Capillary electrophoretic separation and laser-induced fluorescence detection of the major DNA adducts of cisplatin and carboplatin.

Micellar electrokinetic capillary chromatographic separation of a dansylated mixture of normal nucleotides and platinated cross-link adducts of d(pGpG) and d(pApG) was optimized with baseline resolution. The introduction of a laser-induced fluorescence (LIF) detector overcame the lack of sensitivity characteristic of capillary electrophoresis (CE) due to the small injection volume and the short optical path length. CE/LIF was able to detect 1 adduct/10(4) normal nucleotides/micrograms DNA by fluorescence postlabeling assay. The enrichment of the adduct, prior to dansylation, enhanced the detection limit to 1 adduct/10(7) normal nucleotides/micrograms DNA. Calf thymus DNA was reacted in vitro with cisplatin and carboplatin with total input drug/nucleotide ratios of 0.05 and 0.5, respectively. A2780 human ovarian carcinoma cells were exposed in culture to 25 microM cisplatin for 2 h. The cells were incubated with drug-free medium for 3 h before harvesting. The identification of the cross-link adducts in modified DNA was confirmed by cochromatography with authentic markers. The same 1,2-intrastrand cross-link adducts were induced by both cisplatin and its second-generation drug carboplatin. This report has demonstrated, for the first time, the utility of CE/LIF as an analytical tool for assaying DNA damage [corrected].