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Couture M.,University of Montreal | Live L.S.,University of Montreal | Dhawan A.,Indian Institute of Technology Delhi | Masson J.-F.,University of Montreal | Masson J.-F.,Center for Self Assembled Chemical Structures

The debate is still ongoing on the optimal mode of interrogation for surface plasmon resonance (SPR) sensors. Comparative studies previously demonstrated that nanoparticles exhibiting a localized SPR (LSPR) have superior sensitivity to molecular adsorption processes while thin Au film-based propagating SPR is more sensitive to bulk refractive index. In this paper, it is demonstrated that nanohole arrays (1000 nm periodicity, 600 nm diameter and 125 nm depth), which support both LSPR and propagating SPR modes, exhibited superior sensitivity to bulk refractive index and improved detection limits for IgG sensing by using the Kretschmann configuration. The greater sensitivity to IgG detection in the Kretschmann configuration was obtained despite the shorter penetration depth of nanohole arrays excited in the enhanced optical transmission (EOT) configuration. The decay length of the electromagnetic field in EOT mode was estimated to be approximately 140 nm using a layer-by-layer deposition technique of polyelectrolytes (PAH and PSS) and was confirmed with 3D FDTD simulations, which was lengthen by almost a factor of two in the Kretschmann configuration. Spectroscopic data and field depth were correlated with RCWA and FDTD simulations, which were in good agreement with the experimental results. Considering these analytical parameters, it is advantageous to develop sensors based on nanohole arrays in the Kretschmann configuration of SPR. © 2012 The Royal Society of Chemistry. Source

Breault-Turcot J.,University of Montreal | Masson J.-F.,University of Montreal | Masson J.-F.,Center for Self Assembled Chemical Structures
Chemical Science

Chemical measurements are rarely performed in crude blood due to the poor performance of sensors and devices exposed to biofluids. In particular, biosensors have been severely limited for detection in whole blood due to surface fouling from proteins, the interaction of cells with the sensor surface and potential optical interference when considering optical methods of analysis. To solve this problem, a dialysis chamber was introduced to a surface plasmon resonance (SPR) biosensor to create a diffusion gate for large molecules. This dialysis chamber relies on the faster migration of small molecules through a microporous membrane towards a sensor, located at a specified distance from the membrane. Size filtering and diffusion through a microporous membrane restricted the access of blood cells and larger biomolecules to a sensing chamber, while smaller, faster diffusing biomolecules migrated preferentially to the sensor with limited interference from blood and serum. The affinity of a small peptide (DBG178) with anti-atherosclerotic activity and targeting type B scavenger receptor CD36 was successfully monitored at micromolar concentrations in human serum and blood without any pre-treatment of the sample. This concept could be generally applied to a variety of targets for biomolecular interaction monitoring and quantification directly in whole blood, and could find potential applications in biochemical assays, pharmacokinetic drug studies, disease treatment monitoring, implantable plasmonic sensors, and point-of-care diagnostics. This journal is © The Royal Society of Chemistry 2015. Source

Zhao S.S.,University of Montreal | Bichelberger M.A.,University of Montreal | Colin D.Y.,University of Montreal | Pelletier J.N.,University of Montreal | And 2 more authors.

A competitive binding assay based on localized surface plasmon resonance (LSPR) of folic acid-functionalized gold nanoparticles (FA-AuNPs) and human dihydrofolate reductase enzyme (hDHFR) was developed to detect nanomolar to micromolar concentrations of the widely applied anti-cancer drug, methotrexate (MTX). By the nature of the competitive assay for MTX, the LSPR shift from specific binding between FA-AuNPs and the free enzyme was inversely proportional to the concentration of MTX. In addition, the dynamic range for MTX was tuned from 10-11 to 10-6 M by varying the concentration of hDHFR from 1 to 100 nM. Inter-day reproducibility and recovery of MTX spiked in phosphate buffer saline (PBS) were excellent. Potential interferents such as FA, trimethoprim (TMP) and 4-amino-4-deoxy-N-methylpteroic acid (DAMPA) did not occur in the concentration range of interest for MTX. Clinical samples of human serum from patients undergoing MTX chemotherapy were analyzed following a simple solid-phase extraction step to isolate MTX from the serum matrix, with a limit of detection of 155 nM. Validation of the LSPR method was carried out in comparison to Fluorescence Polarization Immunoassay (FPIA), a commonly used method in clinical settings, and LC-MS/MS, a reference technique. The results of the LSPR competitive assay compared well to FPIA and LC-MS/MS, with a slope of 2.4 and 1.1, respectively, for the correlation plots. The method established herein is intended for therapeutic drug monitoring (TDM) of MTX levels in patients undergoing chemotherapy to ensure safety and efficacy of the treatment. © 2012 The Royal Society of Chemistry. Source

Couture M.,University of Montreal | Liang Y.,Dalian University of Technology | Poirier Richard H.-P.,University of Montreal | Faid R.,University of Montreal | And 3 more authors.

Modern photonics is being revolutionized through the use of nanostructured plasmonic materials, which confine light to sub-diffraction limit resolution providing universal, sensitive, and simple transducers for molecular sensors. Understanding the mechanisms by which light interacts with plasmonic crystals is essential for developing application-focussed devices. The strong influence of grating coupling on electromagnetic field distribution, frequency and degeneracy of plasmon bands has now been characterized using hexagonal nanohole arrays. An equation for nanohole arrays was derived to demonstrate the strong influence of incidence and rotation angle on optical properties of 2D plasmonic crystals such as nanohole arrays. Consequently, we report experimental data that are in strong agreement with finite difference time-domain (FDTD) simulations that clearly demonstrate the influence of the grating coupling conditions on the optical properties (such as plasmon degeneracy and bandwidth), and on the distribution of the plasmon field around nanohole arrays (including tuneable penetration depths and highly localized fields). The tuneable 3D plasmon field allowed for controlled sensing properties and by increasing the angle of incidence to 30 degrees, the resonance wavelength was tuned from 1000 to 600 nm, and the sensitivity was enhanced by nearly 300% for a protein assay using surface plasmon resonance (SPR) and by 40% with surface-enhanced Raman scattering (SERS) sensors. © 2013 The Royal Society of Chemistry. Source

Murray-Methot M.-P.,University of Montreal | Ratel M.,University of Montreal | Masson J.-F.,University of Montreal | Masson J.-F.,Center for Self Assembled Chemical Structures | Masson J.-F.,Biosensors
Journal of Physical Chemistry C

A systematic study of the optical properties and analytical response is reported for gold and silver nanohole arrays with different hole diameters with a fixed periodicity of 450 nm. Nanosphere lithography in combination with oxygen plasma etching has been used to fabricate the nanohole arrays. The plasmonic response of nanohole arrays is characterized in transmission spectroscopy (λ = 500-1000 nm spectral region), which varied with the metal composition and diameter of the nanoholes. The sensitivity to bulk refractive index (in nm/RIU) and the full width at half-maximum (FWHM) were measured for each plasmonic mode to compare the biosensing potential of the various nanohole arrays. A sensitivity of nearly 400 nm/RIU was observed and was maximal with the plasmonic band at λ = 554 nm for Ag nanohole arrays with the smallest hole diameter of 120 nm. Generally, the ratio of the full height (transmission intensity) and FWHM is constant for various hole diameters with Au nanohole arrays, whereas it improves for Ag nanohole arrays with smaller hole diameters. Various bimetallic nanohole arrays composed of a Ag underlayer covered with Au were fabricated with a hole diameter of 254 ± 20 nm and a depth of 50 ± 12 nm. Sensitivity and FH/FWHM ratio are improved for Au on Ag nanohole arrays compared with nanohole arrays of pure metal. © 2010 American Chemical Society. Source

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