Silver amplified enzyme-free colorimetric immunoassay via graphene oxide as AgNPs carrier for sensitive detection of cancer biomarker

Highly sensitive and low-cost detection methods of cancer biomarker are very important for the early screening of cancer. In this contribution, a novel enzyme-free colorimetric immunoassay for sensitive and simple detection of alpha-fetoprotein (AFP) was developed based on the silver amplified strategy via graphene oxide (GO) as AgNPs carrier. AgNPs deposited on the surface of GO to form GO-AgNPs nanocomposites. GO-AgNPs nanocomposites were linked with detection antibody of AFP and quantitatively introduced by AFP through specific reaction between antigen and antibody. In the presence of H 2 O 2 , AgNPs dissolved and released Ag + . Ag + can promote coupling of 2,4-dichlorophenol with 4-aminoantipyrine to yield quinoneimine dye, by measuring the absorbance of the quinoneimine dye enzyme-free colorimetric immunoassay of AFP was established. The large surface area of GO can increase the introduction of AgNPs and greatly amplify the detection signal. The enzyme-free colorimetric immunoassay in this work with the advantages of cost effective, rapid detection and high sensitivity, and possesses excellent analytical performance of AFP in the range from 5 ng mL −1 to 200 ng mL −1 with a limit of detection of 0.19 ng mL −1 (3σ/k, n = 10). The results of human serum samples performance satisfactory, which demonstrated good application values for point of care testing (POCT) in clinical diagnosis.