摘要
An ultrasensitive sandwich-type amperometric immunosensor for the detection of cancer biomarker, α-fetoprotein (AFP), was fabricated using Au/chitosan modified glassy carbon electrode (GCE) and antibody-functionalized dumbbell-like Au-Fe 3 O 4 heterostructures as sensing platform and immuno-labels, respectively. The sensing platform was constructed by modifying GCE surface with chitosan and Au nanoparticles (NPs) for effective immobilization of primary antibody (Ab 1 ). To fabricate the labels, nano-Au NPs were first epitaxially growth onto Fe 3 O 4 surface to form the dumbbell-like Au-Fe 3 O 4 followed by conjugation of secondary antibody (Ab 2 ) onto Au surface (Au-Fe 3 O 4 -Ab 2 ). Results showed that the GCE modified with chitosan produced high electrochemical response by conjugation of more Au-Ab 1 and the dumbbell-like Au-Fe 3 O 4 served as a dual-probe to immobilize Ab 2 onto Au as well as to reduce H 2 O 2 by Fe 3 O 4 , resulting in enhancement of signal amplification. Under the optimal condition at pH 6.5 and 30 C, the prepared Au-Fe 3 O 4 /Ab 2 /AFP/Ab 1 /Au/chitosan/GCE immunosensors exhibited a good analytical performance in the presence of 10 mM H 2 O 2 with wide dynamic range of 4 orders of magnitude (0.01-40 ng mL -1 ) and low detection limit of 2.3 pg mL -1 . In addition, the proposed immunoassay also displayed good reproducibility and storage stability. Results obtained in this study clearly demonstrate that the Au-Fe 3 O 4 /Ab 2 /AFP/Ab 1 /Au/chitosan/GCE immunosensor is a promising biosensing platform for highly sensitive detection of AFP and various tumor makers. © 2013 Elsevier B.V.