Flower-like titanium dioxide as novel co-reaction accelerator for ultrasensitive “off–on” electrochemiluminescence aptasensor construction based on 2D g-C3N4 layer for thrombin detection

An ultrasensitive “signal-off–on” electrochemiluminescence (ECL) biosensor is constructed based on f1-TiO 2 /g-C 3 N 4 /PDA for thrombin detection. The flower-like titanium dioxide (f1-TiO 2 ) has a huge specific surface area, which can not only increase the capacity of 2D graphite-like carbon nitride (g-C 3 N 4 ) layer, but also promote the action of coreactants, and the ECL intensity of the electrode modified with f1-TiO 2 /g-C 3 N 4 /PDA is 3.5 times higher than the electrode modified with g-C 3 N 4 /PDA. The carboxylated thrombin aptamer (sDNA) is incubated onto the modified electrode by amide bond; then, the complementary strand of thrombin aptamer (tDNA) modified with ferrocene is connected to the electrode surface by complementary base pairing with sDNA. Due to the ferrocene can quench the ECL of g-C 3 N 4 , the ECL signal decreases, while the ECL signal is restored in the presence of the target thrombin (TB). When K 2 S 2 O 8 and H 2 O 2 are used as a co-reactant, the ECL aptasensor for TB detection is constructed with a concentration variation from 10 −11 to 10 −5  M, which has a excellent sensitivity, and the detection limit is 8.9 × 10 −12  M. It also shows good specificity, reproducibility, and stability. This novel ECL aptasensor has potential application in human thrombin assay.