Synthesis, characterization, and antimicrobial properties of hydroxyapatite/montmorillonite composite enriched with strontium

This study explores the development of a novel composite material based on hydroxyapatite (HAP) and strontium-modified montmorillonite (Sr-MMT) for potential use in bone tissue engineering. HAP/Sr-MMT composites were synthesized in-situ via co-precipitation method with a Ca/P molar ratio of 1.67 and different percentages of SrMMT (1, 5, 10, 20, 30wt.%). The physicochemical properties of these composites were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The antimicrobial activity of the materials was also evaluated. XRD results confirmed the presence of apatite and clay mineral phases, and showed, after calcination, the decomposition of the HAP structure and the formation of secondary phases (beta and alpha-Ca3(PO4)2) at high Sr-MMT content. FT-IR analysis confirmed the existence of surface interactions between the apatitic structure and the modified clay. SEM observations show a relative influence of Sr-MMT on composite morphology, with a more compact microstructure when the clay phase is added. Antimicrobial tests demonstrated enhanced activity against tested bacterial and fungal strains, particularly for composites with low Sr-MMT content. The HAP-1SrMMT exhibited the lowest of MIC and MBC/MFC values against all the bacterial and fungal strains used as targets. The sample loaded with 1 wt% Sr-MMT had an excellent activity against all the tested bacterial and fungal strains, as indicated by the lowest minimal inhibition concentration values of 16.66-33.33 mg/mL, 4.16- 8.33 mg/mL, respectively. These findings suggest the potential of the novel obtained HAP/Sr-MMT composites as promising biomaterials with enhanced biological and antimicrobial properties for bone tissue engineering applications.