A Study of Zeta Potential of Plasma Sprayed Hydroxyapatite Coating in Four Simulated Physiological Solutions

The zeta potential magnitude and the duration of its changes have been thought to be directly related to the surface reactivity, the governing of osteoconductivity and availability of valuable information in determining the anticipated in-vivo performance of implants. In this study the zeta potential of plasma sprayed hydroxyapatite (HA) was evaluated in various simulated physiological solutions. For this purpose the prepared samples were immersed in SBF, Ringers, Tyrodes and Hanks solutions for 3 weeks and kept at 37°C and the time dependent variations of zeta potential results were compared with calcined (2 hr at 850°C) and as-precipitated HA powders. Furthermore, following immersion test, the coating surfaces were examined with SEM and XRD as well as FTIR methods. The results showed that in majority of solutions, the zeta potential increased in the following order: calcined, as precipitated and plasma sprayed. Moreover, the ion concentrations and types in the solutions have significant effects on the zeta potential values. Following the immersion test, the morphology of the samples were determined a function of the thermal history of HA, duration of immersion and the type of the test solution. The results indicated that the surface of the HA coated samples were unstable with significant changes in the observed charge.