Physico-chemical behavior of magnesium-doped hydroxyapatite/chitosan composite layers in simulated physiological conditions.

In this manuscript we report the development of magnesium doped hydroxyapatite in chitosan matrix (5HMC_0, Ca10 -xMgx(PO4)6(OH)2, with xMg = 0.05) by adapted sol-gel method. Then, the 5HMC_0 composite layers were developed using dip-coating technique. The obtained composite layers were exposed to Dulbecco's Modified Eagle Medium (DMEM) for 7 and 14 days. Then, the 5HMC samples were thoroughly analyzed both before and after immersion in DMEM for 7 and 14 days in order to investigate the structural and compositional changes induced by the DMEM environment. To perform a comprehensive evaluation, multiple characterization techniques were used, including X‑ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). To investigate the chemical composition, bonding states, and surface characteristics of the 5HMC_0, 5HMC_7, and 5HMC_14 samples, X-ray photoelectron spectroscopy (XPS) analyses were performed. XPS provides detailed insight into the chemical transformations occurring at the composite surface. These methods provided detailed information on the surface morphology and chemical composition, of the 5HMC samples (before and after immersion in DMEM). FTIR analysis of 5HMC confirmed the presence of characteristic phosphate and amide bands at ∼1043 cm⁻¹ and ∼1650 cm⁻¹ , while AFM measurements revealed a surface roughness (Ra) of approximately 68.46 nm (for the 5HMC sample); SEM studies indicated a homogeneous, crack-free morphology (for the 5HMC sample), and XPS and EDS analysis showed the Mg incorporation in the 5HMC composite layers. The biological properties of 5HMC layers were evaluated before and after immersion in DMEM medium with the aid of HGF-1 cell line (ATCC CRL-2014). The cell viability assay MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) showed that the 5HMC layers supported the proliferation of the fibroblast cells on their surface (having a cell viability above 94%). More than that, this preliminary study highlights the importance of 5HMC layers, demonstrating their favorable physicochemical and biological characteristics after exposure to DMEM, supporting their potential suitability for applications in bone implants, as well as in the orthopedic and dental fields.