Impedance Spectroscopy Technique for DNA Hybridization

The development of biosensors for detection and identification of DNA sequences by hybridization may reduce assay time and allow direct quantitation of the target. This article describes the use of impedance spectroscopy technique for digoxigeninthiol- labeled ssDNA probe immobilization, anti-digoxigenin binding and targeted DNA hybridization. The analysis of the impedance spectra in terms of equivalents circuits of the gold/electrolyte interface and gold/digoxigenin-thiol-labeled/electrolyte interface is discussed. The DNA hybridization shows a variation in the impedance spectra

Impedance spectroscopy technique for DNA hybridization

Abstract: The development of biosensors for detection and identification of DNA sequences by hybridization may reduce assay time and allow direct quantitation of the target. This article describes the use of impedance spectroscopy technique for digoxigeninthiol-labeled ssDNA probe immobilization, anti-digoxigenin binding and targeted DNA hybridization. The analysis of the impedance spectra in terms of equivalents circuits of the gold/electrolyte interface and gold/digoxigenin-thiol-labeled/electrolyte interface is discussed. The DNA hybridization shows a variation in the impedance spectra

Chemical detection in liquid media with a refractometric sensor based on a multimode optical fibre

In this paper the physical basis for the design of an optical fibre sensor suited for aqueous medium and gas phase based on the excitation of an evanescent wave at the core/cladding interface is developed. The detection based on the refractive index changes (between 1.41 and 1.45) of the infinite dielectric medium which can be an electrolyte or a sol-gel polymer deposited on the uncladed part of the fibre. Refractive indices of absorbent and volatile compounds such as fuel and unleaded gas were determined. Using a xerogel sensing layer as optical cladding, toluene detection in water was performed. The observed sensitivity is linear and the detection limit is 1% (in volume) toluene in water

Chemical detection in liquid media with a refractometric sensor based on a multimode optical fibre

In this paper the physical basis for the design of an optical fibre sensor suited for aqueous medium and gas phase based on the excitation of an evanescent wave at the core/cladding interface is developed. The detection based on the refractive index changes (between 1.41 and 1.45) of the infinite dielectric medium which can be an electrolyte or a sol-gel polymer deposited on the uncladed part of the fibre. Refractive indices of absorbent and volatile compounds such as fuel and unleaded gas were determined. Using a xerogel sensing layer as optical cladding, toluene detection in water was performed. The observed sensitivity is linear and the detection limit is 1% (in volume) toluene in water

An immunosensor for haemoglobin based on impedimetric properties of a new mixed self-assembled monolayer

International audienceA novel impedimetric immunosensor for the detection of haemoglobin has been developed by mixed self-assembled monolayers on An. First, a mixed self-assembled monolayer (SAMs) consisting of 1,2 dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (biotinyl-PE) and 16-mercaptobexadecanoic acid (MHDA) on gold electrodes was studied. The conformational properties of the SAMs were characterised by cyclic voltammetry and impedance spectroscopy. After blocking non-specific binding sites in the mixed monolayer using non-specific IgG, neutravidin was used to bind to biotinyl sites present in the mixed monolayer. Finally, biotinylated anti-haemoglobin IgG was immobilised to the tethered neutravidin. The membrane resistance R-m, obtained from the assembly, decreased gradually after the addition of non-specific IgG, neutravidin and anti-haemoglobin to the monolayer. This decrease could be attributed to a rearrangement in the structure of the SAMs. The detection of antibody-antigen reaction demonstrates that the potentiometric immunosensor exhibited high sensitivity and a detection limit of 20 ng/ml (approximately 0.3 nM). (c) 2005 Elsevier B.V. All rights reserved

A novel three-dimensional biosensor based on aluminum oxide: application for early-stage detection of human interleukin-10.

International audienceImmunosensors based on electrolyte-oxide-semiconductors (EOS) have been extensively researched over the last few decades. By electrochemical impedance spectroscopy (EIS) the specific molecular biorecognition of the antibody-antigen (Ab-Ag) can be detected providing an alternative quantitative system to immunoassay techniques. The electrochemical variations from a fabricated immunosensor can provide quantitative values for the analyte of interest at reduced costs and analysis time. In this context, a novel EOS substrate based on aluminum oxide (Al2O3) grown by atomic layer deposition on silicon was applied. The interaction between recombinant human (rh) interleukin-10 (IL-10) with the corresponding monoclonal antibody (mAb) for early cytokine detection of an anti-inflammatory response due to left ventricular assisted device implantation was studied. For this purpose, a 3D biosensor was composed of multi-walled carbon nanotubes with carboxylic acid functionalities (multi-walled carbon nanotubes-COOH) to increase the surface area for the range of human IL-10 detection. These were activated with N-hydroxysuccinimide and N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride for the immobilization of the anti-human IL-10 mAb. First, the interaction between the Ab and Ag was observed by fluorescence patterning to ensure that the biorecognition event was achievable. Then, EIS is explained for the quantification of commercial human IL-10 on this capacitance-based EOS macroimmuno-FET sensor

Temperature-Tuning of Optical Properties and Molecular Aggregation in AnE-PVstat Copolymer Solution

The correlation between the optical and morphological properties of an anthracene-containing poly­(phenylene ethynylene)-<i>alt</i>-(phenylenevinylene) statistical copolymer (AnE-PVstat) in solution has been investigated. As a function of temperature, the molecular aggregation in chloroform/chlorobenzene (CF:CB) solution was examined by means of absorbance and photoluminescence measurements. The study of the evolution of the 0–0 to the 0–1 photoluminescence (PL) ratio with temperature in the framework of the HJ-aggregate model unveiled the presence of both H- and J-like behaviors at room temperature. Upon increasing temperature, the interchain intermolecular coupling decreases, leading to a dissociation of H-aggregates. Hence, molecular torsions are facilitated, polymer planarity is reduced, and the intrachain electronic coupling decreases