Nicole Jaffrezic-Renault

The effects of polarization of the incident light-modeling and analysis of a SPR multimode optical fiber sensor

A 3D skew ray modeling has been developed to consistently explain the experimental phenomena for an intrinsic SPR multimode optical fiber sensor. The effects of the polarization direction of the incident light at certain conditions have been clarified. This simulation is needed to accurately detect the variations of the refractive index of the bulk medium and of the thickness of the thin surface layer. More complete knowledge about light energy transmission by the skew ray in the multimode step-index fiber is obtained by this investigation.

Impedimetric immunosensor using avidin–biotin for antibody immobilization

The potentialities of an electrodeposited biotinylated polypyrrole film as an immobilisation matrix for the fabrication of impedimetric immunosensors are described. Biotinylated antibody (anti-human IgG), used as a model system, was attached to free biotin groups on the electrogenerated polypyrrole film using avidin as a coupling reagent. This immobilization method allows to obtain a highly reproducible and stable device. The resulting immunosensor has a linear dynamic range of 10-80 ng ml(-1) of antigen and a detection limit of 10 pg ml(-1). Furthermore, this immunosensor exhibited minor loss in response after two regeneration steps.

Sensitive detection of pesticides using a differential ISFET-based system with immobilized cholinesterases

Abstract Organophosporus pesticides were determined using a simple biosensor design. Enzymatic membranes prepared by cross-linking with BSA were deposited on a sensor chip consisting of two identical pH-FETs working in the differential mode (ENFET with enzyme, REFET without enzyme). Acetyl- and butyrylcholinesterase membranes were tested using acetyl- and butyrylcholine chloride as substrates. The decrease in the substrate steady-state response caused by exposure of the biosensor to pesticides [diisopropyl fluorophosphate (DFP), trichlorfon, paraoxon-methyl] was used to estimate the enzyme inhibition. The optimized parameters for the measurement procedure were determined and the detection limits were found to be 10 −12 M for DFP and 10 −6 M for paraoxon-methyl and trichlorfon.

Electrochemical impedance probing of DNA hybridisation on oligonucleotide-functionalised polypyrrole

We report a new approach for detecting DNA hybridisation using non faradaic electrochemical impedance spectroscopy. The technique was applied to a system of DNA probes bearing amine groups that are immobilized by covalent grafting on a supporting polypyrrole matrix functionalised with activated ester groups. The kinetics of the attachment of the ss-DNA probe was monitored using the temporal evolution of the open circuit potential (OCP). This measurement allows the determination of the time necessary for the chemical reaction of ss-DNA probe into the polypyrrole backbone. The hybridisation reactions with the DNA complementary target and non complementary target were investigated by non faradaic electrochemical impedance spectroscopy. Results show a significant modification in the Nyquist plot upon addition of the complementary target whereas, in presence of the non complementary target, the Nyquist plot is not modified. The spectra, in the form of Nyquist plot, were analysed with the Randles circuit. The transfer charge resistance R(2) shows a linear variation versus the complementary target concentration. Sensitivity and detection limit (0.2nM) were determined and detection limit was lower of one order of magnitude than that obtained with the same system and measuring variation of the oxidation current at constant potential.

A miniaturized urea sensor based on the integration of both ammonium based urea enzyme field effect transistor and a reference field effect transistor in a single chip

A urea biosensor prepared by covalent binding of urease directly to the surface of an ammonium-sensitive field effect transistor (FET) is described. Nonactin incorporated in carboxylated polyvinyl chloride was used to obtain the sensitive membrane of the ammonium-sensitive FET. The grafting of urease on the polyvinylchloride-COOH membrane surface was performed through carbodiimide coupling. The activity of the immobilized enzyme was spectrometrically controlled through the time-dependent disappearance of the absorbance of NADH at 340 nm. An apparent activity of 50% was found, compared with free enzyme. The sensitivity of the urea enzyme FET is 50 mV/pUrea working in a differential mode of 2 muM to 1 mM, this sensitivity being constant during 15 days. Finally, in order to test the potentialities of the urea biosensor for the environmental applications, the detection of heavy metal ions such as Cu(II) and Hg(II) in solution was performed by measuring the remaining activity of the inhibited enzyme.

Cell-based electrochemical biosensors for water quality assessment

During recent decades, extensive industrialisation and farming associated with improper waste management policies have led to the release of a wide range of toxic compounds into aquatic ecosystems, causing a rapid decrease of world freshwater resources and thus requiring urgent implementation of suitable legislation to define water remediation and protection strategies. In Europe, the Water Framework Directive aims to restore good qualitative and quantitative status to all water bodies by 2015. To achieve that, extensive monitoring programmes will be required, calling for rapid, reliable and cost-effective analytical methods for monitoring and toxicological impact assessment of water pollutants. In this context, whole cell biosensors appear as excellent alternatives to or techniques complementary to conventional chemical methods. Cells are easy to cultivate and manipulate, host many enzymes able to catalyse a wide range of biological reactions and can be coupled to various types of transducers. In addition, they are able to provide information about the bioavailability and the toxicity of the pollutants towards eukaryotic or prokaryotic cells. In this article, we present an overview of the use of whole cells, mainly bacteria, yeasts and algae, as sensing elements in electrochemical biosensors with respect to their practical applications in water quality monitoring, with particular emphasis on new trends and future perspectives. In contrast to optical detection, electrochemical transduction is not sensitive to light, can be used for analysis of turbid samples and does not require labelling. In some cases, it is also possible to achieve higher selectivities, even without cell modification, by operating at specific potentials where interferences are limited.

A novel urea sensitive biosensor with extended dynamic range based on recombinant urease and ISFETs.

A novel urea biosensor based on immobilised recombinant urease as sensitive element and ion sensitive field effect transistor as transducer was developed. Recombinant urease from E. coli with an increased Km was photoimmobilised in PVA/SbQ (poly(vinyl alcohol) containing styrylpyridinium) membrane and has demonstrated quite good performance as biosensitive element. Enzymatic field effect transistors based on such a bioselective element were studied in model buffer solutions. This biosensor demonstrated an extended dynamic range up to 80 mM, a quite good reproducibility (standard deviation of the sensor responses was approximately 2.5%, n= 20 for urea concentration 10 mM) and a high stability. Such characteristics fit with the analytical requirements needed for urea control in plasma and liquids used during renal dialysis.

Creatinine sensitive biosensor based on ISFETs and creatinine deiminase immobilised in BSA membrane.

A creatinine sensitive biosensor based on ion sensitive field-effect transistors (ISFETs) with immobilised creatinine deiminase (CD) is developed. CD is immobilised on the transducer surface by classical cross-linking with bovine serum albumin (BSA) in a glutaraldehyde (GA) vapour. The linear dynamic ranges of biosensors are between 0 and 5 mM creatinine concentration, and the sensor sensitivity depends on the sample buffer concentration. Minimal detection limit for creatinine determination in model solution with 144 mM NaCl and 5% BSA, pH 7.4, is about 10 muM. Biosensor responses are reproducible and stable during continuous work at least for 8 h, and the relative standard deviation of sensor response is approximately 3% (n=48, for creatinine concentrations of 0.2 and 0.6 mM). An investigation about storage stability of creatinine sensitive ENFETs kept in dry at 4-6 degrees C shows that biosensors demonstrate an excellent storage stability for at least 6 months and more. Moreover, creatinine sensitive enzymatic field-effect transistors (ENFETs), demonstrating very good performances, are very selective and specific and well suitable for hemodialysis monitoring.

New enzyme potentiometric sensor for hypochlorite species detection

Abstract Biochemical assay for hypochlorite couple (HOC1/OC1−) concentration in water solutions was developed. Acetylcholine sensitive enzyme sensor based on ion sensitive field effect transistors (ENFET) was prepared by cross-linking acetylcholinesterase (AChE) with bovine serum albumin in saturated glutaraldehyde vapour on the sensor chip and used for such purpose. The corresponding detection limit was at least about 10−5 M of HOC1/OC1− at pH 6.0-6.5. At these pH from 90% up to 100% of hypochlorite species were under the form of hypochlorous acid. Sensitivity of the developed biosensor to hypochlorite species depends on the concentration of acetylcholine and inhibition time. This phenomenon can be used to increase the sensitivity of such biosensor to hypochlorite species concentration and detection limit for inhibitor analysis can be decreased. The use of a pyridine-2-aldoxime methyliodide (PAM-2), a well known restoration activity agent for cholinesterases, did not give positive effect. So it can be concluded that the inhibition of AChE by HOCl/OCl− is due to another mechanism than those involved in the case of an inhibition by organophosphorous pesticides.

Surface Plasmon Resonance (SPR) Biosensors in Pharmaceutical Analysis

This review aims to highlight the applications of one of the most prominent optical biosensor technologies, surface plasmon resonance (SPR), in the drug discovery process and quality analysis of pharmaceutical compounds and their particularities. SPR assay formats and experimental issues are used for pharmacokinetic drug profiling, ADMET studies, high-throughput screening, and fragment-based drug screening, the last with an emphasis on the detection of small (drug) molecules. The classical method strengths and some applications of localized SPR and SPR imaging that are of high interest in the drug discovery process are presented, as well as possible challenges. While similar works treat separately the steps of drug discovery or focus only on the detection of drug residues in food or health safety, this review presents in a compact format the results and the progress obtained in both areas (drug discovery and quality analysis) based on the application of SPR biosensors.