Efficient destruction of bacteria with Ti(IV) and antibacterial ions in co-substituted hydroxyapatite films

Hydroxyapatite (Ca10(PO4)6(OH)2: HAP) was co-substituted with Ti(IV) and antibacterial ions (Ag+, Cu2+ or Zn2+) (HAPTiM), by coprecipitation and ion-exchange methods. Both HAPTiAg and HAPTiCu coated on porous spumous nickel film showed high efficiency for killing Escherichia coli and Staphylococcus aureus in the dark and under weak UVA irradiation, respectively. Moreover, their bactericidal activities were much higher than that of P25-TiO2 film. The studies of ESR revealed that not only O2− was formed on HAPTiM, HAPTi, HAP and P25-TiO2 films under weak UVA irradiation, but also at ambient temperature without light O2− was generated on HAPTiCu, HAPTiAg, and HAPTi. The redox couples of Cu0/Cu2+ and Ag0/Ag+ in the structure of HAPTiCu (Ag) caused the transfer of electron leading to the O2− generation under the above conditions. The higher bactericidal activities of HAPTiM were due to the synergy of the oxidation role of the O2− and the bacteriostatic action of antibacterial ions. The process of the damage of the cell wall and the cell membrane was directly observed by TEM, and further confirmed by the determination of potassium ion (K+) leakage from the killed bacteria.