Comparison of hemoglobin and myoglobin for in situ metabolite generation in chemical toxicity sensors using a metallopolymer catalyst for DNA damage detection

Detection of DNA damage can serve as the basis for rapid, inexpensive screening of the toxicity of new chemicals. Sensors for this purpose can be constructed on electrodes using layer-by-layer electrostatic adsorption of DNA and bioactivating proteins that mimic liver cytochrome P450s. This paper evaluates the use of the inexpensive protein hemoglobin (Hb) as the bioactivating "enzyme" in such sensors. Stable films containing myoglobin (Mb) and DNA, and Hb and DNA, were assembled one layer at a time on rough pyrolytic graphite (PG) electrodes on top of a 900 nm thick layer of chloro-bis(bipyridyl)ruthenium(II)-poly(vinylpyridine) [PVP-ClRu(bpy)(2)(2+)], a catalyst for DNA oxidation. The films showed independent, chemically reversible voltammetric peaks for protein heme Fe-III/Fe-II and polymer Ru-III/Ru-II redox sites. Incubation of PVP-ClRu(bpy)(2)(2+)-(DNA/protein)(3) films in pH 5.5 buffer containing styrene and hydrogen peroxide over 15 min resulted in nearly linear increases in catalytic square-wave voltammetric (SWV) peaks at the Ru-II oxidation potential of ca. 0.73 V (vs. SCE). Films using Hb performed equally well as those containing Mb. No significant changes in SWV peaks were found for control incubations with toluene and hydrogen peroxide, styrene without hydrogen peroxide, or hydrogen peroxide alone.