A strategy for signal amplification using an amperometric enzyme immunosensor based on HRP modified platinum nanoparticles

Abstract

A novel sandwich-type electrochemical enzyme immunosensor for sensitive detection of α-1-fetoprotein (AFP) using a signal amplification strategy based on the enzyme and the catalytic activity of Pt nanoparticles (PtNPs) is investigated in this work. Sensitivity was greatly amplified by the detection mode which was based on dual signal amplification: (1) secondary antibody labeled HRP-functionalized PtNPs were introduced on the electrode surface through biotin–avidin interactions; (2) the biotin-labeled HRP was further attached to HRP-functionalized PtNPs to assemble a dense HRP film, which resulted in significant enhancement of the current response. The adjusted (but not random) orientation of anti-AFP on the nanohybrid film of gold nanoparticles/multi-walled carbon nanotubes (AuNP/MWNT) was accomplished using an avidin–biotin immobilization technique. The nanohybrid film AuNP/MWNT can improve the response of the immunosensors due to its higher exposed surface area, high catalytic activity which facilitates electron transfer and excellent biocompatibility. The performance of the amperometric immunosensor was evaluated and optimized for best performance. The detection limit for AFP was found to be 0.08 ng/mL at S/ N = 3 and the detection concentration were in the range between 0.25 and 100 ng/mL.