Influence of the electrolyte solutions on the physico-chemical properties and bioactivity of copper doped hydroxyapatite coatings

The present study investigates the properties of hydroxyapatite-based (HAp) coatings electrochemically obtained from two electrolytes of different nature and subsequently doped-with Cu, an element known for its antibacterial properties and ability to stimulate bone tissue regeneration. HAp coatings were deposited on titanium substrates under pulsed galvanostatic conditions at 75°C using calcium nitrate or calcium chlorate electrolytes, followed by Cu incorporation through an ion-exchange treatment in a copper-based solution. The resulting coatings were characterized in terms of morphology by scanning electron microscopy (SEM), while the chemical and phase composition were determined by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), respectively. Surface roughness and layer thickness were determined by surface profilometry. SEM images revealed that all coatings exhibited ribbon-like crystal morphologies, independent of electrolyte type or Cu addition. EDX confirmed the successful incorporation of Cu in the coatings and a (Ca+Cu)/P ratio between 1.54 and 1.58. The coatings obtained from chloride-based electrolytes were thinner than those obtained from nitrate-based ones, and Cu doping resulted in a slight decrease in thickness for both electrolyte systems. XRD analysis confirmed the presence of the HAp phase in all samples and verified successful Cu incorporation. In summary, hydroxyapatite coatings produced by electrochemical deposition method can be effectively doped with copper through an ion-exchange approach, offering potential for antibacterial and bone-regenerative applications.