Monofunctional platinum complexes containing a 4-nitrobenzo-2-oxa-1,3-diazole fluorophore: Distribution in tumour cells

Two monofunctional platinum(II) complexes, cis-[PtL(NH3)(2)Cl]NO3 (1) and cis-[PtL'(NH3)(2)Cl]NO3 (2) {L = N-methyl-7-nitro-N-(2-(pyridin-2-yl)ethyl)benzo[c][1,2,5]-oxadiazol-4-amine, L' = 7-nitro-N-(2-(pyridin-2-yl)ethyl)benzo[c][1,2,5]oxadiazol-4-amine}, have been synthesized and characterized. The X-ray single crystal structure of complex 1 shows that platinum(II) is coordinated in a square-planar geometry with a [PtN3Cl] setting. Fluorescence profiles of the complexes show that complex 1 is more suitable for cellular imaging than complex 2. The cellular uptake and distribution of complex 1 in the human cervical cancer HeLa cells were studied using confocal microscopy. Complex 1 enters the cells slowly, induces cytoplasmic vacuolations, and accumulates in the nucleoli. These results suggest that monofunctional platinum(II) complexes can stimulate tumour cells to undergo a nonapoptotic death process, which is distinct from the apoptosis induced by cisplatin.