Abstract
Prostate-specific antigen (PSA) was used as the model, an ultrasensitive label-free electrochemiluminescent immunosensor was developed based on graphene quantum dots. Au/Ag-rGO was sythsized and used as electrode material to load a great deal of graphene quantum dots due to the large surface area and excellent electron conductivity. After aminated graphene quantum dots and acarboxyl graphene quantum dots were modified onto the electrode, the ECL intensity was much high using K2S2O8 as coreactant. Then, antibody of PSA was immobilized on the surface of modified electrode surface through the adsorption of Au/Ag toward proteins, leading to the decrease of the ECL intensity. As proven by ECL spectra test and electrochemical impedance spectroscopy (EIS) analysis, the fabrication process of the immunosensor is successful. Under the optimal conditions, the ECL intensity decreased linearly with the logarithm of PSA concentration in the range of 1 pg/mL ~ 10 ng/mL. The detection limit achieved is 0.29 pg/mL. The immunosensor results were validated through the detection of PSA in serum samples with satisfactory results. Due to excellent stability, high sensitivity, acceptable repeatability and selectivity, the immunosensor has promising applications in disease and drug analysis.
Highlights
Prostate-specific antigen (PSA) was used as the model, an ultrasensitive label-free electrochemiluminescent immunosensor was developed based on graphene quantum dots
Antibody of PSA was immobilized on the surface of modified electrode surface through the adsorption of Au/Ag toward proteins, leading to the decrease of the ECL intensity
Au/Ag-rGO was used as electrode material to load a great deal of graphene quantum dots due to the large surface area and excellent electron conductivity
Summary
A gradual decrease in the ECL signal was achieved when PSA antibody (curve c), BSA (curve d) and PSA (curve e) was modified onto the electrode surface successively, which could be attributed to the block of biomacromolecules hindering the electron transfer. Both the above results were consistent with the fact that the electrode was modified as expected. Compared with the bare electrode (curve a), the ECL response was enhanced after GCE was modified. The ECL responses were measured by mixing 5 ng/mL of PSA with 100 ng/mL carcinoembryonic antigen (CEA), 100 ng/mL BSA and 100 ng/mL glucose,
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