Effect of copper (Cu2+) inclusion on the bioactivity and antibacterial behavior of calcium silicate coatings on titanium metal.

The present study is an investigation of the effect of copper (Cu2+) inclusion on the bioactivity, antibacterial behavior, corrosion resistivity and leaching characteristics of calcium silicate coatings on titanium metal. The synthesis of stoichiometric CaSiO3 and five different concentrations of Cu2+ substitutions in CaSiO3 was carried out. The incorporation of Cu2+ in the crystal lattice of CaSiO3 was investigated by means of the Rietveld refinement technique. The results from the structural investigation have shown that stoichiometric CaSiO3 crystallizes in the monoclinic system (space group = P121/a1 and unit cell parameters a = 15.4241 (5) Å, b = 7.3276 (7) Å and c = 7.0620 (8) Å with α = 90°, β = 95.404° and γ = 90°) and are in good agreement with the literature data for crystalline CaSiO3. The substitution limit of Cu2+ in the crystal lattice of CaSiO3 was determined as 4.399 wt% of Cu2+ and the increased level of Cu2+ substitution resulted in the formation of an additional phase in the form of tenorite (CuO). The fabrication of stoichiometric CaSiO3 and Cu2+ substitutions in CaSiO3 coatings on Ti metal was achieved through an electrophoretic deposition technique and no change in the phase behavior of the coatings was noted until the heat treatment temperature reached 800 °C. Immersion tests of CaSiO3 coatings in simulated body fluid solution resulted in the formation of an apatite layer within 3 days of immersion. Antibacterial tests showed that pure CaSiO3 powders did not exhibited any antibacterial activity whereas the presence of Cu2+ in CaSiO3 resulted in good activity against E. coli and S. aureus. Potentiodynamic polarization tests performed on the Cu2+ doped CaSiO3 coatings resulted in its better corrosion resistivity when compared to the pure metal and dissolution tests performed on coatings resulted in the leaching of Cu2+ at low levels.