Sub-cellular drug interaction and distribution are the key parameters in our studies on mechanism of action of anticancer agents and in exploring the novel strategies for chemotherapy of cancer. Confocal spectral imaging (CSI) based on the intrinsic drug fluorescence provides the distribution maps of different molecular forms of the drug. Coupling fluorescence and SERRS (surface-enhanced resonance Raman scattering with silver nano-colloids) at the same CSI map allows to join the advantages of these complementary methods.
Simultaneous detection of SERRS and fluorescence of anticancer drug mitoxantrone within a single living cancer cell (MCF-7) by confocal spectral imaging. Bottom left window shows the reference spectra of a) fluorescence of drug-DNA complex (red); the drug fluorescence in high and low polarity environment (blue and violet, respectively); b) SERRS of the drug (green). Fitting the intracellular spectra with the reference ones provides the respective quantitative maps (monochrome images) that can be superposed (multicolor image) to analyze their colocalisation with cellular compartments: nucleus (red); polar cytosolic regions (blue); cellular membrane and those of organelles (violet). The SERRS map indicates the co-localization of silver colloid aggregates with the membranes.
Technical details. A LabRAM microspectrometer (300 '/mm grating) was used with a 632.8 nm line of a built-in HeNe laser. The laser power at the sample was ~ 30 µW; the maps contain ~ 25 × 25 spectra recorded in point-by-point scanning mode (0.02 sec per spectrum) through a ×100 objective.
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