Self-referencing a single waveguide grating sensor in a micron-sized deep flow chamber for label-free biomolecular binding assays

Abstract

In order to allow the design of increasingly sensitive label-free biosensors, compensation of environmental fluctuations is emerging as the dominant hurdle. The system and technique presented here utilize a unique combination of microfluidics, optical instrumentation, and image processing to provide a reference signal for each label-free biomolecular binding assay. Moreover, this reference signal is generated from the same sensor used to detect the biomolecular binding events. In this manner, the reference signal and the binding signal share nearly all common-mode noise sources (temperature, pressure, vibration, etc.) and their subtraction leaves the purest binding signal possible. Computational fluid dynamic simulations have been used to validate the flow behavior and thermal characteristics of the fluids inside the sensing region. This system has been demonstrated in simple bulk refractive index tests, as well as small molecule (biotin/streptavidin) binding experiments. The ability to perform not only simple binding but also control experiments has been discussed, indicating the wide applicability of the technique.

Wavelength interrogation of grating-based optical biosensors in the input coupler configuration

“…A variety of other clever schemes has been proposed to couple light into the waveguide with a simplified device fabrication, e.g. using a line illumination instead of a spot illumination to generate many angles [26] or chirped grating couplers [27]. In the output grating coupler, as well as in approaches exploiting grating couplers in reflection configuration [5,28], the sensor response improves the farther the detector is placed, limiting the miniaturization of the system and requiring a vibration-free operation environment.…”

Optofluidic integration for microanalysis

“…Yuen et al (2005) realised a polymer H-shaped microfluidic device integrated with a grating for sensing, in which a reference fluid and analyte fluid could be passed over the grating under the same conditions and measured simultaneously. Laser light is incident through a polariser and focused via a lens to provide many angles to couple into the grating.…”

Lipid-Sensing High-Throughput ApoA-I Assays

“…S2A). 24 For the label-free assay, we also used recombinant N8H-Avi-ApoA-I(E136C) protein in the presence or absence of lipids. To capture biotinylated N8H-Avi-ApoA-I(E136C), we coated the Epic microplate with either streptavidin (50 µg/mL) or BSA (40 µg/mL), which resulted in an immobilized surface density of ~1600 pm (data not shown).…”