A novel and sensitive turn-on fluorescent biosensor for the DNA detection using Sm3+-modulated glutathione-capped CdTe quantum dots

A novel and sensitive turn-on fluorescent biosensor for herring sperm DNA (hsDNA) detecting was designed based on hsDNA-induced fluorescence enhancement of Sm3+-modulated glutathione (GSH)-capped CdTe quantum dots (QDs). The fluorescent biosensor was based on the following two properties. First, the high fluorescence of GSH-capped CdTe QDs could be effectively quenched by Sm3+ due to the binding of Sm3+ to the GSH on the surface of the QDs and the electron transfer from the photoexcited GSH-capped CdTe QDs to Sm3+. Second, the high affinity of hsDNA to Sm3+ enabled Sm3+ to be dissociated from the surface of GSH-capped CdTe QDs to form more stable complex with hsDNA in aqueous solution, thereby enhancing the fluorescence of Sm3+-modulated GSH-capped CdTe QDs. Experimental results showed that the enhanced fluorescence intensity of Sm3+-modulated GSH-capped CdTe QDs was directly proportional to the concentration of hsDNA in the range from 0.012 to 14.0 μg mL−1 with a good correlation coefficient of 0.9977, and the detection limit (3σ/S) was 3.61 ng mL−1. To further investigate perfect analysis performance, the developed biosensor was applied to the determination of hsDNA in synthetic samples and human fresh serum samples with satisfactory results.