Photonic wire biosensor microarray chip and instrumentation: application to serotyping of Escherichia coli isolates

S. Janz, D.-X. Xu, M. Vachon, N. Sabourin, P. Cheben, H. McIntosh, H. Ding, S. Wang, J.H. Schmid, A. Delâge, J. Lapointe, A. Densmore, R. Ma, W. Sinclair, S.M. Logan, R. MacKenzie, Q.Y. Liu, D. Zhang, G. Lopinski, O. Mozenson, M. Gilmour, H. Tabor
National Research Council, Canada, CA

Keywords: microarry, biosensor

Summary:

This presentation will give an overview the use of silicon photonic wire waveguides as molecular binding sensors. Photonic wires waveguides are strands silicon approximately 220 nm thick and less than 500 nm wide that can be used to build an optical circuit on a silicon chip. Due to their small size and high refractive index, the light propagating through photonic wires is strongly coupled to molecules binding to the silicon surface. Hence these structures can be used to build sensors that may be addressed and interrogated using well established methods adapted from integrated optics. In particular, the photonic wire molecular biosensor microarray chip architecture and supporting instrumentation recently developed at the National Research Council Canada will be described. Silicon microarray chips with 16 and 128 independent sensors have been demonstrated, where each sensor can provide an independent molecular binding curve. The individual sensors are 50 μm diameter structures consisting of a long closed loop of silicon photonic wire waveguide folded into a spiral to form a ring resonator. An array of 128 such sensors occupies a 2×2 mm2 area on a silicon chip. Microfluidic sample delivery channels are fabricated monolithically on the chip. The size and layout of the sensor array is fully compatible with commercial spotting tools designed to independently functionalize fluorescence based biochips. The sensor chips are interrogated using an instrument that delivers sample fluid to the chip and is capable of acquiring up to 128 optical sensor outputs simultaneously and in real time. Coupling light from the sensor chip is accomplished through arrays of sub-wavelength surface grating couplers, and the signals are collected in parallel by a fixed two-dimensional detector array. The chip and instrument are designed so that connection of the fluid delivery system and optical alignment are automated, and can be completed in a few seconds with no active user input. This microarray system is used to demonstrate a multiplexed assay for serotyping E. coli bacteria using serospecific antibody probe molecules. The goal of this work is to develop a multiplexed microarray approach to identifying pathogenic E. coli bacteria serotypes that is more quantitative and faster than established methods such as agglutination tests. Being a microfluidic based technology, this method should also consume much smaller volumes of valuable serospecific antibodies developed for this purpose.