Detection of Chemically Induced DNA Damage by Derivative Square Wave Voltammetry

Abstract

Damage of DNA films after reaction with styrene oxide was detected using derivative square wave voltammetry. Double-stranded (ds) DNA films with initially low backgrounds developed oxidation peaks for DNA bases during incubation with styrene oxide. Films were prepared on pyrolytic graphite (PG) electrodes by casting mixtures of DNA with the poly(ester sulfonic acid) ionomer Eastman AQ38S or by covalent binding of DNA onto oxidized PG. While both types of films gave oxidation peaks in the region 0.6-1.1 V vs SCE after incubations with styrene oxide, DNA/AQ films gave the best signal-to-background ratios. Damage of DNA by reaction with styrene oxide under the electrode incubation conditions was confirmed by capillary electrophoresis. Total integrals of oxidation peaks increased with time of incubation with styrene oxide. Relative peak heights depended on the type of DNA in the order calf thymus ds DNA > salmon sperm ds DNA > supercoiled ds DNA > highly polymerized calf thymus ds DNA.

Electrochemical Sensors for DNA Interactions and Damage

“…On the other hand, techniques based on measurements of changes in the intensity of a signal yielded by intact DNA are in nature less sensitive, because the change in peak height should exceed standard deviation of the measurement (usually 5 ± 10% depending on the electrode material, surface pretreatment and DNA immobilization procedure). This means that when, e.g., peak G ox is measured at carbon electrodes [12,65,67,81,85,107,123], a portion of the lesions has to be at least about 10% of total G residues to achieve reliable response of the sensor. Regarding specificity, the best results can be obtained when signals derived from electroactivity of substances interacting with DNA are measured [8, 9, 12, 35, 52, 66, 102 ± 104, 131, 143, 144, 155].…”

“…Some authors utilized ™bulk modification∫ of the carbon paste with DNA, i.e., DNA modification of the carbon powder prior to mixing with the oil component of the paste [79,80]. Other techniques of DNA immobilization include preparation of ™thick DNA layers∫ by deposition of concentrated DNA solutions onto solid electrode surfaces followed by drying of the resulting DNA gels or films [63,81]. Although empirically optimized for given purposes, some of the approaches of DNA immobilization may result in poorly defined DNA layers, and hardly controllable events may occur during the analysis (e.g., leakage of water-soluble DNA from the bulk-modified carbon paste or from dried thick DNA films, changes in hydration of the latter, etc.…”

“…2A) and/or ii) the absence of extensive DNA surface denaturation effects at the carbon surfaces (reviewed in [8,9,23]). A relatively deep degradation of DNA (e.g., due to acid hydrolysis [99,100], oxidative DNA damage mediated by copper complexes [83] or chemical damage by styrene oxide [81]) is therefore required to observe significant increases in intensity of DNA signals at carbon electrodes. Labuda et al proposed a technique using an intercalative redox intercalator, [Co(phen) 3 ] 3 , for detection of DNA damage [59,60,79,83,101].…”

“…± has been reported and compared to a currently used bioluminescence toxicity test Toxalert 100[67]. Rusling et al investigated the damage of DNA films deposited on modified carbon electrodes by styrene oxide[81,85]. We have shown[57] that scDNAmodified mercury electrodes can be used as detectors for DNA strand-breaking agents not only in laboratoryprepared solutions, but also in samples of food and natural and industrial waters.6.3.…”

Detection of Chemically-Induced Damage in Layered DNA Films with Co(bpy)33+ by Square-Wave Voltammetry

“…We recently reported detection by direct oxidation of the damaged DNA in cast ionomer films using derivative square-wave voltammetry (dSWV) [21,22]. In these films, ds-DNA gave near featureless dSWV backgrounds.…”