Development of a hydroxyapatite coating containing silver for the prevention of peri-prosthetic infection

We hypothesized that the electrochemical deposition of hydroxyapatite (EHA) can be used to incorporate silver (Ag), providing a controlled and sustained release of Ag ions at a bactericidal concentration. Six groups were investigated: electrochemical co-precipitation of HA and Ag (EHA/Ag); EHA pre-coated discs treated in AgN0(3) (EHA/AgN0(3)); plasma sprayed HA (PHA) pre-coated discs treated in AgN0(3) (PHA/AgN0(3)); EHA with 2 "layers" of Ag (EHA/Ag/2 layers); EHA coating only; and PHA coating only. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses quantified coating thickness, calcium/phosphorous ratio, and % atomic silver content, respectively. Inductively coupled plasma-mass spectrometry quantified the amount of Ag released in phosphate-buffered saline, and zone of inhibition tests on agar plates using a lawn of Staph aureus were quantified in each group. XRD and EDX analysis confirmed the presence of Ag in all coatings. EHA coated discs with two layers of Ag and the EHA discs soaked in AgN0(3) showed significantly higher zones of inhibition at all time points when compared with all other groups (except PHA/AgN0(3) on day 0). This study demonstrated that Ag ions can be incorporated into a HA coating using an electrochemical technique.