Light-scattering submicroscopic particles as highly fluorescent analogs and their use as tracer labels in clinical and biological applications.

In a companion article we present the idea that submicroscopic light-scattering particles, such as gold and silver particles, can be used as fluorescent analog tracers in biological and clinical applications. The light-emitting power and scattered light color of the particles can be adjusted by changing particle composition or diameter. Using Rayleigh and Mie light-scattering theory, we calculated the absorbance and light-scattering properties and power of particles of different diameters and selected compositions and compared them to the properties of fluorophores. In the present article, we evaluate experimentally the optical properties of particles of selected compositions and sizes and compare the results with the theoretically calculated values. We also discuss the methods which we use to measure the light-scattering properties of particles in suspension and to view individual particles by light microscopy. We also outline examples which demonstrate the use of light-scattering particles as fluorescent analogs in biological and clinical applications.