A universal and label-free aptasensor for fluorescent detection of ATP and thrombin based on SYBR Green I dye

A facile and universal aptamer-based label-free approach for selective and sensitive fluorescence detection of proteins and small biomolecules by using the SYBR Green I (SGI) dye is developed. This robust versatile biosensing strategy relies on fluorescence turn-off changes of SGI, resulting from target-induced structure switching of aptamers. Upon binding with the targets, the aptamers dissociate from the respective cDNA/aptamer duplexes, leading to the release of the dsDNA-intercalated SGI into solution and the quenching of the corresponding fluorescence intensities. Such target-induced conformational changes and release of aptamers from the DNA duplexes essentially lead to the change in the fluorescence signal of the SGI and thus constitute the mechanism of our aptamer-based label-free fluorescence biosensor for specific target analyses. Under optimized conditions, our method exhibits high sensitivity and selectivity for the quantification of ATP and thrombin with low detection limits (23.4 nM and 1.1 nM, respectively). Compared with previous reported methods for aptamer-based detection of ATP and thrombin, this label-free approach is selective, simple, convenient and cost-efficient without any chemical labeling of the probe or the target. Therefore, the present strategy could be easily applicable to biosensors that target a wide range of biomolecules.