Guests involved CB[8] capped silver nanoparticles as a means of electrochemical signal enhancement for sensitive detection of Caspase-3

Cysteine aspartase protease (Caspase-3) plays an important role in various diseases. In this work, silver nanoparticles (AgNPs) with electronic properties have been utilized as signal amplification elements for fabricating electrochemical Caspase-3 biosensor. In the presence of Caspase-3, the cleavage of substrate results in the exposure of a free phenylalanine at the end of the peptide, which can bind CB[8] specifically through host-guest reaction. To enhance the electrochemical signal, AgNPs further reacts with CB[8]. Through layer-by-layer assembly of AgNPs, nanostructure was formed via electrostatic cross-linking of AgNPs and CB[8], which can not only prevent the AgNPs' agglomeration, but also enhance the electrochemical signals. Furthermore, different guests (methylviologen and anthracene) were studied for its electrical transfer efficiency between electrode and AgNPs redox center. Among them, it was found methylviologen/CB[8] complex can increase the electrical conductivity and thus further enhance the Caspase-3 sensor's sensitivity. Under the optimized detection condition, the detection limit for Caspase-3 is 24.62 pg mL−1. Attribute to its simple and sensitive properties, the fabricated Caspase-3 electrochemical sensor has great potential in clinical applications.