Peptide-Based Electrochemiluminescence Biosensors Using Silver Nanoclusters as Signal Probes and Pd-Cu2O Hybrid Nanoconcaves as Coreactant Promoters for Immunoassays

Metal nanoclusters (NCs) possess high light stability and biocompatibility because of their unique quantum size effect, which has gradually become a new type of electrochemiluminescence (ECL) nanomaterial for immunoassays. However, the luminescence efficiency of metal NCs is too low to meet the needs of trace analysis, which limits its application. Herein, Ag NCs served as signal probes and Pd-Cu2O hybrid nanoconcaves served as coreaction promoters, developing a highly efficient peptide-based biosensor for neuron-specific enolase (NSE) detection. Utilizing the reversible cycle of Cu+/Cu2+ and the reduction characteristics of Pd NPs, Pd-Cu2O greatly accelerates the reduction of S2O82-. Meanwhile, Pd-Cu2O has good hydrogen evolution activity, which promotes the generation of oxygen by improving the redox efficiency of the overall reaction, thus increasing the yield of active intermediates (OH•) to promote the reduction of S2O82-. Specially, this is an effective attempt to use the hydrogen evolution reaction (HER) to accelerate the ECL emission of the S2O82- system. In addition, a short peptide ligand (NARKFYKGC, NFC) was developed to implement the targeted immobilization of antibodies, which can specifically bind to the Fc fragment of antibodies, thereby avoiding the occupation of the antigen binding site (Fab fragment). The introduction of NFC not only improves the binding efficiency of antibodies but also protects its bioactivity, thus significantly improving the sensitivity of the biosensor. Based on these strategies, the proposed biosensor provides a new perspective for the applications of metal NCs in ECL systems.