**1. Introduction**

Biomedical material is any substance that has been engineered to interact with biological sys‐ tems for a medical purpose, which may be therapeutic (i.e., to treat, augment, repair, or replace malfunctioning tissue in the body) or diagnostic. Among the various types of biomedical materials, metallic materials are the most widely used because of their high load‐supporting capacity, desirable qualities of wear and friction, and acceptable biocompatibility. Stainless

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steel, titanium, and their alloys are considered especially promising materials for surgical instruments and implants of many types and sizes. Polymeric materials have also garnered considerable interest in research and development as soft‐ and hard‐tissue replacements, on the basis of the ease of manufacturing and modifying such materials, and their appropriate physical, chemical, and mechanical properties.

When biomedical materials come in contact with physiological tissue and body fluids, vari‐ ous interactions, such as corrosive reaction, inflammation, and host response, are triggered. For this reason, knowing and understanding the surface properties of biomedical materials are crucial. Unfortunately, metallic materials are easily influenced by corrosion damage due to electrochemical reactions; additionally, the bioinertness and hydrophobic surface prop‐ erties render polymeric materials unfavorable for cell adhesion. Long‐term clinical experi‐ ments have also indicated that the primary causes of implant failure include not only unstable implant fixation to bone tissue, but also bacterial infection.

To overcome the aforementioned problems, a surface modification technique that uses a mul‐ tifunctional titanium dioxide (TiO2 ) coating is introduced to provide anticorrosive, antimicro‐ bial, and bioactive properties for the underlying biomaterial. These versatile natural features of TiO2 are attributed to its stable bonding structure, photocatalytic characteristics, and negatively charged surfaces. In this paper, a brief overview of TiO2 coating modification in the field of bio‐ medical material is provided. The two main topics discussed in the next section are as follows:

