Biocompatible nanometal particle fluorescence enhancers.

Fluorometry has been used for more than a century to enhance the understanding of phenomena in molecular biology. With recent advances in light detection techniques, it is even more actively used in research now. The effectiveness of fluorometry highly depends on the intensity of the fluorescence from the target molecules in contrast to the background. Instrumentation for amplifying fluorescence signals may not selectively enhance signals only from the target. Therefore, a method to retrieve more fluorescence emission from a fluorophore is beneficial. Nanometal particles have high-density surface plasmon polariton fields, and when a fluorophore is placed within these fields, the electrons involved in the fluorescence emission may be altered in their energy states. The level of alteration depends upon the metal type, size of the particle, quantum yield of a fluorophore, and, most importantly, the distance between the nanoparticle and the fluorophore. Some organic solvents are also found to enhance fluorescence, possibly by the dipole-dipole coupling between the fluorophore and the solvent, resulting in an increase in the energy gap between the excited and the ground states. In this article, study results of the application of nanometal particles and biocompatible solvents for increasing the sensitivity/resolution in fluorophore-mediated biosensing/bioimaging are reviewed.