Hybrid biosensing systems for the detection of biomolecules and disease biomarkers
Optical metasurfaces are configurations of artificially structured surfaces designed to obtain unusual electromagnetic properties. The ability to manipulate a confined electromagnetic field enables metasurfaces to be utilized as optical point-of-care (POC) biosensors for the detection of low concentrations of biomarkers. Moreover, the integration of fluorescent molecules and plasmonic metasurfaces is utilized to enhance both plasmonic and fluorescent signals; however, the nanoscale distance and spectral overlap between the fluorescent emitter and plasmonic metasurface are crucial for the separation of the fluorescence-coupled plasmonic radiation and non-radiative induced plasmon surface entrapment. In this study, fluorescently labeled (FITC) proteins are integrated over a plasmonic metasurface via three different surface modifications for obtaining a hybrid biosensing system that boosts the device’s plasmonic sensitivity and lowers the detection limit. The metasurface is fabricated via physical vapor deposition of titanium (10 nm), silver (30 nm), and gold (15 nm), respectively over polycarbonate nanograting substrates of optical disks (DVDs). Additionally, the surface modifications are arranged via short-distance, medium-distance, and long-distance modifications for fluorescently labeled molecule binding. After the evaluations, the highest plasmonic wavelength shift over the FITC labeled protein binding is obtained from the medium-distance modification with ~4.4 times signal enhancement over the short-distance modification. The medium-distance modification is further combined with an immunoassay for the detection of Alzheimer’s disease. Consequently, this study paves the way for designing new arrangements on a metasurface to couple with fluorescence molecules while enhancing the analytical performance of the plasmonic biosensor.