Antibacterial and biological characteristics of silver containing and strontium doped plasma sprayed hydroxyapatite coatings

Abstract

Infection in primary total joint prostheses is estimated to occur in up to 3% of all surgeries. As a measure to improve the antimicrobial properties of implant materials, silver (Ag) was incorporated into plasma sprayed hydroxyapatite (HA) coatings. To offset potential cytotoxic effects of Ag in the coatings, strontium (Sr) was also added as a binary dopant. HA powder were doped with 2.0 wt% Ag2O, 1.0 wt% SrO and the powder was then heat treated at 800° C. Titanium substrates were coated using a 30 kW plasma spray system equipped with a supersonic nozzle. X-ray diffraction (XRD) confirmed the phase purity and high crystallinity of the coatings. Samples were evaluated for mechanical stability by adhesive bond strength testing. Results show that the addition of dopants did not affect the overall bond strength of the coatings. The antibacterial efficacies of the coatings were tested against Pseudomonas aeruginosa. Samples that contained the Ag2O dopant were found to be highly effective against the bacterial colonization. In vitro cell-material interactions using human fetal osteoblast (hFOB) cells were characterized by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cell viability, field emission scanning electron microscopy (FESEM) for cell morphology and confocal imaging for the important differentiation marker alkaline phosphatase (ALP). Our results showed evidence of cytotoxic effects in the Ag-HA coatings, characterized by poor cellular morphology and cell death and nearly complete impediment of functional ALP activity. The addition of SrO to Ag-HA coatings was able to effectively offset these negative effects and improve the performance when compared to pure HA coated samples.

Cationic and Anionic Substitutions in Hydroxyapatite

“…The produced systems include the co-substitution of zinc/silver [209], silver/strontium [211], carbonate/strontium [492], carbonate/magnesium [454,493], carbonate/sodium [494], carbonate/silicate [495], yttrium/silicon [496], zinc/silicate [497], zinc/copper [498], strontium/cerium [499], magnesium/ strontium [500], magnesium/silver [501], and carbonate/silicate/magnesium [454]. However, the co-substitution of multiple (more than two) ions has not deeply and systematically attempted and investigated, and thus, it can be considered as a promising research field to be still and further explored and expanded [502,480].…”

“…On the basis of in vitro studies on human stem cells, it was possible to conclude that HAp containing 0.3 wt% Ag does not play negative action on cell growth up to 7 days of culture, whereas 0.7 wt% Ag slightly inhibits their growth and 8.3 wt% Ag plays a remarkable cytotoxic effect, specifically in the case of human stem cells [190]. Concerning the in vitro experiments on human osteoblasts, Ag amounts of 2 wt% and 4 wt% represent a good balance and compromise between effective antimicrobial and cytotoxic activity [208,211] (Fig. 4), while Ag content of 6 wt% significantly inhibits osteoblast growth, sometimes causing their death [208].…”

“…Additionally, in vitro toxicity studies on human osteoblasts [207,208,211,212], human stem cells [190], and mouse fibroblasts [213] were carried out. On the basis of in vitro studies on human stem cells, it was possible to conclude that HAp containing 0.3 wt% Ag does not play negative action on cell growth up to 7 days of culture, whereas 0.7 wt% Ag slightly inhibits their growth and 8.3 wt% Ag plays a remarkable cytotoxic effect, specifically in the case of human stem cells [190].…”

Antibacterial activity and biological performance of a novel antibacterial coating containing a halogenated furanone compound loaded poly(L-lactic acid) nanoparticles on microarc-oxidized titanium

“…25 Considering the susceptibility of the implant surface to bacterial adhesion, which may cause implantassociated infection, antibacterial coatings have been traditionally designed to prevent the initial bacterial adhesion. 26 Long-term antibacterial ability is especially significant for implants because of the constant risk of bacterial infection.…”

Antibacterial Properties and Corrosion Resistance of the Newly Developed Biomaterial, Ti–12Nb–1Ag Alloy

“…However, these materials and methods were largely unsuccessful. Therefore, in the current study, we homogenized the materials using the melting method to ensure homogeneous and persistent dissolution of the metal ions in order to achieve enduring efficacy [38,39].…”