Evaluation of DNA-targeted anti-cancer drugs by Raman spectroscopy

Five triphenyl phosphonium salts including N-phenylacetamidyl triphenyl phosphonium chloride (1), N-phenylpropanamidyl triphenyl phosphonium chloride (2), ethyl 2-methylacetatyl triphenyl phosphonium chloride (3), ethyl butyryl triphenyl phosphonium chloride (4) and hexadecyl triphenyl phosphonium bromide (5) were synthesized and then were characterized by FT-Raman spectroscopy. Surface-enhanced Raman spectroscopy (SERS) in conjunction with electronic absorption spectroscopy was employed to study their interaction with DNA. The decreasing of Raman intensity at 1000, 1029, 1103 and 1588 cm−1 from compound 5 indicated that this compound has affinity for DNA. This was probably because compound 5 inserted into DNA and a new conjugated system was formed. The results of electronic absorption spectra were coincident with those of SERS. On the other hand, compound 5 showed a significant higher inhibitory rate on human cervix cancer cells. The targets of the compounds in the anti-cancer process were discussed. The mechanism of the anti-cancer process of compound 5 might be related to its interaction with DNA.