In Vitro Bioactivity and Antibacterial Activity of Strontium-, Magnesium-, and Zinc-Multidoped Hydroxyapatite Porous Coatings Applied via Atmospheric Plasma Spraying

Abstract

The beneficial effects of Sr-and Mg-doped hydroxyapatite (HAp) on osteoblast proliferation and bone regeneration have been investigated in the past, and the antibacterial ability of Zn ions is well known. However, HAp coatings doped with these three elements via thermal spraying have not yet been investigated. In this study, HAp powder was synthesized at different pH values (4, 6, 8, and 10) and calcined at different temperatures (200, 400, 600, 800, and 1000 °C) to obtain HAp with the highest purity. Subsequently, strontium-, magnesium-, and zinc-doped HAp powders were synthesized at the optimal pH value and calcination temperature. The HAp powder was then coated onto Ti disks using atmospheric plasma spraying (APS) or vapor-induced pore-forming atmospheric plasma spraying (VIPF-APS) techniques at different working currents (350, 400, and 450 A) and spraying distances (10 and 15 cm). X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy equipped with energy-dispersive spectroscopy were used for material characterization to determine the optimal parameters. With these optimal coating parameters, HAp, Zn-HAp, SrMg-HAp, and ZnSrMg-HAp powders were deposited onto the Ti disks using VIPF-APS and named HAp-Ti, Zn-HAp-Ti, SrMg-HAp-Ti, and ZnSrMg-HAp-Ti, respectively. The in vitro bioactivity of these four groups was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and alkaline phosphatase (ALPase) activity assay. Besides, the antibacterial activities against Prevotella nigrescens, Porphyromonas gingivalis, and Fusobacterium nucleatum were assessed. The results showed that the purity of HAp synthesized at pH 10 and 800 °C was 98.40%. A porous coating without cracks was obtained at a 10 cm spraying distance and 400 A working current using VIPF-APS. SrMg-HAp-Ti and ZnSrMg-HAp-Ti resulted in higher osteoblast proliferation and ALPase activity than the control. Moreover, both Zn-HAp-Ti and ZnSrMg-HAp-Ti exhibited antibacterial activity against the three bacteria. Therefore, ZnSrMg-HAp has potential as a coating for biomedical materials due to its ability to reduce bacterial infection and enhance osseointegration.

Microstructural, electrical and biological activity in $$\mathrm{Ca}_{10}(\mathrm{PO}_4)_6(\mathrm{OH})_2-\mathrm{Ba}_{0.5}\mathrm{Sr}_{0.5}\mathrm{TiO}_3$$ ceramic composites designed for tissue engineering applications

“…In the case of the composites, the presence of Sr, Ba, Ti, and Ca are reported to delay the release of ions into SBF, which are later exchanged with in the solution 29 , 30 . The slow dissolution leads to continuous apatite nucleation on the interface of the discs.…”

“…In the composites containing , , , and , the biomineralization proceeds longer due to the additional ions. This reflects a higher ratio of the composites compared to the monoliths 29 , 30 . In the case of the monoliths that contain lesser positive ions, reflected lesser Ca/P ratio.…”

Enamel Remineralization and Dentine Tubules Occlusion by Bioactive Formulations Based on Ion-Doped Nanohydroxyapatite and Precursor Nanoparticles.

“…The content of Mg 2+ , Sr 2+ , Zn 2+ , and Fions in the whole products and water-insoluble fractions was determined usinginductively coupled plasma atomic emission spectrometer (ICP-OES) and ion-selective electrode (ISE) methods(Table 3). We have focused on these ions since, according to the literature, they are involved in remineralizing [28,29] and antibacterial activity [30,31]. The total uorine content of the products is in good agreement with the declared values of BT and BM(1450 ± 50 ppm) while it was a little low (about -20%) compared to the declared values of the reference (CT, 1450 ± 50 ppm) and MM (900 ± 50 ppm).…”

Nature-Inspired Unconventional Approaches to Develop 3D Bioceramic Scaffolds with Enhanced Regenerative Ability

“…Other cations frequently used as doping ions for hydroxyapatite are Zinc (ZnHA) and Silver ions (AgHA). Zinc revealed effects similar to strontium and often Sr 2+ and Zn 2+ ions are included in hydroxyapatite simultaneously to achieve synergistic effects [ 28 ]. Zinc ions promote the bone mineralisation processes by enhancing osteoblasts’ proliferation, cell growth, and differentiation while inhibiting the bone resorption by osteoclasts.…”