Chemical analysis in vivo and in vitro by Raman spectroscopy--from single cells to humans.

The gold standard for clinical diagnostics of tissues is immunofluorescence staining. Toxicity of many fluorescent dyes precludes their application in vivo. Raman spectroscopy, a chemically specific, label-free diagnostic technique, is rapidly gaining acceptance as a powerful alternative. It has the ability to probe the chemical composition of biological materials in a non-destructive and mostly non-perturbing manner. We review the most recent developments in Raman spectroscopy in the life sciences, detailing advances in technology that have improved the ability to screen for diseases. Its role in the monitoring of biological function and mapping the cellular chemical microenvironment will be discussed. Applications including endoscopy, surface-enhanced Raman scattering (SERS), and coherent Raman scattering (CRS) will be reviewed.