Antimicrobial silver-hydroxyapatite composite coatings through two-stage electrochemical synthesis

• Nanoscale hydroxyapatite (HA) coatings were formed electrochemically on titanium.
• The HA coated titanium was then used for electrochemical reduction of silver.
• The two-stage coating method allows independent control of HA and silver properties.
• Resulting composite HA/silver nanoparticle coatings display antibacterial activity.
• The composite coatings also enhance biomineralization in vitro.

A two-stage electrochemical synthesis method was developed to prepare antimicrobial silver-hydroxyapatite (Ag-HA) composite coatings. In the first stage, a titanium substrate was coated with hydroxyapatite (HA) through electrochemical crystallization from aqueous solution. In the second stage, silver nanoparticles were deposited onto the HA layer through electrochemical reduction of aqueous Ag+ to Ag0. Silver nanoparticles having a narrow size distribution were found to deposit uniformly on the HA layer. The quantity and size of silver nanoparticles were shown to be controlled by the electrochemical deposition time under constant applied electrical current density. Ag-HA composite coatings were found to be bioactive based upon the promotion of the deposition of additional calcium phosphate onto the Ag-HA coating surface from simulated body fluid. Staphylococcus aureus bacteria growth was inhibited by coatings of Ag-HA, while HA coatings without silver had little effect on growth of the bacteria. The novel composite Ag-HA coatings can potentially be used in orthopedic and dental implants to simultaneously improve osseointegration and prevent post-surgical infection.