Picomolar thrombin detection by orchestration of triple signal amplification strategy with hierarchically porous TiCT MXene electrode material-catalytic hairpin assembly reaction-metallic nanoprobes.

Signal amplification strategies are essential to boost the sensitivity of detecting targeted ions or molecules with important biological functions, while few studies take advantage of signal amplification strategies more than two. As a "proof-of-concept" demonstration, we present the ultrasensitive electrochemical aptasensor for picomolar thrombin detection by synchronous coordination of triple signal amplification strategy. The porous MXene framework (PMXF) with secondary pores is constructed as carrier to increase electrons transfer channels, and thionine (as redox indicator) labelled Au nanorod (AuNR) and hollow Cu-Pt alloy (HCuPtA) are synthesized as the electrical signal amplifiers to enhance the response signals. In the presence of picomolar-level thrombin, catalytic hairpin assembly reactions of DNA are triggered to bridge thionine labelled AuNR or HCuPtA nanoprobes on the PMXF with controllablly scondary pore structures. Under the optimal conditionals, the sandwich-typed aptasensor based on PMXF-5/AuNR shows a more low limit of detection (LOD) of 0.67 pM with a linear range from 2 pM to 10 nM, while PMXF-5/HcuPtA exhibits a more wide linear range from 50 pM to 50 nM with a LOD of 16.67 pM for thormbin. This sensing platform can be customized to analyze other biological or environmental substances at an ultrahigh level by rationally designing DNA sequences of target-binding aptamer.