A versatile turn-on fluorometric biosensing profile based on split aptamers-involved assembly of nanocluster beacon sandwich

•Nanocluster beacon is first used to develop split aptamer-based biosensors.•Target-induced proximity of split aptamer can light up nanocluster beacon.•The formation of sandwich complex based on nanocluster beacon and targets. As an important member of the aptamer family, split aptamers are used to enhance the sensitivity of aptasensors by forming a sandwich structure with target molecules. Here, we explored whether it is feasible to construct a fluorescent tunable biosensor by tethering a nanocluster beacon (NCB) pair, which is composed of DNA-silver nanoclusters (DNA-AgNCs) and a G-rich enhancer sequence (GRS), at each end of split aptamers. The addition of the target generates the formation of nanocluster beacon sandwich (NCBsandwich), resulting in fluorescence enhancement because of the proximity of DNA-AgNCs and GRS. This strategy is applied to build versatile aptasensors for the sensitive analysis of small molecules including adenosine, cocaine, and 17β-estradiol with detection limits of 40 pM, 35 pM, and 15 pM respectively. We have also shown that the NCB pair can be properly lengthened to bypass steric hindrance, allowing this strategy to be used to probe macromolecules such as thrombin. Evidence has also revealed that the high sensitivity in this system relies on the advanced properties of the NCB. The analysis of targets in human serum was also accomplished to illustrate the practical specificity and reliability of this method. This is the first attempt to incorporate NCBs into the design of a split aptamer-based biosensor.