Olivier Sire

Infrared glass fibers for in-situ sensing, chemical and biochemical reactions

Infrared optical fibres based on chalcogenide glasses have been designed for evanescent wave spectroscopy. The sensitivity of the optical sensor is improved in tapering the sensing zone by chemical etching and the working optical domain of the system has been tested on a chloroform sample. This original remote sensor, based on the analysis of infrared signatures, has been applied to follow the fermentation process in cider fabrication as well as to detect and monitor a bacterial biofilm.

Metabolic imaging of tissues by infrared fiber-optic spectroscopy: an efficient tool for medical diagnosis

Infrared fingerprints of molecules in biology contain much information on cells metabolism allowing one to distinguish between healthy and altered tissues. Here, to collect infrared signatures, we used evanescent wave spectroscopy based on an original infrared transmitting tapered glass fiber. A strict control of the fiber diameter in the tapered sensing zone allows high sensitivity and wide spectral range exploration from 800 to 3000 cm(-1). Then, merely in depositing the mouse liver biopsies on the fiber, this device has enable us to differentiate between tumorous and healthy tissues.

Chalcogenide glass fibers used as biosensors

The development of a new generation of chalcogenide infrared glass fibers allows making an IR sensor that permits recording the fingerprints of biomolecules in the mid infrared (MIR) range. The measurements are based on the general concept of evanescent wave spectroscopy. To improve the detection, the diameter of the fiber is locally reduced. To test this optical sensor, we measured metabolic anomalies in relation with hepatic pathologies. Mouse liver tissues have been used and MIR spectra have been recorded by a mere contact between tissues and the surface of the fiber. Spectral differences reflect metabolic alterations, these can be identified and assigned. Furthermore, histologic studies confirm these results.

Fiber evanescent wave spectroscopy using the mid-infrared provides useful fingerprints for metabolic profiling in humans

Fiber evanescent wave spectroscopy (FEWS) explores the mid-infrared domain, providing information on functional chemical groups represented in the sample. Our goal is to evaluate whether spectral fingerprints obtained by FEWS might orientate clinical diagnosis. Serum samples from normal volunteers and from four groups of patients with metabolic abnormalities are analyzed by FEWS. These groups consist of iron overloaded genetic hemochromatosis (GH), iron depleted GH, cirrhosis, and dysmetabolic hepatosiderosis (DYSH). A partial least squares (PLS) logistic method is used in a training group to create a classification algorithm, thereafter applied to a test group. Patients with cirrhosis or DYSH, two groups exhibiting important metabolic disturbances, are clearly discriminated from control groups with AUROC values of 0.94+/-0.05 and 0.90+/-0.06, and sensibility/specificity of 8684% and 8787%, respectively. When pooling all groups, the PLS method contributes to discriminate controls, cirrhotic, and dysmetabolic patients. Our data demonstrate that metabolic profiling using infrared FEWS is a possible way to investigate metabolic alterations in patients.

Mapping Bacterial Surface Population Physiology in Real-Time: Infrared Spectroscopy of Proteus Mirabilis Swarm Colonies

We mapped the space–time distribution of stationary and swarmer cells within a growing Proteus mirabilis colony by infrared (IR) microspectroscopy. Colony mapping was performed at different positions between the inoculum and the periphery with a discrete microscope-mounted IR sensor, while continuous monitoring at a fixed location over time used an optical fiber based IR–attenuated total reflection (ATR) sensor, or “optrode.” Phenotypes within a single P. mirabilis population relied on identification of functional determinants (producing unique spectral signals) that reflect differences in macromolecular composition associated with cell differentiation. Inner swarm colony domains are spectrally homogeneous, having patterns similar to those produced by the inoculum. Outer domains composed of active swarmer cells exhibit spectra distinguishable at multiple wavelengths dominated by polysaccharides. Our real-time observations agree with and extend earlier reports indicating that motile swarmer cells are restricted to a narrow (approximately 3 mm) annulus at the colony edge. This study thus validates the use of an IR optrode for real-time and noninvasive monitoring of biofilms and other bacterial surface populations.

Chalcogenide optical fibers for mid-infrared sensing

Abstract. Chalcogenide glasses are a matchless material as far as mid-infrared (IR) applications are concerned. They transmit light typically from 2 to 12 μm and even as far as 20 μm depending on their composition, and numerous glass compositions can be designed for optical fibers. One of the most promising applications of these fibers consists in implementing fiber evanescent wave spectroscopy, which enables detection of the mid-IR signature of most biomolecules. The principles of fiber evanescent wave spectroscopy are recalled together with the benefit of using selenide glass to carry out this spectroscopy. Then, two large-scale studies in recent years in medicine and food safety are exposed. To conclude, the future strategy is presented. It focuses on the development of rare earth-doped fibers used as mid-IR sources on one hand and tellurium-based glasses to shift the limit of detection toward longer wavelength on the other hand.

Control of vitellogenin genes expression by sequences derived from transposable elements in rainbow trout.

In most of oviparous animals, vitellogenins (VTG) are the major egg yolk precursors. They are produced in the liver under the control of estrogens. In rainbow trout (Oncorhynchus mykiss), the vtg genes cluster contains an unusually large number of almost identical gene copies. In order to identify the regulatory elements in their promoters, we used a combination of reporter plasmids containing genomic sequences including putative estrogen response elements (EREs) and we performed transient transfection assays in MCF-7 and yeast cells. We found a functional ERE corresponding to the sequence GGGGCAnnnTAACCT (rtvtgERE), which differs from the consensus ERE (ERE(cs)) by three base pairs. This non-palindromic ERE is located in the env gene of a retrotransposon relic, 180 base pairs upstream of the transcriptional start site. Fluorescence anisotropy experiments confirmed that the purified human estrogen receptor alpha (hERalpha) can specifically bind to rtvtgERE. Furthermore, we observe that the stability of hERalpha-ERE(cs) and hERalpha-rtvtgERE complexes is similar with equilibrium dissociation constants of 3.0nM and 6.2nM respectively, under our experimental conditions. Additionally, this rtvtgERE sequence displays a high E2-responsiveness through ER activation in cellulo. In the rainbow trout, the functional ERE (rtvtgERE) lies within promoter sequences which are mostly composed of sequences derived from transposable elements (TEs), which therefore may have acted as an evolutionary buffer to secure the proper expression of these genes.

Microplastics elutriation from sandy sediments: A granulometric approach

Although relatively easy to extract in the marine environment, microplastics are very difficult to recover when they are trapped in sediments. The elutriation column is one of the best tools currently available for extracting plastics from sediment, but with a high sand recovery yield. This study aims to address the following questions: (i) is it possible to use a sedimentological approach to limit the sand recovery? (ii) does the extraction velocity of the sand and plastic particles vary according to density and granulometry? (iii) what is the relative recovery efficiency obtained for dense polymer particles mixed with marine sand? Based on a new granulometric classification, different plastic particle-size fractions are defined. Their extraction velocities are experimentally determined on particles of sediment and different plastics (PA, PVC). The particle recovery experiments indicate that it is possible to extract >90% of dense plastic particles in cases of negligible sand recovery.

Chalcogenide glass fibers used for in situ infrared spectroscopy in biology and medicine

Chalcogenide glass optical fibers possess very low optical losses in the middle infrared range from 2 to 12 mm. They were used to implement remote infrared spectroscopy, known as Fiber Evanescent Wave Spectroscopy (FEWS). Due to their hydrophobic behavior, such sensor is especially suitable for application in biology and medicine where water is a nuisance to detect relevant information. Moreover, the design of the sensor using tapered fibers enables to improve the signal to noise ratio. Then, once coupled with unsupervised analysis technique such as Principle Component Analysis (PCA), it has been shown that this tool is efficient to differentiate between obese and control mice by recording their serum FEWS spectra. The same method has been carried out to detect in situ the both phenotypes of a bacterial culture.

Biological tissues infrared analysis by chalcogenide glass optical fiber spectroscopy

Owing to their low losses in the 2-12 micrometers region, the Te- As-Se glass fibers are used for infrared light transportation as well as sensing element based on evanescent wave absorption mechanism. The efficiency of the system is improved by tapering the fiber diameter in the sensing zone. With this kind of sensor, infrared spectra of biological tissue have been obtained. Spectra of mouse liver have been especially recorded in order to detect spectral differences between the healthy and the tumoral states of mouse liver.