Line-scanning detection instrument for photonic crystal enhanced fluorescence.

A laser line-scanning instrument was developed to optimize the near-field enhancement capability of a one-dimensional photonic crystal (PC) for excitation of surface-bound fluorophores. The excitation laser beam is shaped into an 8 μm × 1 mm line that is focused along the direction of the PC grating, while remaining collimated perpendicular to the grating. Such a beam configuration offers high excitation power density while simultaneously providing high resonant coupling efficiency from the laser to the PC surface. Using a panel of 21 immunofluorescence assays on the PC surface in a microarray format, the approach achieves an enhancement factor as high as 90-fold between on-resonance and off-resonance illumination. The instrument provides a capability for sensitive and inexpensive analysis of cancer biomarkers in clinical applications.