pH-Driven Structural Optimization of Hydroxyapatite/Alginate Composites for Sustained Clindamycin Release and Antibacterial Applications

Abstract

Bacterial infections, especially those caused by Staphylococcus aureus and Escherichia coli, still pose a significant challenge for biomedical applications, such as the management of wound and bone infections. This investigation aimed to prepare and characterize hydroxyapatite–alginate (HAp/Alg) composites from bamboo shell waste at several synthesis pHs (7–10) and to study their potential as clindamycin-loaded antibacterial drug delivery systems. XRD results showed that hydroxyapatite was the main crystalline phase in all samples, while FTIR analysis confirmed the presence of both hydroxyapatite and alginate in the composite. As a result, the smallest crystallite size of HAp/Alg-10 (21.25 nm) among the composites that were investigated was considered for an in-depth characterization. The average particle size of the sub-micron particles observed through SEM analysis was around 669 nm, while elemental analysis using EDS revealed that Ca, P, O, and C were the major elemental constituents, along with a Ca/P atomic ratio of 2.15. Release profile characteristics (for clindamycin-loaded HAp/Alg composite) showed an initial burst release followed by a slower sustained-release stage, collecting to 69% cumulative release after 8 h. Antibacterial tests indicated that S. aureus-biotic treatment produced inhibition zones of 7 mm and E. coli zone diameters of 4 mm (>1–2 mm for cells not treated with biotics from the unloaded HAp/Alg composite). These outcomes also imply that clindamycin was efficiently carried on the composite matrix and released in a sustained manner. In conclusion, the bamboo shell-derived HAp/Alg composite produced at pH 10 was a potential candidate for localized antibacterial drug delivery systems in biomedical applications