Incorporating elements of triple-helix aptamer probes (TAP), catalyzed hairpin assembly (CHA) signal amplification and host-guest recognition, a novel “signal-on” sensing strategy for sensitive electrochemical quantification of tetracycline (TC) was reported unprecedentedly. TAP was formed involving an aptamer loop, two-segment stems and a triplex oligonucleotide serving as trigger probe. Then, the trigger probe would be released from TAP once the target presented due to the conformational variation of TAP induced by aptamer binding event, sp...