Single-layer graphene-coated gold chip for enhanced SPR imaging immunoassay

Surface plasmon resonance imaging (SPRi) is a powerful tool for label-free, real-time and high-throughput immunoassay, but its sensitivity needs essential improvement. It has been recently reported that the sensitivity of angular-interrogation surface plasmon resonance (SPR) could be efficiently enhanced on single-layer graphene-coated gold chip. The usefulness of this method however remains unclear for reflectivity-based SPRi platform. Herein for the first time we demonstrate that the graphene coating-enabled intrinsic sensitivity enhancement is applicable to high-throughput SPRi and the enhancement factor is further quantitatively evaluated. High-quality single-layer graphene is transferred in a site-controllable manner to cover half of spots on the SPRi gold array chip. With anti-zearalenone (ZEN) antibody as a model target and polydopamine (PDA) thin film as a reactive layer for probe immobilization, the SPRi detection signals on two types of sensing spots are quantitatively compared on a single chip and the enhancement factor is evaluated. It is unambiguously disclosed that on the reflectivity-based SPRi platform, single-layer graphene coating results in a ca. 40% enhancement on the detection signal (reflectivity increase, AR). This work unveils the compelling SPRi sensitivity enhancement of graphene coating and may facilitate its broad practical applications.