New Fluorescent Antitumour Cisplatin Analogue Complexes. Study of the Characteristics of their Binding to DNA by Flow Injection Analysis

The flow injection technique is applied to study the binding to DNA of new platinum complexes—E₁: ethylenediaminechlorocholylglycinateplatinum(II): [PtCl(CG)(en)], C₅₄H₉₂O₁₂Pt and E₂: ethylenediaminebischolylglycinateplatinum(II): [Pt(CG)₂(en)], C₂₈H₅₀ClN₃O₆Pt—derived from cisplatin in which the exchangeable ligands were replaced by bile acids, such that these anticancer drugs have less toxicity and less resistance is developed towards them. Both compounds are fluorescent and their fluorescence is enhanced when they form adducts with DNA, a property that is extremely useful for monitoring the cytotoxic activity and their mechanisms of action. The binding parameters to DNA of E₁ [apparent intrinsic binding constant K_E1: (11.2 ± 0.4) × 10³ M⁻¹ and maximum number of binding sites per nucleotide, n _E1: 0.121 ± 2 × 10⁻³) and E₂ (K_E2: 9.2 ± 0.7) × 10³ M⁻¹ and n _E2 0.098 ± 2 × 10⁻³] were determined following the Scatchard method and the type of binding was studied experimentally through the modifications introduced by each of the compounds into the ethidium bromide–DNA bond.