Fe3O4@Au nanoparticles as a means of signal enhancement in surface plasmon resonance spectroscopy for thrombin detection

Abstract The core-shell gold capped magnetic nanoparticles (GMPs) have been receiving increasing attention because of its optical and magnetic properties. In order to evaluate the ability of GMPs as a means of signal enhancement in surface plasmon resonance (SPR) spectroscopy, a sandwich SPR sensor is constructed by using thrombin as a model analyte. In this design, thrombin is captured by thrombin aptamer 1 (Apt1) and sensitively detected through addition of GMPs-Apt2 conjugates. Compared with gold nanoparticles (GNPs) and magnetic nanoparticles (MNPs), GMPs-Apt2 conjugates result in a significant SPR angle increase, which is mainly attributed by the larger mass and higher refractive index of the GMP nanoparticles. Therefore, the detection limit can be achieved as low as 0.1 nM. Since GMP may have high stability and biocompatibility, it can be a useful sandwich element for sensor fabrication and an excellent amplification reagent for SPR measurement. This work may also afford a new model to improve the sensitivity and selectivity of SPR biosensors in protein detection and disease diagnosis.