Characterization of grating couplers for affinity-based pesticide sensing

Abstract

The reflection grating coupler for direct affinity sensing is characterized in detail. The performance of this device and its potential in affinity sensing application are investigated with two affinity-based systems: A self-assembling protein-multilayer system based on avidin-biotin interaction was used to compare the response of the device with theoretical expectations. The analytical performance was characterized by a pesticide immunoassay carried out in an indirect test format with a covalently immobilized triazine derivative. Experimentally determined parameters were in good agreement with model calculations. During the binding of 12 protein monolayers at the surface, the change in effective refractive index Dn(eff) detected for a single layer decreased from approximately 8 x 10(-4) to less than 4 x10(-5) by more than 95%, indicating a filling of the evanescent field. By comparison with bulk refractive-index measurements, a refractive index n(D) approximately 1.38 of the protein multilayer was estimated. Fitting of the model gave a refractive index n(D) = 1.377 of the protein multilayer and an average thickness of 11 nm for a single protein layer. An average noise of Dn(eff) = 8.5 x 10(-7) was detected, corresponding to approximately 1% of the maximum response for a protein monolayer. At a triazine derivative attached to the surface through dextran-based surface chemistry, a maximum antibody loading that corresponds to an Dn(eff) of 1.5 x 10(-3) was observed. In an indirect immunoassay of the herbicide simazine, a detection limit of 0.25 mug/1 of simazine was reached with polyclonal Fab fragments in a concentration of 1 mug/ml.

Interferometric biosensor based on planar optical waveguide sensor chips for label-free detection of surface bound bioreactions

“…A review on various application fields of label free optical biosensors in drug discovery can be found in Cooper (2002). Among these techniques are biosensors based on surface plasmon resonance (Green et al, 2000;Karlsson, 2004), reflectometric interference spectroscopy (Hänel and Gauglitz, 2002), grating couplers (Piehler et al, 1997;Cottier et al, 2003) and interferometric devices (Brandenburg et al, 2000;Prieto et al, 2001;Campbell et al, 1998;Ymeti et al, 2005;Cross et al, 2003).…”

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

“…The grating coupler has been implemented in a variety of configurations: input, output, and reflective modes [4][5][6][7] as well as various resonance approaches [8][9][10]. The operating principle of the input grating coupler is shown in Fig.…”

Simply Modified Biosensor for the Detection of Human IgG Based on Protein AModified Porous Silicon Interferometer

“…[1][2][3][4][5] The PSi optical sensing features were based on the changes of its photonic properties, such as photoluminescence or reflectance, on exposure to the gaseous or liquid substances. [6][7] Two main optical transduction methods for label-free biosensors were both optical interferometric methods based on interferometers, 8 evanescent wave devices, 9 and grating couplers, 10 and surface plasmon methods based on metal films, 11 and colloids. 12 However they required a tedious work and very complex preparation during analysis.…”