An opto-fluidic ring resonator biosensor for the detection of organophosphorus pesticides

We developed a novel label-free opto-fluidic ring resonator (OFRR) biosensor for detection of an organophosphorus (OP) pesticide. The OFRR is based on a micro-sized glass capillary whose circular wall forms a ring resonator that supports the whispering gallery modes (WGMs). The WGMs has an evanescent field in the capillary core and interacts with the analyte flowing in the capillary. We used parathion-methyl as a model system to investigate the OFRR sensing performance in terms of bulk refractive index sensitivity, surface activation for affinity property, detection limit, and reproducibility. The performance of the OFRR was further compared with that of the Biacore 3000 SPR system. Our results show that the detection limit of 3.8 × 10−11 M for parathion-methyl was achieved with an analysis time of about 0.5 min, 10 times faster than the surface plasmon resonance (SPR) system. Furthermore, the OFRR biosensor demonstrated excellent reproducibility (R.S.D. = 3.5%, n = 5). The OFRR offers optical label-free detection mechanism with integrated microfluidics. It is a promising technology platform for development of portable multi-channel biosensors with high sensitivity, quick detection time, and sub-nanoliter detection volume.