The interactions of chromium species in different oxidation states with a calf thymus DNA (ctDNA) have been investigated. The extent of ctDNA damage η measured as the relative change in the charge used for 8-oxoguanine (8-oxoG) electrooxidation determined using linear scan voltammetry. The values of η determined after the interactions of a ctDNA film with Cr species under various conditions, such as: (i) Cr(VI), (ii) Cr(VI) at -0.2V, and (iii) Cr(III) + UV radiation + O2, were found to be: 6.2±1.5, 1.24±0.40, and 0.93±0.31%, respectively, indicating that the highest damage to DNA is done by Cr(VI) species followed by the intermediate valency Cr species. The EIS measurements indicate that the exponential factor φ of the constant phase element (CPE) in the Ershler-Randles equivalent circuit was not strongly affected by the interaction of the DNA film with Cr species (maximum increase from φ = 0.80 to 0.84 after Cr(VI)-induced damage to DNA). This behavior contrasts with the behavior of charge transfer resistance (Rct), which decreases considerably after the interactions with Cr(VI) species causing oxidative ctDNA damage and structural changes in ctDNA film, lowering the barrier for the interfacial charge-transfer process. Only Cr(III) species, which are not potent oxidants, have not induced any damage to ctDNA, although they bind to the ctDNA and block efficient redox probe access to the Au electrode surface, thus increasing the value of Rct. The Warburg impedance was also strongly affected by the interactions of ctDNA with Cr(VI). In this case, the circular dichroism measurements show extensive damage to the ctDNA interbase hydrogen bonding which is likely due to the guanine oxidation and strand breaks.

Oxidative damage of DNA caused by chromium species

254th National Meeting (2017)

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