Biosensing of solitary and clustered abasic site DNA damage lesions with copper nanoclusters and carbon dots

Accumulation of potentially mutagenic abasic sites lesions in DNA are often considered as stress induced biomarker for radiation exposure and carcinogenesis. A simple and cost-effective fluorescence based method for detection of abasic sites in dsDNA is demonstrated. DNA was used as a template for copper nanoclusters (Cu NCs) formation. Presence of abasic sites in DNA hinder the formation of Cu NCs resulting in increased presence of Cu(II) in solution. These free copper ions were traced quantitatively by fluorescence quenching of carbon dots (CDs) in solution that report the presence of abasic sites in those DNA samples. Apart from fluorescence properties, binding of Cu NCs are markedly different for normal and abasic sites containing DNA. To demonstrate the inclusiveness of Cu NCs and CD based biosensing of abasic sites, oligomeric DNA, plasmid DNA in linear and condensed form and DNA extracted from onion and HeLa cells were tested and respond sensitively to the presence of abasic sites in nanomolar range of those DNA that is visually noticeable with UV light. The detection strategy works very well for clustered abasic sites DNA damage also, where multiple abasic sites lesions are present in close proximity in DNA and easily detectable by this method through visual inspection under UV light.