Use of Microring Resonators for biospecific interaction analysis

Integrated optical biosensors based on Mach-Zehnder Interferometers and Microring Resonators are widely used for food/drug monitoring and protein studies thank to their high intrinsic sensitivity, easy integration and miniaturization, and low cost.(1,2) In this study, we present a system to perform antibody interaction analysis using a photonic chip made of an array of six microring resonators (MRRs) based on the TriPleX platform. A compact system is presented where the input light is provided by a Vertical Cavity Surface Emitting Laser (VCSEL) pigtailed to a single mode fiber and operating at a approximate to 850nm wavelength. The output signal is detected by PIN photodetectors placed in the optical signal read-out module (the so-called OSROM) and processed by an easy-to-use Fourier Transform algorithm. Bulk sensitivity (S-b=98 +/- 2.1 nm/RIU) and Limit of Detection (LOD=(7.5 +/- 0.5) x10(-6) RIU) are measured and appeared to be very similar for the six MRRs on the same chip,(3) which is an important property for multianalyte detection. An analysis of the anti-biotin interaction with immobilized biotin is performed by using different concentrations of anti-biotin antibody. The dependence of the resonance wavelength shift from the antibody concentration, as well as the association and the dissociation rate constants are calculated. For the average dissociation constant (K-D) of anti-biotin antibody toward immobilized biotin, a value of (1.9 +/- 0.5) x 10(-7) M is estimated, which is of the same order of magnitude of other published data.(4) Furthermore, the specificity of the interaction is confirmed by using negative control antibodies and by performing competition with free, i.e., dissolved, biotin. In addition, the functional surface of the sensors could be regenerated for repeated measurements up to eight times by using 10 mM glycine/HCl pH 1.5.