The Study of Nanosized Silicate-Substituted Hydroxyapatites Co-Doped with Sr²⁺ and Zn²⁺ Ions Related to Their Influence on Biological Activities

Abstract

Nanosized silicate-substituted hydroxyapatites, characterized by the general formula Ca9.8−x−nSrnZnx(PO4)6−y(SiO4)y(OH)2 (where: n = 0.2 [mol%]; x = 0.5–3.5 [mol%]; y = 4–5 [mol%]), co-doped with Zn2+ and Sr2+ ions, were synthesized with the help of a microwave-assisted hydrothermal technique. The structural properties were determined using XRD (X-ray powder diffraction) and Fourier-transformed infrared spectroscopy (FT-IR). The morphology, size and shape of biomaterials were detected using scanning electron microscopy techniques (SEM). The reference strains of Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa were used to assess bacterial survivability and the impact on biofilm formation in the presence of nanosilicate-substituted strontium-hydroxyapatites. Safety evaluation was also performed using the standard cytotoxicity test (MTT) and hemolysis assay. Moreover, the mutagenic potential of the materials was assessed (Ames test). The obtained results suggest the dose-dependent antibacterial activity of nanomaterials, especially observed for samples doped with 3.5 mol% Zn2+ ions. Moreover, the modification with five SiO4 groups enhanced the antibacterial effect; however, a rise in the toxicity was observed as well. No harmful activity was detected in the hemolysis assay as well as in the mutagenic assay (Ames test).

Keywords

• nanosilicate-substituted hydroxyapatite
• Sr²⁺ and Zn²⁺ doping
• antibacterial activity
• antibiofilm activity
• cytotoxicity