**Abstract**

During the past decade, research in the area of synthesis and applications of nanostructured titanium dioxide (NS TiO2) has become tremendous. NS TiO2 materials have shown great potential and a wide range of applications. The decrease in the particle size and the increase of the surface/volume ratio lead to the increase of the specific surface and the modification of the physicochemical properties and the appearance of new interesting properties (photocatalytic, optical, magnetic, electronic...). Their new morphology even allows the appearance of new biological properties. NS TiO2 can thus be used for the same applications as those known for their precursors before transformation and their nanostructures are accompanied by new properties allowing applications. This chapter briefly describes the synthesis process of the different NS TiO2, their chemical and surface modifications, and their application. The preparation of NS TiO2, including nanoparticles, nanorods, nanowires, nanosheets, nanofibers, and nanotubes is described. This chapter discusses the effects of precursor properties and synthesis conditions on the structure, crystallinity, surface specificity, and morphology of titanium dioxide nanoparticles. Recent advances in NS TiO2 in nano-biosensing, medical implants, drug delivery, and antibacterial fields, pharmaceutical applications, as well as their toxicity and biocompatibility, were presented.

**Keywords:** titanium dioxide nanoparticle, syntheses process, chemical methods, physical methods, biosynthesis, environmental applications, biomedical applications, biocompatibility
