## 1 Introduction  
Titanium alloys, particularly Ti-6 Al-4V, have been extensively used in biomedical applications such as orthopedic implants, dental prosthetics, and cardiovascular devicesdue to their high mechanical strength, low density, excellent corrosion resistance, and superior biocompatibility [1; 2; 3; 4]. Due to these attributes, Ti-6 Al-4V is widely chosen for long-term in vivo applications that demand mechanical reliability and biological safety [2]. Ti-6 Al-4V is classified as an \(\alpha+\beta\) titanium alloy, offering a balance of strength, ductility, and thermal stability [2; 3; 4]. Its biocompatibility is primarily attributed to the spontaneous formation of a passive titanium dioxide (TiO\({}_{2}\)) layer, which acts as a protective barrier against corrosion and reduces metal ion release. This oxide layer regenerates rapidly when damaged and promotes osseointegration, thereby improving implant stability over time [2]. Despite its advantages, Ti-6 Al-4V also presents several limitations. It is expensive to produce and difficult to machine due to its high hardness. Additionally, it is prone to wear under certain mechanical conditions and exhibits poor thermal conductivity. Another concern is its tendency toward biofilm development, which can undermine the long-term performance of biomedical implants [2; 4]. These drawbacks have led to the development of surface modification strategies to improve the alloy's biological and mechanical performance. A frequently used strategy consists of generating a TiO\({}_{2}\) layer through anodization or thermal oxidation. [PERSON] et al. [5] demonstrated that modifying the Ti-6 Al-4V surface with a nanoporous TiO\({}_{2}\) layer significantly improved the physicochemical properties and osseointegration potential of the substrate. This layer improves wear resistance and energy dissipation under mechanical loading--critical factors for load-bearing implants. Furthermore, TiO\({}_{2}\) acts as a suitable interlayer for HAp coatings by enhancing mechanical bonding and adhesion strength [5]. Due to its high hardness, biocompatibility, and antibacterial properties, TiO\({}_{2}\) has proven to be a multifunctional interface for implant applications [6]. To further enhance bioactivity, HAp is frequently employed as a surface coating due to its chemical and structural similarity to bone mineral. HAp is non-toxic, biocompatible, and osteeconductive and promotes long-term osseointegration [7; 8; 9; 10; 11]. Moreover, HAp presents valuable properties such as sinterability, resorbability, and controlled solubility, all of which contribute to its suitability for biomedical applications [10; 12; 13]. In recent years, green synthesis methods have gained attention for the production of HAp, using plant extracts as bio-templates. These approaches reduce the need for toxic reagents or high-energy processes, offering a more sustainable alternative [14; 15]. In this work, HAp was synthesized using extracts from _Hylocereus undatus_ cladodes, a cactus species rich in flavonoids, terpenoids, and phenolic compounds, offering an eco-friendly and functional enhanced route for biomedical surface coatings [15]. Among the available deposition techniques, electrophoretic deposition (EPD) has been extensively explored for HAp applications, particularly when using pre-synthesized powders or doped HAp derived from green methods [16; 17; 18; 19]. EPD is a process where charged particles in a suspension migrate under the influence of an electric field and are then deposited as a uniform layer onto the substrate [16; 17; 18; 19]. The process is simple, low-cost, and adaptable to a wide range of materials and geometries [17; 19]. [PERSON] et al. [18] prepared HAp coatings with controlled porosity using EPD and carbon black as a porogen agent, showing the method's adaptability. [PERSON] et al. [20] demonstrated the feasibility of depositing chemically precipitated HAp on Ti-6 Al-4V as early as 1997.