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Platinum diam(m)ine anticancer complexes,such as cisplatin,are successful in clinic,but suffer from problems of resistance and side-effects.Photoactivatable Pt Ⅳ prodrugs offer the potential of targeted drug release and new mechanisms of action.1-3 We report visible-light activated diazido complexes trans,trans,trans-[Pt(N 3)2(OH)2(Am1)(Am2)](Am1 and Am2 = amines)that are inert in the dark towards hydrolysis and glutathione reduction,but undergo rapid photoreduction with UVA or blue light.Theses complexes exhibit rapid potent photocytotoxicity towards various cancer cells and form novel DNA lesions in cancer cells,with no activity in the absence of irradiation.2 When irradiated with UVA(λmax = 365 nm)or blue light(λ max = 420 nm,450 nm),they undergo photo-decomposition,releasing the azido ligands,N3 radical,N2 and O2 gases,as monitored by UV-Vis,14 N-NMR spectroscopy,GC-MS and EPR.The photoreactions of these complexes with 5-GMP rapidly formed Pt Ⅱ-5-GMP adducts,such as [Pt Ⅱ(N 3)(Am1)(Am2)(5-GMP)] + and [Pt Ⅱ(Am1)(Am2)(5-GMP)2 ] 2+,as judged by LC-MS and 195 Pt-NMR.Furthermore,an oxidized guanine,8-OH-G,was also found in the products.3 This indicate that Pt Ⅳ diazido complexes exert their anticancer effect not only by forming DNA adducts,but also by inducing oxidative stress.This result suggests that multiple mechanisms of action account for the high photocytoxicity of this class of compounds.