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For the last few years, plasmon-based lasers have been investigated theoretically and experimentally. Several configurations have been reported. They are composed of quantum emitters coupled to a plasmonic structure. In this paper, we investigate the effect of the plasmon mode on the far-field and near-field characteristics of a nanolaser composed by a periodic array of metallic nanoparticles covered by gain materials under optical pumping. Two configurations were investigated. The first structure supported a localized surface plasmon (LSP) mode, while the second a surface lattice plasmon (SLP) mode. This theoretical work relies on semi-quantum calculations based on a four-level gain molecule and a time-domain approach. We demonstrated that lasing in a SLP mode requires a lower concentration of quantum emitters and generates a higher far-field emission with a lower threshold than lasing in a LSP mode. At nanoscale, near-field enhancement at the emission wavelength and above the threshold is 2 orders of magnitude higher with the SLP than the LSP mode. Our results with a general character show that designing a plasmon-based laser that sustains the SLP mode will result in a better lasing efficiency than with a LSP mode. (C) 2018 Optical Society of America

We demonstrated the use of a new organometallic nanoprobe for competitive surface-enhanced Raman scattering (SERS) immunoassay devoted to the detection of polycyclic aromatic hydrocarbons (PAH) such as benzo[a]pyrene (BaP) in seawater. The nanoprobes are gold nanoparticles (GNPs) labeled by a Raman reporter, the 5,5'-dithiobis(succinimidyl-2-nitrobenzoate) (DSNB) and functionalized with monoclonal antibodies anti-BaP. The antibodies are bound with a high specificity to the analyte while the GNPs enhanced the Raman scattering of the DSNB. This type of immunoassay involved the grafting of BaP onto a sensing surface. Thus, NH2-terminated self-assembled monolayer is formed on the surface of gold substrate using cysteamine. Amines finally reacted with 6-formylbenzo[a]pyrene. So, this SERS detection involves four steps: (i) the nanoprobes are incubated with the sample; (ii) a drop of the mixture is then put onto the substrate; (iii) the surface is rinsed; and (iv) the surface is analyzed by Raman spectroscopy. To synthesize the nanoprobes, firstly, we prepared GNPs according to Frens' method. Then, GNPs were spontaneously labeled by the DSNB Raman reporter, thanks to a strong gold-sulfur interaction. Thereafter, BaP antibodies were cross-linked to the DSNB labeled GNPs by reaction of proteins primary amino groups with N-hydroxyl succinimide (NHS). Before use in SERS detection, their activity was controlled by surface plasmon resonance technique. The present method allows us to detect BaP at trace concentration (2 nmol/L). The results demonstrate that the proposed method has a great potential for application in the monitoring of seawater.

Concerning in situ passive sampler deployment, several technical priorities must be considered. In particular, deployment time must be sufficiently long not only to allow a significant quantity to be accumulated to facilitate analysis but also to ensure that the signal is above the quantification limit and out of the blank influence. Moreover, regarding the diffusive gradient in thin films (DGT) technique, deployment time must also be sufficiently long (at least 5 days) to avoid the interactions of the solutes with the material diffusion layer of the DGT and for the steady state to be reached in the gel. However, biofouling occurs in situ and modifies the surface of the samplers. In this article, we propose a kinetic model which highlights the biofouling effect. This model was able to describe the mitigation of the flux towards the DGT resin observed on Cd, Co, Mn, Ni and Zn during a 22-day deployment in the Seine River. Over a period of 22 days, biofouling had a significant impact on the DGT concentrations measured, which were decreased twofold to threefold when compared to concentrations measured in unaffected DGTs.

Marine (= blue) biotechnology, i.e. the utilization of marine bio-resources as a target or source of biotechnological applications, is a field with massive potential for innovation and economic growth. In a context of rapid climate change and increasing pressure on natural resources, renewed interest in marine biotechnology has been promoted by application of recent methodological and technological advances, notably in bioprocessing and in the various –omics domains, to the study of marine biodiversity. Marine biological resources potentially represent a sustainable raw material for exploitation in diverse fields, including nutrition, health, agriculture, aquaculture, energy, environment, and cosmetics. Marine biotechnology is now recognized as a strategically important domain at European, national and regional levels. The present document, compiled by the Marine Biotechnology Working Group of the “Europole Mer”, aims to survey the skills, actors and principal infrastructures related to marine biotechnology in the Brittany and Pays de la Loire regions in the west of France in order to identify strengths and weaknesses and propose strategies to stimulate the future development of this strategic domain. Marine biotechnology is an integral part of the Smart Specialization Strategies of both of these maritime regions, which have more than 3000km of coast and numerous assets for becoming a hub of excellence for marine biotechnology. These include high quality, internationally renowned research laboratories and university courses in marine biology and engineering (bioprocessing), a strong inter-regional technology transfer ecosystem, and a dynamic and diversified network of mainly small-sized private-sector companies. However, marine biotechnology would benefit from greater inter-regional coherence and synergy between actors. This could be achieved by undertaking specific actions in the following domains: •• communication: implement a mutualized and offensive communicatio, Les biotechnologies marines (ou biotechnologies bleues), c’est à dire l’utilisation des bioressources marines en tant que cibles ou sources d’applications biotechnologiques, constituent un domaine qui recèle un énorme potentiel pour l’innovation et la croissance économique. Dans un contexte de changement climatique et de pression croissante sur les ressources naturelles, les biotechnologies marines connaissent actuellement un regain d’intérêt grâce d’une part aux progrès méthodologiques dans le domaine des bioprocédés et d’autre part à l’avancée majeure des connaissances sur la biodiversité marine accompagnée de la révolution dite « omique ». Les ressources biologiques marines constituent en effet une matière première durable pour une exploitation dans divers domaines d’application tels que la nutrition, la santé, l’agriculture, l’aquaculture, l’énergie, l’environnement et les produits cosmétiques. Les biotechnologies marines sont désormais reconnues comme un domaine d’importance stratégique aux niveaux européen, national et régional. Ce document, émanant du Groupe de travail sur les biotechnologies marines de l’Europôle Mer, vise à analyser les compétences, les acteurs et les principales infrastructures liées à la biotechnologie marine en Bretagne et dans les Pays de la Loire afin d’identifier les forces et les faiblesses du secteur et de proposer des stratégies pour stimuler le développement futur de ce domaine stratégique. Les biotechnologies marines figurent parmi les domaines d’innovation stratégiques de la Stratégie Régionale de Soutien à l’Innovation (SRI-SI) des deux Régions Bretagne et Pays de la Loire, qui cumulent plus de 3000 km de côtes et disposent de nombreux atouts pour constituer un pôle de compétences majeur en biotechnologies marines. Le Grand Ouest bénéficie en effet de laboratoires de recherche et de formations universitaires en biologie marine et en ingénierie de grande qualité et reconnus au niveau international, d’une dynamique très forte de

This paper presents a study on the calibration of conductivity sensors. The puropse is to demonstrate the effect of the salinity concentration on the response of conductivity sensor. Several experiments are performed on three sensors of different technologies: a Seabird Sbe37-SIP MicroCAT, a Falmouth Scientific Inc. IMCTD-MBP-D and a NKE Instrumentation Smatch. The analysis of the results shows an overall impact of the salinity level on the sensor response. This effect is discussed regarding the oceanographic requirements.

In this paper, a simple detection of a toxic algae, Alexandrium minutum, was developed using highly sensitive quartz crystal microbalance. In terms of performance, compared with other conventional analytical tools, the main interest of our immunosensor is based on a fast and direct detection of these living cells. This system requires the use of one monoclonal antibody directed against the surface antigen of A. minutum. We demonstrate that the whole living and motile algae are caught and detected. The high specificity of the biosensor is also demonstrated by testing several other dinoflagellate species. The frequency shift is correlated to the A. minutum cells concentration. This simple system is potentially promising for environmental monitoring purposes.

The primary objective of this study is the development of transparent thin film materials in the IR enabling strong infrared absorption of organic compounds in the vicinity of metal nanoparticles by the surface plasmon effect. For developing these optical micro-sensors, hetero-structures combining gold nanoparticles and chalcogenide planar waveguides are fabricated and adequately characterized. Single As2S3 and Ge25Sb10Se65 amorphous chalcogenide thin films are prepared by radio-frequency magnetron sputtering. For the fabrication of gold nanoparticles on a chalcogenide planar waveguide, direct current sputtering is employed. Fabricated single layers or hetero-structures are characterized using various techniques to investigate the influence of deposition parameters. The nanoparticles of gold are functionalized by a self-assembled monolayer of 4-nitrothiophenol. Finally, the surface enhanced infrared absorption spectra of 4-nitrothiophenol self-assembled on fabricated Au/Ge-Sb-Se thin films hetero-structures are measured and analyzed. This optical component presents a similar to 24 enhancement factor for the detection of NO2 symmetric stretching vibration band of 4-nitrothiophenol at 1336 cm(-1).

We demonstrate the possible use of organometallic nanoprobe on competitive surface-enhanced Raman scattering immunoassay for policyclic aromatic hydrocarbon detection in sea water. This type of SERS immunoassay is based on to capture Raman reporter-labeled immuno-Au onto the immobilized layer of antigens (benzo[a]pyrene) on the gold substrate after incubation of these nanoprobes with PAHs including in the sample. To realize nanoprobes, first we have prepared gold nanoparticles (GNPs) according to Frens’ method. Then, we have labeled GNPs by the Raman reporter of 5,5’-Dithiobis(succinimidyl-2-nitrobenzoate) (DSNB). Thereafter, Benzo[a]pyrene antibody was attached to the DSNB labeled GNPs. Before use in SERS detection, their activity was controlled by surface plasmon resonance. The present method allows us to detect benzo [a]pyren at traces concentration (ppb). The results demonstrate that the proposed method has the wide potential applications in the investigation of PAH pollutions of sea water (Figure).

The development of infrared sensing platform requires adapted materials. In this work, we used sputtered gold nanoparticles on a chalcogenide glass to demonstrate that these infrared materials can be used as substrate for surface enhanced infrared absorption (SEIRA) spectroscopy. The sputtering parameters were optimized to get the highest possible enhancement. To assess it, a self-assembled monolayer of 4-nitrothiophenol was used. These preliminary results are promising and pave the way for various configurations of waveguide for integrated optical components. (C) 2012 Elsevier B.V. All rights reserved.

Two quartz crystal microbalance oligonucleotide biosensors of a toxic microalga gene sequence (Alexandrium Minutum) have been designed. Grafting on a gold surface of 20-base thiol- or biotin-labeled probe, and selective hybridization with the complementary 20-base target, have been monitored in situ with a 27 MHz quartz crystal microbalance under controlled hydrodynamic conditions. The frequency of the set up is stable to within a few hertz, corresponding to the nanogram scale, for three hour experiments. DNA recognition by the two biosensors is efficient and selective. Hybridization kinetic curves indicate that the biosensor designed with the thiol-labeled probe is more sensitive, and that the biosensor designed with the biotin-labeled probe has a shorter time response and a higher hybridization efficiency.

The scientific question addressed in this work is: what hides beneath first order kinetic constant k (s(-1)) measured for hybridization of a DNA target on a biosensor surface. Kinetics hybridization curves were established with a 27 MHz quartz microbalance (9 MHz, third harmonic) biosensor, constituted of a 20-base probe monolayer deposited on a gold covered quartz surface. Kinetics analysis, by a known two-step adsorption-hybridization mechanism, is well appropriate to fit properly hybridization kinetics curves, for complementary 20-base to 40-base targets over two concentration decades. It was found that the K-1 (M-1) adsorption constant, relevant to the first step, concerns an equilibrium between non hybridized targets and hybridized pre-complex and increases with DNA target length. It was established that k(2) (s(-1)), relevant to irreversible formation of a stable duplex, varies in an opposite way to K-1 with DNA target length. (C) 2012 Published by Elsevier B.V.

A strategy to design DNA-biosensors by grafting probe-target duplex onto a 27 MHz quartz crystal microbalance gold surface is presented in this work. The idea that removing the DNA target after duplex grafting yields to a well accessible probe, and therefore to efficient target recognition, is investigated. Unfortunately, hybridization efficiency measured using such a straightaway protocol is equal to 15%, which is feeble by comparison with the 31% hybridization efficiency measured for biosensors designed with single-stranded probe. Successive DNA biosensors are designed in this work, taking into account phenomena that occur specifically in an interfacial environment, like non specific adsorption or exchange reactions between adsorbed molecules. A DNA-biosensor with an optimized biolayer in terms of probe accessibility and probe surface density is in fine designed: a 59% hybridization efficiency, for a complementary target including a 20-base non complementary sequence oriented toward the surface, is obtained for the biosensor designed with target-probe duplex. This hybridization efficiency is 3 times to 18% measured for biosensors designed with single-stranded probe. (C) 2012 Elsevier B.V. All rights reserved.

Cette étude s’inscrit dans le cadre du projet REI n°2010 34 0010 intitulé « Biofilms et corrosion d’alliages inoxydables en eau de mer », et a pour objectif de caractériser le biofilm responsable de l’activation de la corrosion des alliages inoxydables en eau de mer par une approche pluridisciplinaire, dans le but d’identifier les composantes responsables de ce type de corrosion. Ce biofilm spécifique est ainsi en cours de caractérisation par des méthodes de microscopie Apotome et de spectroscopie Raman. Ce poster a fait l'objet d'une présentation lors de l'Ecole thématique du CNRS : Voyage au centre d'un biofilm : physico-chimie des exopolymères de l'espace inter-cellulaire. Nancy, les 27 et 29 septembre 2011.

In the investigation of chemical pollutants, such as PAHs (Polycyclic Aromatic Hydrocarbons) at low concentration in aqueous medium, Surface-Enhanced Raman Scattering (SERS) stands for an alternative to the inherent low cross-section of normal Raman scattering. Indeed, SERS is a very sensitive spectroscopic technique due to the excitation of the surface plasmon modes of the nanostructured metallic film. The surface of quartz substrates was coated with a hydrophobic film obtained by silanization and subsequently reacted with polystyrene (PS) beads coated with gold nanoparticles. The hydrophobic surface of the SERS substrates pre-concentrates non-polar molecules such as naphthalene. Under laser excitation, the SERS-active substrates allow the detection and the identification of the target molecules localized close to the gold nanoparticles. The morphology of the SERS substrates based on polystyrene beads surrounded by gold nanoparticles was characterized by scanning electron microscopy (SEM). Furthermore, the Raman fingerprint of the polystyrene stands for an internal spectral reference. To this extent, an innovative method to detect and to quantify organic molecules, as naphthalene in the range of 1 to 20 ppm, in aqueous media was carried out. Such SERSactive substrates tend towards an application as quantitative SERS sensors for the environmental analysis of naphthalene.

This work deals with the design of a high sensitivity DNA sequence detector using a 50 MHz quartz crystal microbalance (QCM) electronic oscillator circuit. The oscillator circuitry is based on Miller topology, which is able to work in damping media. Calibration and experimental study of frequency noise are carried out, finding that the designed sensor has a resolution of 7.1 ng/cm(2) in dynamic conditions (with circulation of liquid). Then the oscillator is proved as DNA biosensor. Results show that the system is able to detect the presence of complementary target DNAs in a solution with high selectivity and sensitivity. DNA target concentrations higher of 50 ng/mL can be detected.

Lors d’une immersion en eau de mer, tous les matériaux et structures sont rapidement colonisés par des salissures d’origine biologique : des biofilms. La transformation des propriétés de surface dumatériau et la présence demicro- oumacro-organismes (bactéries, algues, balanes, larves) engendrent des risques accrus de corrosion localisée, la biodétérioration desmatériaux immergés, le blocage des fonctions mécaniques…Afin de contrôler le dépôt et le développement de ces biofilms, la méthode privilégiée est l’application de peintures anti-salissures. Cependant ces revêtements sont généralement toxiques pour l’environnement. C’est pourquoi, les travaux menés actuellement visent à isoler de nouvelles molécules, produites par les bactéries marines, dans le but de développer des moyens de luttes écologiques et non toxiques contre les biofilms indésirables.

Biofouling is ubiquitous in marine environment, and bacteria are among the first organisms to foul surfaces. They form biofilms which serve as focus for the attachment and growth of other organisms, such as invertebrates, sessile plants, and animals (Davis et al., 1989). Mature marine biofouling communities are complex, highly dynamic ecosystems (Fig.1) and once established are extremely difficult to eradicate (Holmstrom et al., 2002). For this reason the understanding of the mechanisms leading to marine bacterial attachment and its subsequent biofilm development are of great biological importance with obvious potential industrial outcomes. This development is conditioned by complex processes involving bacterial attachment to surfaces, growth, cell-to-cell communication, mobility and production of exoproducts constituting the biofilm matrix. Concerning attachment, the molecular strategies used by bacteria are diverse. They can employ pili, fimbria and a plethora of proteins regrouped under the term “adhesins” that recognize many different elements of the target (living or inert) surfaces (Pizarro-Cerda and Cossart, 2006; Fronzes et al., 2008). Although there is consistent data on human pathogenic bacteria attachment mechanisms, scarce information is available for marine bacteria. For this reason this project focused in the marine biofilm-forming bacterium Pseudoalteromonas sp. D41 (P. D41). This organism displays strong and competitive adhesion onto a wide variety of substrates, promoting subsequent biofilm development. Previous physicochemical studies in this strain related the high outer-shell protein content to its adhesion properties (Pradier et al., 2005; Leroy et al., 2008). For this reason, we attempted to unravel the molecular mechanisms responsible for these adhesive and competitive properties though a proteomic strategy, with particular attention to the outer membrane (OM) fraction.

Up to now, toxic species are monitored by expensive and time-consuming laboratory analysis of seawater samples: after a 24h decantation, the samples are observed with an optical microscope and the cell concentration per species is determined. In this context, systems able to detect HAB species directly underwater would be of great help. An assay based on an SPR biosensor was then developed for detecting Alexandrium minutum.

In the investigation of chemical pollutions, such as PAHs (Polycyclic Aromatic Hydrocarbons) at low concentration in aqueous medium, surface-enhanced Raman scattering (SERS) stands for an alternative to the inherent low cross-section of normal Raman scattering. Indeed, SERS is a very sensitive spectroscopic technique due to the excitation of the surface plasmon modes of the nanostructured metallic film.

It is shown that the surface-enhanced Raman scattering (SERS) technique can be applied to detect organic molecules during in situ experiments. To this purpose, we used trans-1,2-bis(4-pyridyl)ethylene (BPE) as a target molecule. Adsorbed on the SERS chemosensor surface and excited under laser, the vibration modes of the molecules can be identified. SERS chemosensors are based on quartz substrates functionalized by silanization and partially coated with gold nanoparticles. SERS measurements during shipboard experiments were made with a home-made in situ Raman spectrometer connected to a marinized micro-fluidic system. The device was designed to host chemosensors in order to ensure measurements with a flow cell. A theoretical limit of detection was estimated in the range of picomolar (pM) concentrations based on Freundlich isotherm calculations.

These days, many marine autonomous environment monitoring networks are set up in the world. These systems take advantage of existing superstructures such as offshore platforms, lightships, piers, breakwaters or are placed on specially designed buoys or underwater oceanographic structures. These systems commonly use various sensors to measure parameters such as dissolved oxygen, turbidity, conductivity, pH or fluorescence. Emphasis has to be put on the long term quality of measurements, yet sensors may face very short-term biofouling effects. Biofouling can disrupt the quality of the measurements, sometimes in less than a week. Many techniques to prevent biofouling on instrumentation are listed and studied by researchers and manufacturers. Very few of them are implemented on instruments and of those very few have been tested in situ on oceanographic sensors for deployment of at least one or two months. This paper presents a review of techniques used to protect against biofouling of in situ sensors and gives a short list and description of promising techniques.

Bacterial biofilms, frequently in association with algae, protozoa and fungi, are found on all submerged structures in the marine environment. Biofilms are responsible for a range of surface‐associated and diffusible signals, which may moderate the settling behaviour of cells, spores and larvae. Thus, marine microorganisms are a new source of bioactive compounds, which enhance or inhibit the settlement of organisms.

Marine organisms represent a rather unexplored source of new activity and biological functions of molecules for biotechnologies. The research in chemical ecology of the marine environment leads to looking at metabolites of recognition or defence produced by these models. Marine bacteria belonging to the Pseudoalteromonas genus of the Gammaproteobacteria class are often found in association with marine eukaryotes, and their ability to produce a variety of biological activities attracted a particular attention. The marine Pseudoalteromonas sp. 3J6 and D41 were selected for their capacity to inhibit the biofilm formation of other bacteria. The study of antibiofilm metabolites synthesised by marine bacteria 3J6 and D41 biofilms can lead to the development of new anti-fouling compounds or applications in surface hygiene. The main originality of these compounds is to be specifically antibiofilm, they have no activity against planctonic bacteria.

Since 1998, the European Biocidal Products Directive (BPD; 98/8/EC), applied to 23 product types (PT) for specific uses, including PT 21 the « antifouling products », regulates biocidal products before they are placed on the market. On the one hand, the efficacy of active substances and their formulations must be demonstrated for their specific employment ; on the other hand their non impact on workers neither users and environment must be proved and specifically against non target species. Standard protocols for the assessment of efficacy or ecotoxicity of antifouling substances are proposed within the framework of the Ecopaint and Paintclean projects which are founded by the french industry Ministery and labellised by the “Pôle Mer” (Paca and Brittany). The potential toxicity of actives substances as well as paints or their elutriates is assessed in vitro on six trophic levels following marine TGD recommendations (2003): bacteria, phytoplancton, crustacea, mollusc, echinoderm and fish. The potential impact of antifouling paints on the modification of the condition index of oysters (10 to 12 months exposure) is observed in situ. The efficacy of active substances and paints is also tested both in vitro and in situ In in vitro testing, the adhesion of marine pioneer bacteria is followed in presence of not of the active substances . While the biofouling development is observed on painted surfaces exposed on rafts as well as on vessel hulls during 12 months. In situ exposure could be performed in specific and/or different environments and on different kind of vessels (geographic zone, speed, duration of exposure…).

For the last few years there is a more and more pressing need to develop system for detecting HAB at their early stage. Researchers have then been working on new in situ sensor. In this paper a submarine transducer based on surface plasmon resonance is reported. It demonstrated a refractive index resolution of 3.10(-6), which is promising for later phytoplankton detection.

This work deals with the development of a high sensibility DNA biosensor based on a 50MHz Quartz Crystal Microbalance (QCM) Oscillator Electronic Circuit. The designed QCM oscillator sensor is able to detect the presence of complementary DNAs in a solution that match the sequence on a given strand in function of the changes in the output frequency of the oscillator. The design is adapted so that the Barkhausen condition is satisfied even when the quartz is immerged in liquid media. Also a comparative study of the developed 50MHz biosensor in front of a QCM oscillator with smaller frequency is carried out, with object of checking if the sensibility of the oscillator increases, allowing to detect smaller concentrations of the complementary DNA.

This paper reports the development of a sensor based on surface-enhanced Raman scattering (SERS) for analyses in sea-water. Polycyclic aromatic hydrocarbons (PAHs) are targeted by these sensors and their detection in situ summons up chemical synthesis and optical development. Firstly, a relevant synthesis of SERS active substrates based on gold nanostructures is presented. Different kinds of substrates have been synthesized under variable experimental conditions to modify some parameters such as i) gold shape, size and distribution and such as ii) chemical functionalization: (i) gold nanoparticles were prepared either by chemical reduction of HAuCl4 or by physical deposition. (ii) Substrates were functionalized by hydrophobic films to allow nonpolar molecules pre-concentration. Low concentration from ppb to ppm of PAHs were detected with a Raman microscope designed for lab experiments. Sensors exhibit strong enhancement of Raman scattering from molecules adsorbed on the films. Spectra were recorded for two PAHs (naphthalene and pyrene) in artificial sea-water with limits of detection of 10ppb for both with a short integration time (10s) and a low incident laser power (~0.1mW). Active substrate surface morphology was characterized with scanning electron microscopy (SEM) measurements. Secondly, an home-made in situ Raman spectrometer was developed and has been connected to a micro-fluidic system. This system was designed to host SERS-active sensors in order to ensure measurements with a flow cell. This original configuration of in situ Raman spectroscopy was then achieved. Such a device is now ready to use to confirm the PAH detection at ppb levels during the offshore experiments thanks to SERS sensors.

Among marine algae species, Alexandrium minutum produces a phycotoxin called paralytic shellfish poisoning (PSP) that is introduced in the food chain through the ingestion of phytoplankton by shellfishs, and later by human consumers. Thus, in situ monitoring of A. minutum proliferation in coastal seawater is of great economical importance for marine resources exploitation. Here, we propose a rapid test for the detection of A. minutum by surface plasmon resonance spectroscopy. First, whole genomic DNA is extracted from the algae. Second, a 677 bp long portion of the 28S ribosomal DNA is amplified by PCR. Third, the PCR product is detected by surface plasmon resonance spectroscopy onto a DNA functionalized gold substrate.

Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the mid-infrared spectral range we have developed a biosensor that can collect information on whole metabolism alterations, rapidly and in situ. Thanks to this sensor it is possible to collect infrared spectra by remote spectroscopy, by simple contact with the sample. In this way, we tried to determine spectral modifications due, on the one hand, to cerebral metabolism alterations caused by a transient focal ischemia in the rat brain and, in the other hand, starvation in the mouse liver. We also applied a microdialysis method, a well known technique for in vivo brain metabolism studies, as reference. In the field of integrated microsensors, reactive ion etching was used to pattern rib waveguides between 2 and 300 mu m wide. This technique was used to fabricate Y optical junctions for optical interconnections on chalcogenide amorphous films, which can potentially increase the sensitivity and stability of an optical micro-sensor. The first tests were also carried out to functionalise the Chg planar waveguides with the aim of using them as (bio) sensors.

Harmful algal blooms represent a major threat to marine production, and particularly to shellfish farming. Alexandrium minutum, which causes paralytic shellfish poisoning, is occurring with increasing frequency along European coasts. Current regulatory methods to analyze environmental samples are tedious and time consuming because they require taxonomists and involve animal experiments. New rapid detection methods, such as immunoassays, are needed to ensure a fast alert system and for field studies of algal ecodynamics. Rat monoclonal antibodies were raised and selected for their ability to specifically recognize a surface antigen for the A. minutum strain AM89BM from the Bay of Morlaix, France. A whole-cell ELISA was designed, leading to the selection of one AMI6 mAb that was selected for its performance in a large set of immunochemical formats. Moreover, AMI6 mAb displayed no detectable cross-reactivity with most algae found in similar biotopes, particularly those which might be mistaken during a conventional light microscope counting Heterocapsa triquetra, Scrippsiella trochoidea, Karenia mikimotoi, and two strains of Alexandrium tamarense, either toxic or not. Using colloidal gold conjugates on immunodecorated cells, we used electron microscopy to show that AMI6 mAb targets an exposed antigen at the surface of A. minutum. It was noted that this antibody could work with many preparations of A. minutum cells, i.e. fresh, frozen or dried cells. The detection limit in the whole-cell ELISA was found to be 10 cells per well. This assay displayed sensitivity and specificity when used for the analysis of natural seawater samples. A large set of immunochemical formats, using either AMI6 mAb or related antibodies from this series, could be further envisaged for designing environmental biosensors.

In this work QCM technologies were used to set up a DNA based biosensor dedicated to the detection of toxic micro-algae in the environment. Up to now, appropriate detection were not achieved for different reasons as the possibility of regeneration, the capability of multidetection or the detection of very low DNA target concentration. For these reasons different configurations were examined based on in-situ and fast regeneration, supramolecular chemistry of DNA and high sensitive gravimetric devices. In a first step an OligoDesoxyRibonucleotide 5’ tailed with a disulfide group (SH-ODN) designed to be a specific molecular probe for the toxic micro-algae Alexandrium minutum was grafted on the quartz surface resonators. Kinetics of probe immobilization and of hybridization reactions with different targets were followed by monitoring the microbalance frequency changes of QCM working at 27 MHz and 50 MHz. These first experiments also showed that regeneration of this disulfide DNA QCM biosensor was possible as the target could be removed by alkaline dehybridization. Finally, to design a reversible QCM-DNA-biosensor in order to detect successively different targets, a modification of the grafted probe was attempted based on a complex structure of DNA assemblies.