Surface enhanced IR absorption of nucleic acids from tumor cells: FTIR reflectance study.

The data on surface enhanced IR absorption (SEIRA) of nucleic acids deposited on a metal substrate were obtained using FTIR in reflectance mode. A 200-400 A thick gold film on a glass plate was the metal substrate. The approximate enhancement factors of the SEIRA for different vibrations of nucleic acids in our experimental conditions were 3-5. The roughness of the Au surface was about 50 A. Application of this method to nucleic acids isolated from tumor cells revealed some possible peculiarities of their structural organization, namely, the appearance of unusual sugar and base conformations, modification of the phosphate backbone, redistribution of the H-bond net, and so forth. This method enhanced a set of the bands, which is impossible to observe in conventional IR geometry. The SEIRA spectra of the RNA from tumor cells showed more sensitivity to the grade of tumor malignancy than the spectra of the DNA. After application of the anticancer drug doxorubicin to sensitive and resistant strains, the DNA isolated from these strains had different spectral features, especially in the region of the phosphate I and II bands. As induced by anticancer drugs, the conformational changes in the DNA from resistant and sensitive cancer strains could be characterized with different levels of structure disordering.

The SEIRA spectroscopy data of nucleic acids and phospholipids from sensitive- and drug-resistant rat tumours.

It is known that tumour progression towards drug resistance is one of the main factors resulting in the failure of cancer treatment. As tumour progression is based on the genetic instability, the study of the structure of nucleic acid from tumour cells is of great importance both for basic knowledge and for biomedical application. We applied surface enhanced infrared absorption spectroscopy (SEIRA) of nucleic acids on gold substrate and essentially increased the sensitivity of IR spectroscopy. We observed numerous changes in infrared spectra of DNA from sensitive and resistant cells that reflect drastic changes in molecular structure of DNA from tumour cells. The DNA from resistant cancer cells could be characterised as rigid structure, the structure of DNA from sensitive cancer strain seems to be flexible and after application of anticancer drugs drastically changes and approaches to the structure of helix forms. The molecular structure of lipids from resistant and sensitive cancers after application of anti-tumour drugs is also modified. Thus, we observed a disordering in the lipid chain packing from resistant cells after application of cisplatin and, in some cases, formation of phospholipid-Pt complex.