**4. Nanoparticles**

Nanomaterials consists of materials that the size of particle is less than 100 nm. All kinds of materials could be treating to be nanomaterials such as metallic, nonmetallic, ceramics, polymeric and so on..

#### **4.1 Metal-based nanoparticles**

The widely used metallic nanoparticles in the field of medicine and biotechnology are gold (Au), platinum (Pt), silver (Ag), selenium (Se), copper (Cu), palladium (Pd), and gadolinium (Gd), also, the widely used metal oxide nanoparticles in the field of medicine and biotechnology are iron oxide (Fe2O3), titanium oxide (TiO2), and zinc oxide (ZnO). The metallic nanomaterials can be prepared and modified with appropriate chemical functional groups to bind with drugs, antibodies, and ligands.
