New Sensitive Biosensor Platform by Plasmon Field Enhanced Photoreaction and Fluorescence

We used the plasmon-enhanced electric field not only as an excitation enhancement field for fluorescence but also as a photochemical reaction field, aiming to create a biosensor platform with highly sensitive detection in the area spatially controlled. The plasmonic chip used has a bull's eye structure with a pitch of 480 nm coated with silver and silica layers, composed of 2000 bull's-eye patterns array. 3-((2-formyl-3-methylphenyl) thio)propanoic acid (O-MBA) was modified on the aminated surface of the plasmonic chip and after exposure to UV light, the intermediates of O-MBA reacted with biotin-maleimide (Biotin-M). Cy5Streptavidin (Cy5-SA) was added to biotinylated surface as a detection target and detected with transmitted-type fluorescence microscope. A bright fluorescence image was obtained in the Bull's eye pattern within the UV-irradiated spot. This is due to the fluorescence enhancement effect in the Bull's eye pattern and the higher density of binding site by the enhanced photochemical reaction of O-MBA. The calibration curve of fluorescence intensity against the Cy5-SA concentration show that a highly sensitive biosensor platform was constructed by promoting photochemical reactions and enhancing fluorescence.