Volume 3, Issue 3 (March 2006)
Plasma Cleaning of a Commercially Available Hydroxyapatite-Coated External Fixation Pin by the Radio Frequency Glow Discharge Technique
The surface chemistry of a commercially available hydroxyapatite (HA)-coated external fixation pin in its as-received state has been studied using X-ray photoelectron spectroscopy (XPS). The XPS investigations revealed that the HA coating on the pin was contaminated with silicon (organosilicone) and it exhibited sub-stoichiometric chemical composition (i.e., Ca/P∼0.9). A comparison of the high resolution XPS spectra of both the HA-coated pin and the inside of its protective elastomer cap revealed that silicon to be in the form of an organosilane transferred from the protective cap to the HA surface, thus contaminating the latter. A parallel plate radio frequency glow discharge plasma cleaning system was successfully employed for removing the surface contaminant (organosilicone) from the HA-coated pin. As confirmed by XPS, plasma cleaning for 15 min was sufficient for achieving complete removal of the silicon contaminant and exposing a clean HA layer with a stoichiometric Ca/P ratio of 1.7.