COMPARATIVE FT SERS, RESONANCE RAMAN AND SERRS STUDIES OF DOXORUBICINAND ITS COMPLEX WITH DNA

Fourier transform surface enhanced Raman scattering (FT SERS) coupled with a microscope has been used as a probe to obtain information on th e interaction of a drug and of its complex with DNA. Micro-FT SERS spe ctra of the antitumour agent doxorubicin (DOX) at 10(-5) M and of this complex with DNA have been recorded in aqueous silver hydrosol and co mpared with the corresponding resonance Raman (RR) and SERS spectra at concentrations of 5 x 10(-4) M and 5 x 10(-8) M, respectively. The in teractions between the drug and calf thymus DNA induced identical effe cts in the RR and visible SERS spectra. The data show that the adsorpt ion of the drug-DNA complex on the silver hydrosol does not induce det ectable perturbations of the molecular interactions within the complex . Micro-FT SERS spectra were found to be partially different from thos e obtained in visible SERS spectra. These differences concern the rela tive enhancement of some vibrational modes which could hardly be obser ved when resonance excitation was used. The FT SERS approach enables f urther information to be obtained and additional details on the geomet ry of the drug-DNA interaction to be revealed. An analysis of the FT S ERS spectra of the drug and of its complex with DNA not only confirms the model of interaction proposed using RR and SERS data in the visibl e, but brings about new information, especially on the vibrations of r ing A of the molecule, which are usually masked by the vibrations of r ings B and C dominant in the visible SERS spectra.