Amplified electrochemiluminescent aptasensor using mimicking bi-enzyme nanocomplexes as signal enhancement

In this work, a sandwich-type electrochemiluminescence (ECL) aptasensor for ultrasensitive detection of thrombin (TB) was designed based on mimicking bi-enzyme cascade catalysis to in situ generate coreactant of dissolved oxygen (O2) for signal amplification. We utilized hollow Au nanoparticles (HAuNPs) as carriers to immobilize glucose oxidase nanoparticles (GOxNPs) and Pt nanoparticles (PtNPs) by electrostatic adsorption. Then, the detection aptamer of thrombin (TBA 2) was immobilized on the PtNPs/GOxNPs/HAuNPs nanocomplexes. Finally, hemin was intercalated into the TBA 2 to obtain the hemin/G-quadruplex structure. The hemin/G-quadruplex was an interesting DNAzyme that commonly mimiced horseradish peroxidase (HRP). Herein, GOxNPs, hemin/G-quadruplex and PtNPs could form mimicking bi-enzyme cascade catalysis system to in situ generate dissolved O2 as coreactant in peroxydisulfate solution when the testing buffer contained proper amounts of glucose. This method had successfully overcome the disadvantage of difficulty to label the dissolved O2 and realized the ECL signal amplification. The experiment proved that the aptasensor had good linear relationship on low concentration of TB. The linear range was 1×10(-6)-10 nM, with a detection limit of 0.3 fM.