DNA-templated Au nanoclusters coupled with proximity-dependent hybridization and guaninerich DNA induced quenching: a sensitive fluorescent biosensing platform for DNA detection

In this paper, the fluorescence signal of poly( A) DNA- templated Au nanoclusters ( AuNCs) is found to be greatly quenched by photoinduced electron transfer ( PET) when they are close to guanine ( G)- rich DNA. Based on the findings, we have designed a low- cost fluorescence biosensing strategy for the sensitive detection of DNA. Highly luminescent and photo- stable poly( A) DNA- AuNCs were utilized as the fluorescent indicator and G- rich DNA was utilized as the fluorescent quencher. In the absence of target DNA, DNA- AuNCs failed to hybridize with the G- rich DNA and did not form the duplex DNA structure. Strong fluorescence intensity at 475 nm was observed due to the DNA- AuNCs being far away from the G- rich DNA. However, in the presence of target DNA, the DNA- AuNCs together with G- rich DNA could hybridize with the target DNA, leading to the 5 0 terminus of the DNA- AuNCs and the 3 0 terminus of Grich DNA being in close proximity and promoting the cooperative hybridization. Therefore, a Y junction structure was formed and the G- rich sequences were brought close to the AuNCs. Therefore, the fluorescence intensity of the sensing system decreased significantly. Taking advantage of the poly( A) DNA- templated Au nanoclusters and G- rich DNA proximity- induced quenching, the strategy could be extended to determine other biomolecules by designing appropriate sequences of DNA probes.