Construction of electrochemical immunosensor by integrating N, S doped carbon dots with FeO for ultrasensitive sensing alpha-fetoprotein.

As a vital biomarker, alpha-fetoprotein (AFP) is closely associated with hepatocellular carcinoma (HCC), whose ultrasensitive determination is essential to early diagnosis of HCC and sequential reduction of morbidity and mortality. Especially, the quantitative detection of AFP with high accuracy and ultra-sensitivity and overcoming the high complexity and cost is of great importance in clinical HCC diagnosis and curative effect evaluation. Herein, an electrochemical immunosensor was constructed by integrating NS-doped carbon dots (NS-CDs) with FeO (FeO@NS-CDs) for the quantitative analysis of AFP. The NS-CDs offered the advantages of good biocompatibility, being rich in functional groups, especially unreduced -COOH, and a large specific surface area, leading to a large number of active sites with good AFP anchoring ability. Owning good electrical conductivity of FeO, the synergistic and electronic effects were achieved by integrating with NS-CDs, which promoted the electron transfer on the surface of the electrode, facilitated capturing antibodies, and generated effective electrochemical signals. Under optimal conditions, the electrochemical immunosensor displayed an ultra-low detection limit (16.8 fg mL) in a broad range of 5-1 × 10 pg mL. The detection performance of the sensor was improved more than 2 times by integrating NS-CDs, with outstanding selectivity, repeatability, reproducibility, and stability. This study provides some constructive insights for the development of promising nanomaterials and methods to promote progress in early diagnostics.