Freeze-dried magnesium doped hydroxyapatite for biomedical applications

The present study, presents for the first time the development and characterization of innovative bioceramic samples based on magnesium doped hydroxyapatite (x_Mg = 0.015 and x_Mg = 0.05) obtained by a modified co-precipitation method and the lyophilization of the final precipitate (1.5MgHAp-LF and 5MgHAp-LF). The lyophilized powders were thoroughly investigated, obtaining valuable information regarding stability through non-destructive ultrasound measurements, structure, chemical composition, bonding states, surface properties and biological evaluations. The X-ray diffraction (XRD) patterns of the samples revealed peaks characteristic of pure hexagonal hydroxyapatite (P63/m). When calcium ions were substituted with magnesium ions, a reduction in peak intensity and a slight broadening of the peaks were observed as the magnesium concentration increased. Fourier transform infrared spectroscopy (FTIR) was used to investigate the structural and compositional characteristics of the studied samples. Information regarding the surface topography of 1.5MgHAp-LF and 5MgHAp-LF pellets was obtained using scanning electron microcopy (SEM) and atomic force microscopy (AFM) studies. Additionally, AFM topographies and SEM images provided useful insights into the roughness of the samples. A complementary analysis was performed on a larger surface area using a Scanning Acoustic Microscope (SAM). The biological performance of 1.5MgHAp-LF and 5MgHAp-LF pellets was evaluated using the MG63 osteoblast-like cell line. Surface analyses-including furrow morphology, texture orientation, fractal dimensionality, and frequency spectrum-revealed that increased magnesium content induces greater topographical order and complexity, enhancing the material's potential for osteoconductive applications. The cytotoxicity of the pellets was assessed by determining the cell viability through the MTT assay after an incubation period of 24 h. Also, fluorescence microscopy (FM) visualization was used to determine the cytotoxicity of the pellets. The results demonstrated that both 1.5MgHApLF and 5MgHApLF pellets exhibited good biocompatibility for both tested samples. Furthermore, the interaction of the MG63 cells with the surface of the 1.5MgHAp-LF and 5MgHAp-LF pellets was assessed by metallographic microscopy (MM) and atomic force microscopy (AFM). MM and AFM analyses revealed that the surface morphology of both materials effectively supported cellular attachment and growth. These findings suggest that both 1.5MgHAp-LF and 5MgHAp-LF pellets have a significant potential for being used in the development of advanced biomaterials for biomedical use.