A cathodic photoelectrochemical immunoassay with dual signal amplification for the ultrasensitive detection of DNA damage biomarkers.

Toxicity screening and risk assessment of an overwhelmingly large and ever-increasing number of chemicals are vitally essential for ecological safety and human health. Genotoxicity is particularly important because of its association with mutagenicity, carcinogenicity and cancer. Phosphorylated histone H2AX (γH2AX) is an early sensitive genotoxic biomarker. It is therefore highly desirable to develop analytical methods for the detection of trace γH2AX to enable screening and assessment of genotoxicity. Here, we developed a novel cathodic photoelectrochemical (PEC) immunoassay with dual signal amplification for the rapid and ultrasensitive detection of γH2AX in cell lysates. A sandwich immuno-reaction targeting γH2AX was first carried out on a 96-well plate, using a secondary antibody/gold nanoparticle/glucose oxidase conjugate as the labeled detection antibody. The conjugate increased the production of H ₂ O ₂ and thus provided the first mechanism of signal amplification. The immuno-reaction product containing H ₂ O ₂ was then detected on a photocathode prepared from Bi _2+x WO ₆ rich in oxygen vacancies, with H ₂ O ₂ acting as electron acceptor. The oxygen vacancies acted as both adsorption and activation sites of H ₂ O ₂ and thus enhanced the photocurrent, which provided another mechanism of signal amplification. As a result, an ultrasensitive immunoassay for γH2AX determination was established with a limit of detection of 6.87 pg/mL (S/N = 3) and a wide linear range from 0.01 to 500 ng/mL. The practicability of this assay was verified by detecting γH2AX in cell lysates exposed to known genotoxic chemicals. Our work offers a promising tool for the screening of genotoxic chemicals and opening a new avenue toward environmental risk assessment.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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