Antibacterial properties of Ag (or Pt)‐containing calcium phosphate coatings formed by micro‐arc oxidation

Abstract

Silver (or platinum)-containing calcium phosphate (hydroxyapatite (HA) and tricalcium phosphate (alpha-TCP)) coatings on titanium substrates were formed by micro-arc oxidation (MAO) and their in vitro antibacterial activity and in vitro cytotoxicity were evaluated. MAO was performed in an electrolytic solution containing beta-glycerophosphate disodium salt pentahydrate (beta-GP) and calcium acetate monohydrate (CA), and Ag and Pt were introduced in the form of AgNO(3) (or CH(3)COOAg) and H(2)PtCl(6), respectively. The MG63 and human osteosarcoma (HOS) cell lines were used to investigate the proliferation and differentiation behavior of the cells, respectively, whereas two strains of bacteria, Staphylococcus aureus and Escherichia coli, were used to evaluate the antibacterial activity of the coatings. The phase, morphology, and Ag content of the coatings were strongly dependent on the applied voltage and Ag precursor concentration. HA and alpha-TCP phases were detected in the coatings oxidized above 400 V and the presence of Ag was confirmed by EDS. While the coatings with a high content of Ag were cytotoxic and those obtained in the Pt-containing electrolyte had no apparent antibacterial activity, the calcium phosphate coatings obtained in the low Ag concentration electrolyte exhibited in vitro antibacterial activity but no cytotoxicity. Thus, biocompatible calcium phosphate coatings on Ti implants with antibacterial activity can be achieved by one-step MAO.

Titanium Oxide Antibacterial Surfaces in Biomedical Devices

“…when anodization is carried out at higher voltages local melting and re-crystallization processes result in the incorporation of ionic species with a concentration gradient along the oxide: the electrolytic bath affects the final chemical composition of the grown oxide. An interesting treatment has been proposed by Song et al (88): they obtained Ag-or Pt-containing coatings on Ti-based implants by performing MAO in a bath composed of silver and platinum salts. Antibacterial properties were evaluated by using S. aureus and E. coli.…”

Review of Antibacterial Activity of Titanium-Based Implants’ Surfaces Fabricated by Micro-Arc Oxidation

“…Song et al [58] have incorporated Ag into Ti implants by MAO in 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP), 0.4 M CA and silver nitrate (AgNO 3 ) or silver acetate (CH 3 COOAg) electrolytic solution at a fixed applied voltage range from 250 to 450 V. The addition of AgNO 3 reduced the required voltage for the formation of calcium phosphate compounds from 450 down to 400 V [82,83]. When the concentration of AgNO 3 was fixed at 0.004 M, the oxidized layer was a porous microstructure with spherical pores at voltages below 350 V (Figure 5a), while the coating surface became rough and covered with spherical particles and flakes above 380 V (Figure 5b) due to the existence of calcium phosphate compounds (Figure 5c).…”

Nano-Ag-loaded hydroxyapatite coatings on titanium surfaces by electrochemical deposition

“…It also exhibits high thermal stability and low toxicity towards mammalian cells [18,19]. There are several methods to introduce Ag into Ca-P coatings, such as plasma spraying [20,21], ion beam-assisted deposition [22], magnetron sputtering [23], micro-arc oxidation [24] and sol -gel technology [25,26]. The first three methods are line-ofsight technologies and cannot be applied to the medical devices with a complex shape; the last two methods have the problem of controlling the distribution of Ag in the coatings.…”