A signal amplification strategy using the cascade catalysis of gold nanoclusters and glucose dehydrogenase for ultrasensitive detection of thrombin

This work reports a novel signal amplification strategy for ultrasensitive detection of thrombin by cascade catalysis of gold nanoclusters (AuNCs) and glucose dehydrogenase (GDH). Herein, the AuNCs prepared by using polyamidoamine dendrimer as template were constructed not only as nanocarriers for anchoring the large amounts of secondary thrombin aptamers but also as nanocatalysts to catalyze the oxidation of NADH efficiently. Moreover, a large amount of GDH was loaded through the immobilization technology of DNA hybridization and a large amount of toluidine blue (Tb) was intercalated into the DNA grooves via electrostatic interaction. Significantly, the electrochemical signal was greatly enhanced based on cascade catalysis: firstly, GDH catalyzed the oxidation of glucose to gluconolactone with the concomitant generation of NADH in the presence of NAD+. Then, AuNCs as nanocatalysts could effectively catalyze NADH to produce NAD+ with the help of Tb as redox probe. Under the optimal conditions, the proposed aptasensor exhibits a linear range of 1.0×10−14-5×10−9 M with a low detection limit of 3.3×10−15 M for thrombin detection and shows high sensitivity and good specificity.