Abstract
A DNA-based biosensor is presented that can be applied to the detection of DNA damage caused by UV-C radiation (254 nm) in the presence of CdTe quantum dots (QDs). The sensor is composed of a glassy carbon electrode whose surface was modified with a layer of dsDNA and an- other layer of CdTe QDs. The response of this sensor is based on (a) the intrinsic anodic signal of the guanine moiety in the DNA that is measured by square-wave voltammetry, and (b) thecyclicvoltammetricresponseoftheredoxindicatorsystem hexacyanoferrate(III/II). Depending on the size of the QDs, they exert a significant effect on the rate of the degradation of dsDNA by UV-C light, and even by visible light. Time- dependent structural changes of DNA include opening of the doublehelix (as indicated byanincrease inthe redox response of the guanine moiety due to easy electron exchange with the electrode when compared to the original helix state and by an increase in the voltammetric peak current of the hexacyanoferrate(III/II) anion after degradation of the nega- tively charged DNA backbone on the electrode). The effects of QDs were verified for salmon sperm DNA and calf thymus DNA,andfurthercorroboratedbyexperimentsinwhichDNA solutions were irradiated in the presence of QDs.
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