pH responsive amoxicillin release from biopolymeric beads

Biopolymer-based bead hydrogels present promising systems for the controlled delivery of therapeutic agents, enabling prolonged and site-specific drug action. Alginate and pectin, naturally occurring polysaccharides extracted from plant sources, have been widely valued for their non-toxicity, gelling ability, and compatibility with biological environments. In this study, hydroxypropyl methylcellulose was incorporated into the pectin–alginate bead formulation to enhance structural integrity and regulate drug diffusion. The composite beads were ionically crosslinked with calcium or iron ions and characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Swelling behavior was investigated in simulated gastric and intestinal fluids to assess pH responsiveness. After 400 min, Ca²⁺ion crosslinked beads reached ∼60% swelling in simulated gastric fluid and ∼202% in simulated intestinal fluid, whereas Fe³⁺ion crosslinked beads reached ∼38% in simulated gastric fluid and ∼128% in simulated intestinal fluid, indicating that calcium-crosslinked systems swelled to a greater extent compared to their iron-crosslinked counterparts. Drug release studies further revealed that in simulated gastric fluid, Ca- and Fe-crosslinked beads exhibited cumulative amoxicillin releases of ∼15% and ∼11%, respectively, while in simulated intestinal fluid, the cumulative releases reached ∼90% and ∼75%. These results demonstrate that crosslinking density and polymer composition significantly affect both the release kinetics and the structural stability of the beads, supporting their potential use as pH-sensitive, biopolymer-based carriers in antimicrobial therapy.