Tunable agar/carrageenan-bentonite hybrid films for pH-responsive gentamicin delivery

Novel agar-carrageenan-bentonite hybrid biocomposite films were engineered as tunable platforms for pH-responsive gentamicin delivery. Natural polysaccharide, polysaccharide-bentonite, and drug-loaded biocomposite films were prepared by an eco-friendly solvent-casting method. Structural, thermal, and physicochemical properties were investigated using XRD, ATR-FTIR, UV-vis, TGA, and DTA. The results confirmed gentamicin intercalation within bentonite interlayers, partial clay exfoliation, and improved polymer-clay interactions, enhancing thermal stability while preserving drug integrity. Antibacterial efficacy was evaluated against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). In vitro swelling studies demonstrated rapid water uptake during the first hour of immersion. At pH 2.1 and pH 7.4, swelling depended on the agar/carrageenan ratio, reaching approximately 12 g/g after about 4 h. Release studies showed pH-dependent gentamicin release. The optimized FBP5 formulation achieved near-complete drug release (99.99%) within 24 h while maintaining potent antibacterial activity against S. aureus. This performance is attributed to the synergistic interplay between bentonite’s ion-exchange capacity, agar’s structural scaffolding, and carrageenan’s pH-sensitive swelling properties.