A novel quantum dots-based OFF–ON fluorescent biosensor for highly selective and sensitive detection of double-strand DNA

We have developed a novel biosensor for the rapid determination of double-strand (ds) DNA based on the photoinduced electron transfer (PET) from glutathione (GSH) capped CdTe quantum dots (QDs) to praseodymium(III)–rutin (Pr3+–rutin) complex. The biosensor was based on a fluorescence “OFF–ON” mode. To provide the platform for dsDNA detection, the Pr3+–rutin complex was first employed as an effective fluorescence quencher to QDs through PET. Because of its strong binding affinity with Pr3+–rutin complex, dsDNA can break up the low fluoresced ionic ensemble, set free the luminescent QDs. Thus, the recognition of dsDNA by Pr3+–rutin complex can be realized through the restoration of QDs fluorescence. The relative recovered fluorescence intensity is directly proportional to the concentration of herring sperm (hs) DNA between 0.0874 μg mL−1 and 20 μg mL−1, and the detection limit (3δ/K) is 0.0262 μg mL−1. The entire experimental process does not require any chemical modification and coupling of CdTe QDs and dsDNA, greatly simplifying the experimental process. Some possible reaction mechanisms are discussed.