Laccase-inspired bi-amino acid MOFs with high substrate affinity: Catalytic deposition induced "signal-down" electrochemical response towards PD-L1

A dual-ligand Cu-MOFs (Cu-F/Hs) based on phenylalanine (Phe) and histidine (His) was innovatively constructed with enhanced catalytic property. Among them, Phe can interact with the dopamine (DA) to enhance the substrate affinity. Meanwhile, the coordination of His with copper ions was inspired by the active site structure of natural laccase to improve the catalytic activity. The Km value of Cu-F/Hs was 0.14 times of laccase, indicating a high affinity for the catalytic substrate DA. Accordingly, a sensitive sensor for PD-L1 detection was designed by using Cu-F/Hs, which can catalyze DA to form redox-active polymeric conjugates deposited on the electrode surface with good electrical conductivity, thereby contributing a "signal-down" electrochemical response with a double signal enhancement. The detection limit was 0.12 ng/mL in the detection range of 0.5-200 ng/mL. This work provided a new and simple way to synthesize MOFs with high substrate affinity and efficient activity, and a general signal amplification strategy induced by the catalytic deposition.