In vitro antibacterial evaluation of sol–gel‐derived Zn‐, Ag‐, and (Zn + Ag)‐doped hydroxyapatite coatings against methicillin‐resistant Staphylococcus aureus

Abstract

Hydroxyapatite (HAp) coatings were applied using sol-gel method. Phosphor pentoxide and calcium nitrate were used as phosphorous and calcium precursors, respectively. Zinc nitrate and silver nitrate were used as substitute of calcium in HAp structure. As a base concentration, 1.5 wt %Ag and 2.5 wt %Zn were used. The weight percent of Ag was increased at 0.3 wt% and Zn content was scaled down at 0.5 wt%. Phase analysis and chemical bonds of synthesized materials were studied by XRD and FTIR. Antibacterial activity of Ag- and Zn-doped samples against methicilin-resistant Staphylococcus aureus (MRSA) were assessed by the plate-counting method. The XRD and FTIR results proved formation of HAp compound. Colony counting showed that silver and zinc ions prevent proliferation and growth of MRSA. Interestingly, co-presence of metal ions improves the antibacterial effectiveness of the coatings and the combined effect was greater than sum of the individual effects when each was administered alone. Overall, synergism between antibacterial activities of Zn(2+) and Ag(+) ions against MRSA can be suggested. Thus, cell toxicity decreases and biocompatibility increases without any decrement in antibacterial activity.

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].…”

“…Finally very few single or colonized bacteria adhered on the 6 wt% Ag-doped HAp (HAp/6Ag) coatings, and among them, live bacteria were very limited (Fig. 4b, d) Two possible underlying mechanisms for the antibacterial action of Ag-HAp have been proposed [178-180, 183, 209, 210]: (i) the direct interaction between the bacterial cell membrane and silver ions due to an attraction of the microorganisms towards the surface of the hydroxyapatite by electrostatic forces and (ii) the bactericidal activity of the slowly released silver ions from the hydroxyapatite [181,209]. In both cases, cell death occurs as a consequence of remarkable and significant morphological changes, as supported by AFM investigation [161].…”

Biocompatibility and Anti-Bacterial Activity of Zn-Containing HA/TiO2 Hybrid Coatings on Ti Substrate

“…Researches confirmed that the calcium phosphate ceramic coatings containing zinc promoted biological activity of osteoblasts than the pure HA coating in vitro 7) . It can also be used as antimicrobial elements, and showed good anti-bacterial activity 8). …”

Silver nanoparticles and their orthopaedic applications

“…These include ion exchange, thermal decomposition, sol-gel technology, magnetron sputtering, ion beamassisted deposition and electrochemical deposition. [46][47][48][49][50] The goal is to achieve a uniform coating that produces an antibacterial effect without compromising the osteoconductive effect of HA. The results have been promising, with most studies concluding that silver can be added to HA coatings without affecting the mechanical properties of HA.…”