Abstract
We have demonstrated real-time, label-free detection of small molecule binding using a novel optical biosensor. This
sensor is a recently developed sensing platform incorporating a one-dimensional photonic crystal (PC) structure in a
total-internal-reflection (TIR) geometry (PC-TIR). This simple configuration functions as an open Fabry-Perot resonator
which provides a narrow optical resonance to enable label-free, highly sensitive detection of analyte molecules on the
sensing surface in the enhanced evanescent field. Moreover, when the differential intensity modulation during binding is
measured, a very high detection sensitivity can be obtained, and real-time binding observed. The well-studied biotinstreptavidin
system was chosen to calibrate the detection limit for small molecule detection. Effective surface
functionalization methods for streptavidin immobilization on the silica sensing surface were investigated, and analyte
biotin molecules specifically binding to the sensing surface were monitored in real time. The binding of the smallest
molecule D-Biotin, with a molecular weight of 244 Da, was easily experimentally observed with a high signal to noise
ratio, which shows that the PC-TIR sensor has great potential to be a high-sensitivity and high-throughput sensing
technology for small molecule binding analysis.
