Luminescent quantum dots as advanced biological labels

The development of optical-detection labels has substantially impacted many areas of biomedical research such as high-throughput drug screening, clinical diagnostics, and in vivo monitoring of gene expression and enzyme activity. These probes are traditionally based on organic dyes conjugated to biomolecules. Because of their complex molecular structures, however, organic fluorophores often exhibit unfavorable absorption and emission properties such as photobleaching, environmental quenching, broad and asymmetric emission spectra, and the inability to excite more than two to three colors at a single wavelength. These problems can be overcome by exploiting the unique optical properties of metal and semiconductor nanoparticles. In fact, recent research by several groups has linked such nanoparticles to peptides, proteins, and DNA and has demonstrated their applications in assembling new materials, in homogeneous bioassays, and in multicolor fluorescence imaging and detection.