus subtilis.