Functional Au@Cu/Cu2O/C composites derived from 2D Cu-based metal–organic framework for sensitive label-free electrochemical immunoassay

Metal-organic frameworks (MOFs) face challenges in electrochemical sensing due to low conductivity and poor stability. Herein, we report the synthesis of MOFs-derived metal/carbon composites (Au@Cu/Cu₂O/C) that exhibit synergistic effects by combining metallic and carbonaceous characteristics due to their hierarchical structures and metal contents. The Au@Cu/Cu₂O/C composites were characterized using electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. These composites inherit the exceptional properties of the pristine MOFs while exhibiting a large specific surface area, high electrical conductivity and stability. As an excellent electrode material, the Au@Cu/Cu₂O/C composites were biofunctionalized with streptavidin and a biotinylated antibody for use as a highly sensitive, label-free electrochemical immunosensor for the detection of the tumor marker prostate specific antigen (PSA). The fabricated immunosensor successfully detected PSA concentrations ranging from 0.05 to 60 ng/mL, with a detection limit of 0.01 ng/mL, showcasing high sensitivity comparable to other existing methods. This research provides a versatile and promising platform for developing advanced biosensors for disease diagnostics and further expanding the application of MOFs.