Signal Enhancement of Surface Plasmon Resonance Based Immunosensor Using Gold Nanoparticle-Anti body Complex for β-Amyloid (1-40) Detection

Numerous studies have indentified that beta-amyloid (1-40) in cerebrospinal fluid as a potential biomarker for Alzheimer's disease. In order for early detection of the Alzheimer's disease, an ultrasensitive diagnostic tool is required. In this study, an ultrasensitive surface plasmon resonance (SPR) based immunosensor for beta-amyloid (1-40) was developed and its signal enhanced (1-40) with a gold (Au) nanoparticle-antibody complex. Antibodies to beta-amyloid (1-40) were immobilized on the Au surface leading to a highly efficient immunoreaction due to the fact the paratope of the antibody faced in the opposite direction to the solid surface. The surface morphology of the biosurface was investigated by using scanning tunneling microscopy (STM). The binding process of antibody fragments to the Au surface, target analytes, and Au nanoparticle-antibody complexes were monitored using SPR. The plot of SPR angle difference versus beta-amyloid (1 -40) concentration shows a linear correlation over a concentration range of nine orders of magnitude, having a deletion limit up to 1 fg/ml.