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A DNA damage Biosensor based on Copper Nanocluster and Carbon Dots for early diagnostics of cancer

An easy, cost effective and visually detectable method for biosensing of abasic site damaged lesion in DNA by using copper nanoclusters (Cu NCs) and carbon dots (CDs) as fluorescent probes is reported. Following this method, the presence of abasic sites in DNA could be visually detected in presence of only UV light without any instruments. Accumulation of potentially mutagenic abasic sites lesions in DNA are often considered as stress induced biomarker for radiation exposure and carcinogenesis. DNA containing numerous solitary or clustered abasic sites may potentially induce chromosomal abnormalities, mutations, aging related diseases and metastasis. Thus, detecting abasic sites in DNA is crucial for diagnosis of many diseases including immunodeficiency, cancer and for precautions for preservation of genomic integrity. 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. This is reported in the journal Sensors and Actuators B: Chemical, doi.10.1016/j.snb.2017.08.100 ( This work was done by Dr. Prolay Das and his graduate student Seema Singh, Department of Chemistry, IIT Patna in collaboration with Dr. Manoj K. Singh, BARC, Mumbai.