Porous platinum nanozyme-amplified capacitance immunoassay for alpha-fetoprotein with hepatocellular carcinoma on an interdigitated gold micro-comb array.

Background: Hepatocellular carcinoma, one of the most common malignancies, is the worldwide three cause leading the mortality of cancers. Alpha-fetoprotein (AFP) is a typical tumor marker for the recurrences of HCC, and can be utilized potentially during routine follow-up after HCC resection. Therefore, sensitive and accuracy detection of AFP is very critical at the early stage of hepatocellular carcinoma.

Results: In this work, an in-situ amplified capacitance immunoassay was designed for highly sensitive determination of AFP in biological fluids. The capacitance immunosensor was fabricated by means of immobilizing anti-AFP capture antibodies on an interdigitated gold micro-comb array through a carbodiimide coupling method. Porous platinum nanoparticles (PtNPs) were used for the labeling of anti-AFP detection antibody. The presence of target analyte induced the formation of the sandwiched immunocomplex between capture antibody and detection antibody. The carried porous PtNPs with peroxidase-like activity catalyzed 4-chloro-1-naphethol oxidation to produce an insoluble benzo-4-chlorohexadienone precipitation in the presence of hydrogen peroxide. The precipitation was coated on the micro-comb electrode, thus causing the capacitance change. Two labeling protocols including porous PtNPs and solid PtNPs were investigated for determination of AFP, and improved analytical features were acquired with porous PtNPs. Under optimal conditions, porous PtNP-based capacitance immunoassay gave a good linear response from 0.01 ng mL to 300 ng mL AFP with a detection limit of 7.4 pg mL. Good reproducibility, high specificity and long-term stability were also achieved. In addition, 15 human serum specimens were determined through our method, and the results were in accordance with those obtained from commercial AFP enzyme-linked immunosorbent assay.

Significance: This capacitance immunoassay offers promise for sensitive and cost-effective detection of cancer biomarkers without the requirement of natural enzymes. Importantly, porous PtNP-based labeling strategy opens a new horizon for advanced development of capacitance immunoassays.