Alpha-methylacyl-CoA racemase (AMACR) is over-expressed in many
cancer types and can serve as a novel diagnostic
biomarker. Development of convenient and sensitive detection methods of AMACR is of particular importance for
cancer diagnosis. Aptamers are a type of recognition elements, which possess many advantages over antibody, making them suitable for applications in biosensing and biotechnology. In this work, we use the efficient surface modification of
gold nanoparticles (AuNPs) to prepare the
horseradish peroxidase (HRP) and aptamer dual-functionalized nanoprobe. The immobilization of HRP and
thiol-terminated aptamer on the surface of AuNPs can be achieved through electrostatic interaction and the formation of Au-S bond, respectively. This nanoprobe, which is used as discriminating and catalytic probe, can be combined with
enzyme immunoassay method to increase the detection sensitivity of AMACR. The detection limit can reach as low as 4.6 pg mL(-1) due to the dual signal amplification from enzymatic cycling and the high loading of
enzymes on AuNPs. This sensitivity is about three orders of magnitude higher than that of AMACR aptamer based fluorescence method, which is also comparable to or one order of magnitude higher than that of ELISA. Furthermore, this method is more simple and effective, which not only avoids the conjugation between recognition
element and the catalytic
enzyme, but also achieves greater signal amplification. This assay could be used as a sensitive and selective platform for the detection of target
protein.