Chiroplasmonic assemblies of gold nanoparticles as a novel method for sensitive detection of alpha-fetoprotein

Abstract

Serum alpha-fetoprotein (AFP) is present in enhanced concentrations in patients with liver cancer. Thus, sensitive detection of AFP plays an important role in the early diagnosis and treatment of cancer. In this study, a novel chiroplasmonic assay is presented for the determination of AFP. It is based on (a) the use of DNA-induced chiroplasmonic assemblies of gold nanoparticles (AuNPs) and (b) the high specificity and affinity constants between AFP and its aptamer. First, the AFP aptamer is hybridized with its complementary sequence immobilized on AuNP. As a result, the DNA-modified AuNPs are assembled to form AuNPs dimers which display strong chiroptical activity. If, however, AFP is added, it will bind to the aptamer and this results in a destruction of the aptamer-DNA hybrid and a reduction of the CD signal. Under optimized conditions, the CD intensity drops linearly with the log of the concentration of AFP in the range from 0.02 to 5 ng⋅mL−1. Compared to the established method, this assay does not require bisulfite conversion, PCR amplification or separation. Amounts as low as 11 pg⋅mL−1 (S/N = 3) AFP can be detected. The method was applied to spiked human serum samples and gave recoveries ranging from 92.0% to 106%, and the relative standard derivations ranged from 4.6% to 6.3%. To the best of our knowledge, this is the first chirality based assay for AFP.