Tailoring Biodegradation of Mg-Ca Alloy by Acid Pickling and Polydioxanone/n-Hydroxyapatite Composite Coating for Temporary Implant Applications

Magnesium (Mg) based alloys are good candidates for developing degradable metallic implants. Mg can easily degrade in a physiological environment without producing any toxic by-products. However, the degradation rate needs to be controlled to make it compatible with the tissue growth rate. Achieving enhanced degradation resistance and biological performance in the physiological environment without sacrificing its mechanical and physical properties has been a great challenge. In this work, a combination of surface pre-treatment and polymer nanocomposite coating is attempted for reducing degradation rate and improving biomineralization. The alloy surface was pickled in phosphoric acid and then coated with polydioxanone/hydroxyapatite nanocomposite. The samples were characterized using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). The corrosion resistance was studied using potentiodynamic polarization (PDP) test in 8.035 g/l NaCl solution. An immersion test in simulated body fluid (SBF) was also carried out to evaluate the biodegradation and biomineralization on the sample surfaces. Phosphoric acid pickling increased the corrosion resistance and adhesion between the coating and substrate. Polymer nanocomposite coating resulted in further control of degradation rate and enhanced biomineralization. Thus, pre-treated Mg-Ca alloys coated with polydioxanone/nHA composites can be considered as promising materials for developing degradable metallic implants.