The effect of antibacterial ingredients and coating microstructure on the antibacterial properties of plasma sprayed hydroxyapatite coatings

In this work, three kinds of antibacterial ingredients were loaded into the hydroxyapatite (HA) coating: antibiotic (ampicillin sodium salt), silver ions and water soluble chitosan. Two different kinds of HA coatings with dense and porous structures were prepared by the air plasma spraying (APS) and liquid precursor plasma spraying (LPPS) processes, respectively, for loading the antibacterial ingredients. The effects of different antibacterial ingredients and different coating microstructures on the antibacterial behaviors of HA coatings have been systematically studied. The antibiotic loaded HA coatings showed the best antibacterial activity, while the silver ion loaded HA coatings showed the worst bacterial inhibitory effects among the three kinds of antibacterial materials. The LPPS porous coating loaded with chitosan demonstrated the same excellent antibacterial effect as the antibiotic loaded coatings, while the APS dense coatings loaded with chitosan showed almost no antibacterial effect at 24 h. Overall, the HA coating with porous structure showed increased loading of antibacterial materials and enhanced antibacterial properties. Such observations suggest that both antibacterial material and coating structure have strong influences on the antibacterial properties of the HA coatings.