Electrodeposition of Brushite Coatings and Their Transformation to Hydroxyapatite in Aqueous Solutions

In this study we examine the potential for using brushite (dicalcium phosphate dihydrate) as a coating for orthopedic implants. It was found that brushite is transformed into a more stable calcium phosphate (hydroxyapatite), regardless of the aqueous transforming media utilized. The transformation was carried out at room temperature in deionized water, deionized water with added calcium ions, and modified Hank's type solution without calcium and magnesium ions, modified Hank's type solution with calcium and magnesium ions, and modified Hank's type solution with added calcium ions. In several of the transformation systems it was noted that brushite provided an increased amount of calcium ions to the transforming media through solubility. The process was monitored using X-ray diffraction, X-ray photoelectron spectroscopy, and dissolution studies. Scanning electron microscopy and energy dispersive spectroscopy were also utilized for characterization. The brushite coatings can be easily achieved electrolytically on conducting substrates. The process is non line of sight, simple, and inexpensive; and when using an electrolyte that can sustain currents of approximately 100 mA/cm2, the necessary coating can be completed in about 3 min.