In the biological sciences, gold particles have been used as high-contrast staining agents practically since the beginning of electron microscopy. The presentation focuses first on optical properties such as light absorption by plasmon resonance, Mie scattering, enhancement of Raman scattering and optical generation of heat gradients and their applications in microscopy. Secondly, the importance of the chemical stability of the particles for all applications is emphasized, and ways of achieving supreme stability by the preparation of so-called monolayer protected clusters (MPCs) is discussed. It is concluded with a range of bioanalytical applications that have been recently developed. These include the use of MPCs as markers for DNA, protein and peptide arrays as well as a new colorimetric high throughput approach to the screening of potential kinase inhibitors using MPCs as artificial substrates for kinase-catalysed phosphorylation.
