Surface plasmon-coupled emission (SPCE)-based immunoassay using a novel paraboloid array biochip.

We have carried out a human IgG immunoassay on a novel disposable optical array biochip using surface plasmon-coupled emission (SPCE) detection. The work successfully combines the advantages of the highly directional SPCE emission profile and enhanced surface plasmon excitation with the high light collection efficiency achieved using supercritical angle fluorescence (SAF). This is achieved using an array of transparent paraboloid polymer elements which have been coated with a thin gold layer to facilitate SPCE. Moreover, since only the emission of molecules which are close to the metal surface couple into the surface plasmon, the detection is highly surface-specific leading to background suppression and increased signal-to-noise ratio. Theoretical calculations have been carried out in order to match the surface plasmon resonance angles and SPCE emission angles to the paraboloid array features for light collection. A sandwich assay format was used and a dose response curve was obtained in the concentration range 2 ng/ml to 200 microg/ml yielding a limit of detection of 20 ng/ml. This is the first demonstration of an SPCE-based assay on a disposable biochip platform and indicates the potential of SPCE-based arrays for high-throughput analysis of biomolecular interactions.