Sensitive detection of interleukin-6 on a plasmonic chip by grating-coupled surface-plasmon-field-enhanced fluorescence imaging

A plasmonic chip, which is a grating substrate coated with metal films, was fabricated and applied to grating-coupled surface-plasmon-field-enhanced fluorescence imaging (GC-SPFI). With the enhanced fluorescence excited by the surface plasmon field on the plasmonic chip, interleukin-6 (IL-6), a marker protein of lifestyle-related diseases, was measured using a sandwich assay system. IL-6 was quantitatively determined to be up to 2 pg/mL by GC-SPFI. The detection sensitivity for IL-6 was superior to that with an enzyme-linked immunosorbent assay, and GC-SPFI was shown to be a valid method for immunosensing.