Target-induced ratiometric electrochemical aptasensor for highly sensitive detection of thrombin based on AuNPs-MXene

Development of specific and sensitive electrochemical sensing platform for thrombin (TB) analysis is highly desirable for its important roles in many diseases. Herein, we designed and explored a facile ratiometric electrochemical aptasensor for TB detection based on signal on-off strategy. AuNPs-MXene was synthesized, characterized, and used to functionalize the basic electrode as a signal-amplified sensing platform. Hairpin probe (Hp) labeled with ferrocene (Fc) as signal probe, TB aptamer (TBA) labeled with methyl blue (MB) as capture probe are rationally introduced to fabricate highly-selective recognition and ratiometric dual-signal readout aptasensor. The sequence of Fc-Hp was designed to be complementary with MB-TBA to form a double-stranded DNA structure. When TB is present, the specific interaction between MB-TBA and TB leads to the departure of MB-TBA and the formation of hairpin structure of Fc-Hp, resulting in the leaving away of MB and confining Fc group near the electrode surface. Consequently, the oxidation peak current (I-pa) of Fc increased (signal-on), meanwhile I-pa of MB decreased (signal-off). Thus, the specific recognition of MB-TBA to TB can be read out in an electrochemical signal on-off ratiometric mode. A novel ratiometric electrochemical aptasensor was constructed with a wide linear range of 5.0 fmol/L similar to 1.0 pmol/L and a low detection limit of 1.7 fmol/L (3S(0)/S). Moreover, this ratiometric electrochemical aptasensor shows excellent selectivity, outstanding sensitivity, and good stability in real serum sample analysis, exhibiting promising potential application in bioanalysis.