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 H2O2, 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 (3 sigma/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.