Facile synthesis of Cu2O@TiO2-PtCu nanocomposites as signal amplification strategy for the insulin detection.

A novel ultrasensitive sandwich-type electrochemical immunosensor was proposed for the quantitative detection of insulin, a representative biomarker for diabetes. To this end, molybdenum disulfide nanosheets loaded gold nanoparticles (MoS2/Au NPs) were used as substrates to modify bare glassy carbon electrodes (GCE). The MoS2/Au NPs not only present superior biocompatible and large specific surface area to enhance the loading capacity of primary antibody (Ab1), but also present good electrical conductivity to accelerate electron transfer rate. Moreover, the amino functionalized cuprous oxide @ titanium dioxide octahedral composites (Cu2O@TiO2-NH2) were prepared to load dendritic platinum-copper nanoparticles (PtCu NPs) to realize signal amplification strategy. The resultant nanocomposites (cuprous oxide @ titanium dioxide octahedral loaded dendritic platinum-copper nanoparticles) demonstrate uniform octahedral morphology and size, which effectively increases the catalytically active sites and specific surface area to load the secondary antibody (Ab2), even increases conductivity. Most importantly, the resultant nanocomposites possess superior electrocatalytic activity for hydrogen peroxide (H2O2) reduction, which present the signal amplification strategy. Under the optimal conditions, the proposed immunosensor exhibited a linear relationship between logarithm of insulin antigen concentration and amperometric response within a broad range from 0.1 pg/mL to 100 ng/mL, and a limit detection of 0.024 pg/mL. Meanwhile, the immunosensor was employed to detect insulin in human serum with satisfactory results. Furthermore, it also presents good reproducibility, selectivity and stability, which exhibits broad application prospects in biometric analysis.