Magnetic Nanoparticle-Based Nano-Grating Guided-Mode Resonance Biosensors

Biomolecular detection systems based on monitoring changes in the refractive indices of functionalized surfaces are promising for applications as chemical and biological sensors. Here, we describe the design and figures of merit of our refractive index-based guided-mode resonance (GR) biosensor consisting of thin film silicon nitride sub-wavelength nano-gratings. The sensitivity of our nano-grating GR sensor was experimentally determined to be 59.3 nm per refractive index unit. We describe how the wavelength for maximum intensity of diffraction (peak wavelength) of nano-gratings was affected when functionalized magnetic nanoparticles (MNPs) were attached onto GR sensor surfaces. Moreover, we demonstrate with avidin-biotin model experiments that attaching MNPs to sensor surfaces enhances the dynamic range of detection of the GR system detection. The peak wavelength value (PWV) shifted by 0.35 nm in the case of avidin with a concentration of avidin 400 nmol/L immobilized on the sensor surface. In contrast, we achieved a 1.41 nm PWV shift after adding 5% MNPs to the solution of avidin. Not only did the MNPs enhance the dynamic range of detection, but also magnetically induced interaction of avidin-biotin significantly reduced the detection time.