Raman Micro-spectral Imaging of Cells and Intracellular Drug Delivery Using Nanocarrier Systems

Raman microscopic imaging of eukaryotic cells has become a well-established technique to address various biochemical questions related to cell biology. The combination of Raman spectroscopy with optical microscopy offers the possibility to study the composition of cells and alterations associated with metabolistic activity induced by internal or external factors. Because of the associated spectral information obtained, Raman microscopy can be utilized without the need for fluorescent dyes or laborious sample preparation. In order to contrast the cellular compartments within the cytosol, imaging algorithms based on multivariate data analysis are commonly employed. Apart from imaging the intracellular organelles and structures of eukaryotes based on their intrinsic biochemical composition, it is possible to follow the uptake of various substances. Externally administered molecules can be labeled with stable isotopes, such as deuterium. The unique spectroscopic features of isotopically labeled compounds provide high specificity and sensitivity without changing the chemical properties of the molecules of interest. The concept of isotopic labeling is illustrated for the uptake of lipids into macrophages, as well as for liposomal drug delivery systems.