A carbon dot and gold nanoparticle-based fluorometric immunoassay for 8-hydroxy-2'-deoxyguanosine in oxidatively damaged DNA.

A method is described for the fluorometric determination of DNA containing oxidatively damaged product 8-hydroxy-2'-deoxyguanosine (DNA-8-OHdG). Carbon dots (CDs) were modified with glutaraldehyde for DNA conjugation, and antibody against 8-OHdG was immobilized on gold nanoparticles (AuNPs). The presence of DNA-8-OHdG can be linked to CDs by reaction of amino groups on DNA with glutaraldehyde. AuNPs were brought closely to CDs by specific immune reaction between 8-OHdG and antibody on AuNPs. Under 350 nm photoexcitation, the emission of CDs with a peak at 440 nm is quenched by the AuNPs and not restored. In the presence of DNA-8-OHdG, the measured fluorescence intensity decreases and quenching efficiency increases. The limit of detection is 700 pM, and the assay works in the 0.01 nM to 25 μM DNA-8-OHdG concentration range. The method is perceived to possess a good potential as a tool for detecting biomarkers for DNA damage due to oxidative stress. Graphical abstract A fluorometric immunoassay for detecting 8-hydroxy-2'-deoxyguanosine (8-OHdG) in oxidatively damaged DNA is reported. It is based on the use of carbon dots (CDs) and gold nanoparticles (AuNPs). Black wavy lines represent DNA. Yellow polygonal sharps represent 8-OHdG. Blue and pink balls represent CDs and AuNPs, respectively.