Transmission SPR of Gold Nanoslit Array and Ultrasensitive Detection of a Retinol Binding Protein

Retinal-modified SAM-coated nanoslit array thin gold film was used for ultra-sensitive (picomolar) detection of a ligand protein (β-Lactoglobulin) with a transmission SPR mode. The transmission spectra of nanoslit arrays with varying periods were evaluated for nanostructure optimization with respect to primary peak position, shape and sensitivity. Sensitivity of this method, as measured in water, was estimated at 3 ng/mL, or approximately 130 picomolar. Additionally a monotonic shift in primary peak wavelength was observed with changing nanoslit periodicity. This type of in-plane nanoarray chip is currently being integrated with microfluidic platforms for chemical and/or biological sensing applications.