Noble metals role in autocatalytic phosphate coatings on TAV alloys. I.Ag functionalization of autocatalytic phosphate deposition on TAV alloys

• Two smart and facile chemical routes were developed for coating Ti6Al4V (TAV) metallic implants with calcium phosphate.
• Ag inclusion in the baths instead of Pd imparted dual function of enhancing the reactions and as a bactericidal agent.
• Metallic substrates coated through alkaline bath are recommended for orthopedic application.
• Acidic baths are more suitable for dental applications benefiting the presence of fluoride in the mother media.
• Ag functionalized phosphatic layers are expected to enhance mutual surgical site compatibility and interlocking at interface.

The autocatalytic route was created using AgCl similar to PdCl2 to develop calcium phosphate layer on Ti6Al4V (TAV) substrates as previously demonstrated by the present authors. Alkaline (NaOH)-treatment and heat regimes were performed to render the surfaces susceptible to deposition. The anti-bacterial test was achieved for the treated substrates. Further, they were immersed in simulated body fluid (SBF) up to seven days to assess the biochemical stability of deposited coats. Biochemical analyses were performed for SBF left post three and seven days of immersion to evaluate calcium and phosphorus contents. The corresponding formed layers were compared using FESEM, confocal microscopy, TEM and TFXRD, pre- and post-SBF immersion. Results proved that the autocatalytic baths were successful in precipitating Ca–P coatings on the pre-treated substrates after only 2 hours immersion possessing clear inhibition zones of Escherichia coli B210 demonstrating their antibacterial function. A globular phosphatic layer was achieved one-week post immersion in comparison to that of Kokubo's which needed 10–30 days. The presence of Ag should have promoted the phosphate formation by reducing its oxidation potential post-SBF immersion.