Surface modification using metal oxide materials enhances substrate properties like biocompatibility, corrosion resistance, and antibacterial activity, often applied to nanoparticles or implants such as titanium alloys. Physical methods include plasma spray for dense coatings like hydroxyapatite or Al₂O₃ on titanium, and physical vapor deposition (PVD) for uniform TiN films improving wear resistance. Chemical approaches encompass sol-gel for uniform oxide films like TiO₂, micro-arc oxidation for ceramic layers, and chemical vapor deposition (CVD) for controlled TiO₂ nanowires. Bio-inspired methods use catechol-based dispersants for strong adsorption on oxide nanoparticles, enabling electrophoretic deposition (EPD). Titanium dioxide (TiO₂), iron oxide, alumina (Al₂O₃), zirconia (ZrO₂), and silver oxide (Ag₂O) dominate, often doped with Ag, Sr, or Zn for added bioactivity. Silane coupling agents functionalize metal oxide nanoparticles to reduce agglomeration and improve dispersion in composites. Recent advances include block copolymer-templated metal oxide nanopillars on polymers for tailored surfaces. This article covers the study of functionalizing Fe₃O₄ and ZnO nanoparticles (NPs) for biocompatibility involves coating their surfaces with biocompatible materials to reduce toxicity, prevent agglomeration, and enhance stability in biological environments. Polyaniline (PANI) and aryldiazonium salts (ArN2+) are tried as coatings which minimize immune recognition and cytotoxicity up to considerable level. This surface functionalization improves biocompatibility as well efficacy of metal oxide sensors.