A comprehensive investigation of strontium doped hydroxyapatite-merwinite composite: In-vitro biomineralization, mechanical testing, and cytotoxicity analysis

The advancement of biomaterials for reconstruction and replacement of damaged tissues is essential, which would possess biocompatibility, better mechanical, biochemical, and physical properties. Merwinite (Ca3MgSi2O8) has emerged as a promising material for hard tissue engineering, particularly in composite with hydroxyapatite (HAp). Strontium-doped hydroxyapatite (SrHAp) was prepared with varying dopant concentrations (1%, 3%, and 5% Sr) on the calcium site of HAp. The materials were analyzed by XRD, FTIR and SEM/EDX techniques. XRD analysis revealed average crystallite sizes ranging from 46 to 50 nm for SrHAp. It was found that the Merwinite-SrHAp composite doped with 5% strontium had a higher rate of apatite nucleation compared to pure composite, indicating that strontium doping enhances the bioactivity of the composite. The composite scaffolds, prepared in an 80:20 ratio of SrHAp to merwinite, exhibited compressive strengths ranging from 63.43 MPa (1% Sr doping) to 80.68 MPa (5% Sr doping). Cytotoxicity assessment against MG63 cell line via MTT assay demonstrated cell inhibition rates ranging from 11.71% (at 6.5 μg/mL) to 68.35% (at 100 μg/mL) for the 5% Sr-doped composite. Alkaline phosphatase (ALP) investigation revealed enhanced ALP activity for cells cultured on the 5% Sr-doped composite compared to control samples, indicating increased cell differentiation and mineralization potential.