Metallic orthopedic prosthesis is most commonly used due to its good mechanical properties, but its failure mostly occurs due to the lack of proper bone bonding and/or the occurrence of post-operative infections. Hydroxyapatite is commonly used as a bone filler biomaterial or as a coat for titanium prosthesis due to its decent biocompatibility, osseoconductivity, and bioactivity [26]. However, as a ceramic material, HA still has lower mechanical properties [27]. The biological apatite differs from synthetic apatite because the former contains numerous cationic substitutions, such as Zn²⁺, Na⁺, Mg²⁺, and has smaller size than synthetic apatite [28, 29]. It was proposed that the addition of zinc to hydroxyapatite had led to a reduction in inflammatory reaction and an improvement of bioactivity [28, 30].

Plasma spraying, sol-gel, and electrophoretic deposition has been all utilized to deposit HA on titanium implants, with some difficulties and worries of suppressing the HA particles’ adhesion, anodic polarization of metal substrate, and increasing metals’ corrosion risk [19,20,21]. Electrochemical deposition (ED) is the selected approach in this study due to its simplicity, easiness of parameters control, uniform coating thickness produced, and its applicability for multidimensional implant surfaces [22].

In the current study, an electrochemical deposition was applied to prepare nano-HA-Zn coating on titanium metal aiming to improve bioactivity, osseointegration, and preventing peri-implantitis. At this early point of research, the coatings’ procedure was accustomed to produce a uniform thickness of HA-Zn coating, characterize its chemical structure, observe its surface morphology, and evaluate the surface roughness and coat adhesive properties.

Recycling of natural-derived resources is a challenging task that may have both environmental and economical profits. Cuttlebone fishery is a naturally derived biomaterial that was used as a source of calcium during the electrochemical deposition process in this study. It was confirmed in the IR spectra (Fig. 2) that Ca(NO₃)₂·4H₂O resulted from the reaction of CaCO₃ of cuttlebone and nitric acid [31]. The selected time for electrochemical deposition of HA-Zn coating was 2 h; as by then, the formation of a white detectable coating had occurred and could be scrapped for IR spectral analysis. After preparation of HA-Zn coating, the analyzed powder appeared to still have the HA characterization. Li et al. prepared Zn-HA coatings through a hydrothermal method and found that the FT-IR spectra of Zn-HA has no significant changes than the as-prepared HA [32]; this Zn-HA spectrum paralleled with this study.