Preparation and Biomedical Applications of the Plasmonic and Magnetic Nanoparticles Gold nanoparticles and application in IVD testing Gold (Au), silver (Ag) and iron oxide nanoparticles (NPs) are widely used in biomedical applications such as nanoprobes for detection of biochemical components, drug delivery and therapy because of their chemical stability, biocompatibility and unique optical/magnetic properties. Those properties strongly depend on their size, shape, degree of aggregation and the functional groups on their surface. Rapid advances in nanotechnology offer us a great opportunity to develop the controllable synthesis and modification of NPs as well as to study on their properties and applications. The size-controlled growth NPs requires the isotropic growth on the surface of nuclei whereas anisotropic growth will induce the formation of NPs of varying shape. Functionalized NPs provide sensitive and selective biosensors for the detection of many targets, including metal ions, small organic compounds, protein, DNA, RNA and cell based on their optical, electrical or electrochemical signals. The biomedical applications of those particles have been moving from laboratory study to the point of practical use.