Ultrasensitive and versatile homogeneous electrochemical cytosensing platform based on target-induced displacement reaction for "signal-on" bioassay

We proposed, for the first time, a ultrasensitive amplification-free, label-free, and enzyme-free homogeneous electrochemical cytosensing platform based on the target-induced displacement reaction for tumor cell "signal-on" assay. To realize this proposal, the electroactive probe, [Fe(CN)(6)](3-), was entrapped in the pores of positively charged MSN (PMSN), and then the negatively charged aptamer of the tumor cell was adsorbed on the surface of PMSN as a biogate. Once the tumor cells were recognized and captured by the aptamer, the biogate could be efficiently opened and the entrapped [Fe(CN)(6)](3-) released, which can be ascribed to the decreased adhesion between the aptamer-cell complex and PMSN. Consequently, the electrochemical signal dramatically increased. Overall, the "signal-on" strategy was conveniently realized. Notably, the detection limit for tumor cells assay (13 cells/mL) is comparable to those of the reported methods Furthermore, based on the similar proposal, this biosensor also can be extended for the ultrasensitive detection of microRNA (38 aM, SIN = 3) and Hg2+ (0.47 pM, S/N = 3). Therefore, this biosensing platform has the great potential to be a powerful tool in the applications of disease diagnostics and environmental monitoring. (C) 2018 Elsevier B.V. All rights reserved.