NEAR-INFRARED FT-SERS MICROSPECTROSCOPY ON SILVER AND GOLD SURFACES -TECHNICAL DEVELOPMENT, MASS SENSITIVITY, AND BIOLOGICAL APPLICATIONS

An FT-Raman and PT-SERS microprobe with the spatial resolution on the micrometer scale has been developed. The main interfacing components a re discussed and the whole setup is validated with the use of differen t SERS-active substrates: silver and gold colloids and gold island fil ms. Micro-FT-SERS spectra of crocetin, mitoxantrone, and mitoxantrone/ DNA complexes have been obtained, and the mass detection limits are fo und to be on the order of 5 x 10(2) molecules. Adsorption on the SERS- active substrates does not induce any detectable changes in the all-tr ans configuration of the crocetin. Adsorption of the mitoxantrone/DNA complex does not induce detectable perturbations of the molecular inte ractions within the complex. Moreover, interactions between the drug a nd DNA induces very similar effects in both the resonance Raman and FT -SERS spectra of the drugs. These effects were found to be consistent with the model of mitoxantrone/DNA intercalation proposed from nuclear magnetic resonance and resonance Raman data. The signal-to-noise rati os found indicate that submonolayer amounts of intracellularly localiz ed drugs totaling less than 10(-18) mole can be detected by means of t he FT-SERS microprobe. Hence, both the extra-low mass detection limit of the technique and its sensitivity to interactions within the supram olecular complexes will in the future allow the drug to be followed wi thin the living cell.