PLANAR WAVEGUIDES FOR FLUORESCENCE BIOSENSORS

doi:10.1016/B978-044453125-4.50005-X

Optical Biosensors (Second Edition)

Today and Tomorrow

2008, Pages 139-184

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Biosensors consist of two important features: the molecular recognition element and the signal transduction mechanism. The leading methods for fluorescence-based, multianalyte detection are based on total internal reflection fluorescence (TIRF). TIRF excitation of planar waveguides is the most utilized optical configuration. Immobilization of multiple capture biomolecules on planar waveguides provides for multianalyte detection on a single substrate. TIRF is a means of selectively exciting the fluorescence emission of fluorophores present near the surface of a waveguide and is relatively immune to bulk matrix effects. Planar waveguide TIRF has been used to measure a variety of analytes including hormones, toxins, bacteria, and viruses, leading to applications such as environmental and food safety monitoring, clinical diagnostics, and military defense. This technique has found numerous applications in the field of biosensors, in particular immunosensors and sensors for genetic analysis. The introduction of a fluorescent probe to a biomolecule has the advantage of allowing both site and spectral selection. Fluorescent labels have longer shelf lives, lower costs, and greater safety than radiolabels. An inherent advantage of using evanescent wave fluorescence is its surface-specific nature. While fluorescence-based detection provides sensitivity in terms of signal-to-background discrimination, the requirement for a fluorescent assay component may also be a disadvantage. The continued development and miniaturization of the biosensor instrumentation has led to systems that are fully automated, portable, and highly competitive with laboratory techniques. Such biosensors are now transitioning into the commercial market.

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Fluorescence based fiber optic and planar waveguide biosensors. A review
2016, Analytica Chimica Acta
Citation Excerpt :
The diameter of bulk waveguides, also known as “internal reflection elements” (IREs), is higher than the wavelength of the reflected light and sensing hot spots can be clearly distinguished, at the points of reflection, on the waveguide surface. Integrated optical waveguides (IOWs) are prepared by depositing a very thin layer, usually in the order of the light wavelength or less, of a high refractive index material (usually metal oxides such as SiO2, TiO2, Ta2O5, or Nb2O5) on a glass substrate [29–31]. The sensitivity of IOWs has shown to be much higher in fluorescence based studies than for IRE-based waveguides, however they are more difficult to prepare and light coupling into the optical waveguide is more difficult requiring the assistance of prism or grating arrangements [29,32,33].
The application of optical biosensors, specifically those that use optical fibers and planar waveguides, has escalated throughout the years in many fields, including environmental analysis, food safety and clinical diagnosis. Fluorescence is, without doubt, the most popular transducer signal used in these devices because of its higher selectivity and sensitivity, but most of all due to its wide versatility. This paper focuses on the working principles and configurations of fluorescence-based fiber optic and planar waveguide biosensors and will review biological recognition elements, sensing schemes, as well as some major and recent applications, published in the last ten years. The main goal is to provide the reader a general overview of a field that requires the joint collaboration of researchers of many different areas, including chemistry, physics, biology, engineering, and material science.
Automated portable array biosensor for multisample microcystin analysis in freshwater samples
2012, Biosensors and Bioelectronics
Citation Excerpt :
In addition, immunosensors based on different transduction schemes, such as optical (Herranz et al., 2010; Hu et al., 2009; Lindner et al., 2009; Long et al., 2009b), electrochemical (Loyprasert et al., 2008; Yu et al., 2009) and nuclear magnetic resonance (Ma et al., 2009) measurements have been also applied to MCs analysis but they usually have limited applicability for multisample analysis. Recent improvements in biosensor instrumentation have facilitated the commercialization of fully automated and portable devices, specially suited for field measurements, which can favorably compete with laboratory instrumental techniques (Sapsford et al., 2008). In the present study, a ready portable, low cost and easy-to-use array biosensor has been applied to MC monitoring in environmental waters.
An automated array biosensor based on evanescent-wave excitation has been developed for the detection of microcystins (MCs) in freshwater samples. The sensing surface consisted of microcystin-leucine-arginine (MCLR) covalently immobilized onto a planar waveguide (microscope slide). The binding of anti-MCLR monoclonal antibodies, spiked in the sample, to the immobilized MCLR was competitively inhibited by MCLR in solution and the amount of antibody bound to the patterned antigens was revealed using Cy5-labeled rabbit anti-mouse IgG. Surface chemistry has been optimized to improve biosensor performance in terms of sensitivity, regeneration ability and to avoid non specific binding for further application to environmental monitoring. The optimized biosensor assay presents an IC₅₀ value of 0.34 ± 0.01 μg/L, a detection limit of 16 ± 3 ng/L and a dynamic range from 0.06 to 1.5 μg/L MCLR, improving the performance of previously reported devices. Cross-reactivity to other related MCs, such as microcystin-RR (MCRR, 90%), microcystin-RR desmethylated (dm-MCRR, 95%) and microcystin-YR (MCYR, 91%), was also evaluated. The automated microarray can assay up to six different samples in parallel, with a total analysis time of about 60 min. The sensing surface was regenerated with 50 mM NaOH and each chip was reused for, at least, 15 assay-regeneration cycles without significant binding capacity loss. The immunosensor has been successfully applied to the direct analysis of MCs in surface water samples and the results were in close agreement with those provided by LC–MS/MS.
Optimization of antibody-conjugated magnetic nanoparticles for target preconcentration and immunoassays
2011, Analytical Biochemistry
Citation Excerpt :
Slides were either used immediately for patterning or stored in PBS at 4 °C until required. Patterning of the biotinylated Rb–anti-chick IgG (10 μg/ml) in PBS + 0.05% Tween (PBST) was carried out using a 6-channel patterning PDMS flow cell clamped onto the NeutrAvidin-functionalized slide surface and injecting the biotinylated capture antibody into 4 or 5 of the channels [6–8]. Biotinylated goat anti-mouse IgG (10 μg/ml in PBST) was introduced into the remaining channels for use as a negative control.
Biosensors based on antibody recognition have a wide range of monitoring applications that apply to clinical, environmental, homeland security, and food problems. In an effort to improve the limit of detection of the Naval Research Laboratory (NRL) Array Biosensor, magnetic nanoparticles (MNPs) were designed and tested using a fluorescence-based array biosensor. The MNPs were coated with the fluorescently labeled protein, AlexaFluor647–chicken IgG (Alexa647–chick IgG). Antibody-labeled MNPs (Alexa647–chick–MNPs) were used to preconcentrate the target via magnetic separation and as the tracer to demonstrate binding to slides modified with anti-chicken IgG as a capture agent. A full optimization study of the antibody-modified MNPs and their use in the biosensor was performed. This investigation looked at the Alexa647–chick–MNP composition, MNP surface modifications, target preconcentration conditions, and the effect that magnetic extraction has on the Alexa647–chick–MNP binding with the array surface. The results demonstrate the impact of magnetic extraction using the MNPs labeled with fluorescent proteins both for target preconcentration and for subsequent integration into immunoassays performed under flow conditions for enhanced signal generation.
Recent Advances in Optical Biosensors for Sensing Applications: a Review
2023, Plasmonics
Multi-labs-on-A chip based optical detection for atto-molar cancer markers concentration
2015, 2015 5th National Symposium on Information Technology: Towards New Smart World, NSITNSW 2015
Fluorescence and phosphorescence chemical sensors applied to water samples
2013, Smart Sensors, Measurement and Instrumentation

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Chapter 3 - PLANAR WAVEGUIDES FOR FLUORESCENCE BIOSENSORS

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