Abstract

Functionalized nanoparticles have been used in a number of different studies, including detection of DNA at ultra low levels, immuno histochemistry and, more recently, as substrates for surface enhanced resonance Raman scattering (SERRS) based imaging approaches. The advantages of using metallic nanoparticles are that they are very bright in terms of their optical characteristics and also, if functionalized in a particular manner, provide a SERRS response to give a unique vibrational fingerprint. Here we present the functionalization of gold and silver nanoparticles in such a way that the enhancement effect can be greatly increased through biological recognition and, as such, this effectively turns on the SERRS effect. This process can give rise to exquisite selectivity in terms of the interaction of the nanoparticles, especially when DNA hybridizations are used, and single base mismatches can be analyzed at room temperature. Dye oligonucleotide silver nanoparticles (DOSN) have also been used to detect double-stranded DNA through triplex formation to switch on the SERRS and a distance relationship between nanoparticles and SERRS response has been established for the first time. In an advancement of this approach, functionalized nanoparticles have also been used as imaging agents for single cells and, when functionalized with an appropriate antibody, can give back information on the expression of specific receptors on cell surfaces, as well as sub-cellular compartmentalization information. Finally, in moving away from the in vitro applications, the functionalized nanoparticles can be modified in such a way that they are active in vivo and preliminary data relating to in vivo studies of imaging and therapeutic uses of functionalized SERRS active nanoparticles will also be presented. This presentation covers the full range of design, the optical properties, and finally the biological properties of functionalized nanoparticles in relation to specific disease states.