A Sensitive Electrochemical Aptasensor for Thrombin Detection Based on Electroactive Co-Based Metal-Organic Frameworks with Target-Triggering NESA Strategy.

In this work, an improved target-triggering nicking enzyme signaling amplification (NESA) strategy as signal enhancer has been fabricated to obtain a sensitive electrochemical thrombin (TB) biosensor combined with PtPd NPs decorated electroactive Co-based metal-organic frameworks (Co-MOFs/PtPdNPs) as a redox mediator. Traditionally, in the NESA strategy, only one of the output double strands DNA is available in the next cycle. However, in this work, all of the output DNA involved in the improved NESA strategies could be further employed, resulting in high utilization of output DNA, which further enhanced signal amplification and sensitivity of the biosensor. In addition, the electroactive Co-MOFs were not only used as nanocarriers but also acted as signal labels, avoiding adding extra redox media. Simultaneously, in the presence of H2O2, PtPd NPs decorated on the Co-MOFs act the same as horseradish peroxidase to promote the oxidation of H2O2, further promoting the conversion of Co2+ to Co3+, leading to electrochemical signal amplification. With such design, the TB biosensor exhibited good sensitivity from 1 pM to 30 nM with a detection limit of 0.32 pM. This new NESA strategy with high utilization of output DNA can supply one efficient approach to improve signal amplification, which also open an avenue for sensitivity enhancement in detection of analytes.