Application of semiconductor and metal nanostructures in biology and medicine

Advances in nanotechnology research have led to the creation of new generation of contrast agents, therapeutics, and delivery systems. These applications are expected to significantly improve the diagnosis and treatment of a variety of diseases. Two nanotechnologies-semiconductor and metallic nanostructures-are the most advanced in this young field and have been extensively investigated for clinical use. These nanostructures are currently the "model" for the developments of many novel nanostructures. This review describes their chemical design, tunable properties, and utility in medicine. Furthermore, we will describe the current understanding of their toxicity, which could be barriers to their use for human.