Sensitive fluorescence immunoassay of alpha-fetoprotein through copper ions modulated growth of quantum dots in-situ

A novel fluorescence immunoassay has been developed for alpha-fetoprotein (AFP) detection based on copper ions (Cu2+) regulated formation of quantum dots in situ. In place of traditionally used fluorophore or enzyme for signal amplification, CuO nanoparticles (NPs) were used as signal amplifier to enhance the detection sensitivity. In the presence of AFP, CuO NPs-labeled antibody can be specifically captured through the sandwich-type immunoreaction. By the use of L-cysteine (Cys) as stabilizer, aqueous fluorescent CdS quantum dots (QDs) can be formed by a facile synthesis method. After acid dissolution, numerous Cu2+ ions were released from the CuO NPs, which can act as catalyst to catalyze the oxidization of Cys and thus greatly reduce the amount of CdS QDs formed. The fluorescence intensity showed a good linear relationship with the AFP concentration in the range from 1 to 80 ng/mL, as low as 0.45 ng/mL AFP can be detected. The high throughput, disposability, sensitivity and accuracy of the proposed fluorescence immunoassay showed good applicability in clinical diagnosis. (C) 2017 Elsevier B.V. All rights reserved.