Surface Plasmon Resonance Characteristics of Au Nanoparticles Layered Sensor Chip for Direct Detection of Stress Hormone Conjugated by Nanoparticles

In this study, localized surface plasmon resonance (LSPR) effect was characterized for immuneassay to detect cortisol conjugated nanoparticles (NPs) using a cuvette-compatible Au NPs layered sensor chip. A neuro stress hormone, cortisol, as target molecule was conjugated to 2 nm, 5 nm, 30 nm, and 40 nm Au NPs or 14 nm zinc oxide (ZnO) NPs to enhance the LSPR detection signals as plasmonic coupling elements with respect to cortisol monoclonal antibody (c-Mab) of probe molecule, which was immobilized on the Au NPs layered sensor. The cortisol conjugated 2 nm and 5 nm Au NPs and 14 nm ZnO NPs, which were selectively immune- bound to the c-Mab coated Au NPs sensor, showed LSPR effects to induce absorbance increases under UV-Vis spectroscopy. Also, the cortisol conjugated 2 nm, 5 nm, 30 nm and 40 nm Au NPs could show disparate plasmonic coupling effects to shift maximum absorbance wavelength peaks. Even though the cortisol conjugated 14 nm ZnO NPs could show increased absorbance only, the conjugation of cortisol to both Au and ZnO NPs was proved to enhance direct LSPR detection of the cortisol, which could not be explicitly sensed by itself for direct LSPR signal.