Rapid detection of carbapenemase-producing Enterobacteriaceae (CPE) represents a major challenge ... more Rapid detection of carbapenemase-producing Enterobacteriaceae (CPE) represents a major challenge for microbiology laboratories. We evaluated the BYG Carba v2.0 using a simplified protocol, which detects CPE in less than 30 minutes. This new procedure reduces the hands-on-time from 5 to one minute and only requires a limited amount of material (one to three colonies) thereby preventing the need for subculturing bacterial isolates to reach a larger amount of pure biomass. This multicentre study involved four European reference laboratories. For the 1181 isolates tested across four centres, BYG Carba v2.0 yielded overall sensitivity and specificity of 96.3% (CI95: 94.5–97.5) and 99.7% (CI95: 98.6–100) respectively. Considering only the 670 consecutive isolates tested prospectively, the BYG Carba v2.0 displayed overall positive and negative predictive values of 99.7% (CI95: 95.4–98.9) and 97.5% (CI95: 94.9–98.8). Regarding time to positivity, 85% of CPE detected were positive within ten...
A nanocomposite material, Ni 0.9 Zn 0.1 O/ZnO, was synthesized by controlled thermal treatment of... more A nanocomposite material, Ni 0.9 Zn 0.1 O/ZnO, was synthesized by controlled thermal treatment of the corresponding nickel zinc malonate previously prepared by coprecipitation in aqueous solution. The coexistence , structure and morphology of the Zn-doped nickel oxide, Ni 0.9 Zn 0.1 O and zinc oxide, ZnO, nanoparticles was confirmed by a set of instrumental techniques such as XRD, SEM and ToF-SIMS. The gas-sensing properties of the as-synthesized nanocomposites have been evaluated for CO, NO 2 , H 2 and the results show that the gas sensors based on the Ni 0.9 Zn 0.1 O/ZnO nanocomposites exhibit a good selectivity to NO 2 at low temperature (225 • C) and, comparing to ZnO and Ni 0.9 Zn 0.1 O individually, an increase in the response to CO gas at a high temperature (300 • C). The significant enhancement of the sensing performance of the Ni 0.9 Zn 0.1 O/ZnO nanocomposite is attributed to the formation of p-n junctions (metal oxide heterojunctions) between Ni 0.9 Zn 0.1 O (p-type semiconductor) and ZnO (n-type semiconductor) and to the catalytic activity of these metal oxides.
Accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) constitutes a major labora... more Accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) constitutes a major laboratory diagnostic challenge. We evaluated an electrochemical technique (the BYG Carba test) which allows detection of CPE in less than 35 min. The BYG Carba test was first validated in triplicate against 57 collection isolates with previously characterized β-lactam resistance mechanisms (OXA-48, n = 12; KPC, n = 8; NDM, n = 8; VIM, n = 8; IMP, n = 3; GIM, n = 1; GES-6, n = 1; no carbapenemase, n = 16) and against a panel of 10 isolates obtained from the United Kingdom National External Quality Assessment Service (NEQAS). The test was then evaluated prospectively against 324 isolates referred to the national reference center for suspicion of CPE. The BYG Carba test results were compared with those obtained with the Carba NP test using multiplex PCR sequencing as the gold standard. Of the 57 collection and the 10 NEQAS isolates, all but one GES-6-producing isolate were correctly identified b...
Screen-printed carbon electrodes were modified with polyaniline by electrochemical oxidation to p... more Screen-printed carbon electrodes were modified with polyaniline by electrochemical oxidation to produce a potentiometric pH transducer. The resulting pH sensor exhibited a fast, reproducible and sensitive potentiometric response of approximately 59 mV per pH unit from pH 4 to 8. The pH sensor response was found to be stable in time for up to one month. Such potentiometric response was obtained for thick polyaniline films. Thinner polymer films exhibited less sensitive responses and were found to have a smaller lifetime. The sensitivity of polyaniline to pH variations was then used to design an enzymatic biosensor. For that purpose, urease was immobilized on a polyelectrolyte multilayer film (PEM), obtained by the alternate deposition of charged polysaccharides (layer-by-layer assembly, LbL), over the polyaniline film. Covalent grafting of the urease enzyme to the PEM film was also tested using carbodiimide coupling reaction. The potentiometric response of this assembly to pH variations was similar to the one of polyaniline films, and its response to urea, from 10 −4 to 10 −1 mol L −1 , exhibited a very high sensitivity combined to fast response, good lifetime and reproducibility. The number of polyelectrolyte layers composing the PEM film was also found to affect the response of the urea sensors.
Original assemblies were prepared for use as sensitive films of potentiometric enzyme urea sensor... more Original assemblies were prepared for use as sensitive films of potentiometric enzyme urea sensors, and compared to identify the more efficient structure with respect to stability. These films included electrodeposited polyaniline, used as transducer, urease, used as catalyst, and biocompatible polyelectrolytes, used as a matrix to preserve the integrity of the enzyme in the sensitive film. Two kinds of assemblies were done: the first one consisted in the adsorption of urease onto a polyaniline film followed by the adsorption of a chitosan-carboxymethylpullulan multilayer film, while the second one consisted in the adsorption of a urease-chitosan multilayer film onto an electrodeposited polyaniline film. The morphological features and growth of these assemblies were characterized by scanning electron microscopy and quartz crystal microbalance, respectively. This allowed us to demonstrate that the assemblies are successfully formed onto the electrodes of the sensors. The potentiometric responses of both assemblies were then measured as a function of urea concentration using a home-made portable potentiostat. The electrochemical response of resulting sensors was fast and sensitive for both types of assemblies, but the stability in time was much better for the films obtained from alternative adsorption of urease and chitosan onto a layer of urease adsorbed over electrodeposited polyaniline.
... Several surface analysis techniques (ToF-SIMS, XPS, contact angle measurement, AFM, SEM, inte... more ... Several surface analysis techniques (ToF-SIMS, XPS, contact angle measurement, AFM, SEM, interferential polarized microscopy: Sarfus) are used to characterize surfaces that have been in contact with noninked PDMS rubber stamps. ... The ToF-SIMS intensities of Fig. ...
... SIMS Proceedings Papers. You have free access to this content Secondary ... Au and Pt deposit... more ... SIMS Proceedings Papers. You have free access to this content Secondary ... Au and Pt deposition were conducted at a rate of 0.1 nm/sec and 30 mA beam current for Au and 190 mA beam current for Pt. Measurement by ToF SIMS. ToF ...
This paper reports the development of a molecular fluorescence spectroscopy-based approach for th... more This paper reports the development of a molecular fluorescence spectroscopy-based approach for the determination of cadmium in seawater. Anthrylazamacrocycle derivatives-the fluorescence of which is enhanced when chelated to zinc or cadmium-are used as chemosensors. A detection limit of 5 nM has been found at pH 10 for both metals, and spectral shifts allow simultaneous Cd(II)/Zn(II) determination using multiwavelength analysis. While cadmium emission behavior is similar at pH 13, zinc is not detected anymore. This enables the selective detection of cadmium even at a high Zn(II)/Cd(II) ratio. The detection limit is 1 nM. Interferent removal and preconcentration have been developed using a Dowex resin, with a view to determine cadmium in seawater. A global procedure including interferent elimination, cadmium preconcentration (30 fold), and fluorescence detection at pH 13 has been evaluated on certified reference material SLEW-2.
Immobilized proteins or peptides are of critical importance for applications such as biosensing o... more Immobilized proteins or peptides are of critical importance for applications such as biosensing or cell culture. We analyze the structure of layers of a large variety of proteins and peptides, grafted on silicon substrates by different routes differing in the nature of the intermediate layer linking the biomolecules to the substrate, either a silane monolayer, or a polyelectrolyte multilayer made from synthetic or natural polymers. The structural analysis is essentially performed by X-ray reflectometry, which proves to be an efficient methodology not requiring the use of tagged biomolecules, capable of evaluating consistently the amount of grafted biomolecules per surface area with estimated precisions ranging from 10 to 20%. The study provides a quantitative basis for selecting one among a series of well-proofed and sturdy grafting methodologies and underlines the potential of XRR for assessing the amount of grafted biomacromolecules without requiring the expensive tagging of molecules. Our results also show that, for the coupling route resting on synthetic polyelectrolytes, the grafting density is significantly lower than for direct coupling over a silane layer. In contrast, when performed over a cushion based on polysaccharides, the grafting density is well above the values found for a dense layer grafted on a silane monolayer, indicating partial penetration and swelling of the polysaccharide cushion.
A process to fabricate stretchable and adherent gold tracks on flat silicone rubber substrates is... more A process to fabricate stretchable and adherent gold tracks on flat silicone rubber substrates is studied by X-ray photoelectron spectroscopy (XPS), static water contact angle measurement, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The process involves several steps: curing flat silicone substrate; removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5nm titanium and 80nm gold layers by e-beam evaporation; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. Its thickness is estimated to be around 20nm to 50nm. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure.
Two new donor-acceptor copolymers comprising a polythiophene backbone, and bearing phthalocyanine... more Two new donor-acceptor copolymers comprising a polythiophene backbone, and bearing phthalocyanine chromophores on the side chains have been prepared. Preliminary photophysical characterization of these materials by FTIR photoinduced absorption indicates that electron transfer from the polythiophene to the phthalocyanine units takes place.
Polyaniline is an electroactive polymer, which presents attractive properties for its use as a tr... more Polyaniline is an electroactive polymer, which presents attractive properties for its use as a transducer in electro-biosensors. Covalent binding of bioreceptors on the polymeric surface is necessary to perform selective and efficient bioanalyte detection. To achieve this goal, acrylic acid (AAc) is grafted on polyaniline films. Acrylic grafting on polyaniline introduces a new access to its biochemical functionalization. Carboxylic groups can be used for covalent immobilization of proteins, like ICHA antigen, by means of standard coupling agents (carbodiimide and succinimide). Surface analysis shows that there is a higher amount of antigen immobilized on the surface as compared with simple physical adsorption. The composition and structure of the modified surfaces are characterized by X-ray photoelectron spectroscopy (XPS) at each step of the process. Time-of-flight-secondary ion mass spectrometry (Tof-SIMS) is also used to analyze acrylic grafted polyaniline surfaces.
Rapid detection of carbapenemase-producing Enterobacteriaceae (CPE) represents a major challenge ... more Rapid detection of carbapenemase-producing Enterobacteriaceae (CPE) represents a major challenge for microbiology laboratories. We evaluated the BYG Carba v2.0 using a simplified protocol, which detects CPE in less than 30 minutes. This new procedure reduces the hands-on-time from 5 to one minute and only requires a limited amount of material (one to three colonies) thereby preventing the need for subculturing bacterial isolates to reach a larger amount of pure biomass. This multicentre study involved four European reference laboratories. For the 1181 isolates tested across four centres, BYG Carba v2.0 yielded overall sensitivity and specificity of 96.3% (CI95: 94.5–97.5) and 99.7% (CI95: 98.6–100) respectively. Considering only the 670 consecutive isolates tested prospectively, the BYG Carba v2.0 displayed overall positive and negative predictive values of 99.7% (CI95: 95.4–98.9) and 97.5% (CI95: 94.9–98.8). Regarding time to positivity, 85% of CPE detected were positive within ten...
A nanocomposite material, Ni 0.9 Zn 0.1 O/ZnO, was synthesized by controlled thermal treatment of... more A nanocomposite material, Ni 0.9 Zn 0.1 O/ZnO, was synthesized by controlled thermal treatment of the corresponding nickel zinc malonate previously prepared by coprecipitation in aqueous solution. The coexistence , structure and morphology of the Zn-doped nickel oxide, Ni 0.9 Zn 0.1 O and zinc oxide, ZnO, nanoparticles was confirmed by a set of instrumental techniques such as XRD, SEM and ToF-SIMS. The gas-sensing properties of the as-synthesized nanocomposites have been evaluated for CO, NO 2 , H 2 and the results show that the gas sensors based on the Ni 0.9 Zn 0.1 O/ZnO nanocomposites exhibit a good selectivity to NO 2 at low temperature (225 • C) and, comparing to ZnO and Ni 0.9 Zn 0.1 O individually, an increase in the response to CO gas at a high temperature (300 • C). The significant enhancement of the sensing performance of the Ni 0.9 Zn 0.1 O/ZnO nanocomposite is attributed to the formation of p-n junctions (metal oxide heterojunctions) between Ni 0.9 Zn 0.1 O (p-type semiconductor) and ZnO (n-type semiconductor) and to the catalytic activity of these metal oxides.
Accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) constitutes a major labora... more Accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) constitutes a major laboratory diagnostic challenge. We evaluated an electrochemical technique (the BYG Carba test) which allows detection of CPE in less than 35 min. The BYG Carba test was first validated in triplicate against 57 collection isolates with previously characterized β-lactam resistance mechanisms (OXA-48, n = 12; KPC, n = 8; NDM, n = 8; VIM, n = 8; IMP, n = 3; GIM, n = 1; GES-6, n = 1; no carbapenemase, n = 16) and against a panel of 10 isolates obtained from the United Kingdom National External Quality Assessment Service (NEQAS). The test was then evaluated prospectively against 324 isolates referred to the national reference center for suspicion of CPE. The BYG Carba test results were compared with those obtained with the Carba NP test using multiplex PCR sequencing as the gold standard. Of the 57 collection and the 10 NEQAS isolates, all but one GES-6-producing isolate were correctly identified b...
Screen-printed carbon electrodes were modified with polyaniline by electrochemical oxidation to p... more Screen-printed carbon electrodes were modified with polyaniline by electrochemical oxidation to produce a potentiometric pH transducer. The resulting pH sensor exhibited a fast, reproducible and sensitive potentiometric response of approximately 59 mV per pH unit from pH 4 to 8. The pH sensor response was found to be stable in time for up to one month. Such potentiometric response was obtained for thick polyaniline films. Thinner polymer films exhibited less sensitive responses and were found to have a smaller lifetime. The sensitivity of polyaniline to pH variations was then used to design an enzymatic biosensor. For that purpose, urease was immobilized on a polyelectrolyte multilayer film (PEM), obtained by the alternate deposition of charged polysaccharides (layer-by-layer assembly, LbL), over the polyaniline film. Covalent grafting of the urease enzyme to the PEM film was also tested using carbodiimide coupling reaction. The potentiometric response of this assembly to pH variations was similar to the one of polyaniline films, and its response to urea, from 10 −4 to 10 −1 mol L −1 , exhibited a very high sensitivity combined to fast response, good lifetime and reproducibility. The number of polyelectrolyte layers composing the PEM film was also found to affect the response of the urea sensors.
Original assemblies were prepared for use as sensitive films of potentiometric enzyme urea sensor... more Original assemblies were prepared for use as sensitive films of potentiometric enzyme urea sensors, and compared to identify the more efficient structure with respect to stability. These films included electrodeposited polyaniline, used as transducer, urease, used as catalyst, and biocompatible polyelectrolytes, used as a matrix to preserve the integrity of the enzyme in the sensitive film. Two kinds of assemblies were done: the first one consisted in the adsorption of urease onto a polyaniline film followed by the adsorption of a chitosan-carboxymethylpullulan multilayer film, while the second one consisted in the adsorption of a urease-chitosan multilayer film onto an electrodeposited polyaniline film. The morphological features and growth of these assemblies were characterized by scanning electron microscopy and quartz crystal microbalance, respectively. This allowed us to demonstrate that the assemblies are successfully formed onto the electrodes of the sensors. The potentiometric responses of both assemblies were then measured as a function of urea concentration using a home-made portable potentiostat. The electrochemical response of resulting sensors was fast and sensitive for both types of assemblies, but the stability in time was much better for the films obtained from alternative adsorption of urease and chitosan onto a layer of urease adsorbed over electrodeposited polyaniline.
... Several surface analysis techniques (ToF-SIMS, XPS, contact angle measurement, AFM, SEM, inte... more ... Several surface analysis techniques (ToF-SIMS, XPS, contact angle measurement, AFM, SEM, interferential polarized microscopy: Sarfus) are used to characterize surfaces that have been in contact with noninked PDMS rubber stamps. ... The ToF-SIMS intensities of Fig. ...
... SIMS Proceedings Papers. You have free access to this content Secondary ... Au and Pt deposit... more ... SIMS Proceedings Papers. You have free access to this content Secondary ... Au and Pt deposition were conducted at a rate of 0.1 nm/sec and 30 mA beam current for Au and 190 mA beam current for Pt. Measurement by ToF SIMS. ToF ...
This paper reports the development of a molecular fluorescence spectroscopy-based approach for th... more This paper reports the development of a molecular fluorescence spectroscopy-based approach for the determination of cadmium in seawater. Anthrylazamacrocycle derivatives-the fluorescence of which is enhanced when chelated to zinc or cadmium-are used as chemosensors. A detection limit of 5 nM has been found at pH 10 for both metals, and spectral shifts allow simultaneous Cd(II)/Zn(II) determination using multiwavelength analysis. While cadmium emission behavior is similar at pH 13, zinc is not detected anymore. This enables the selective detection of cadmium even at a high Zn(II)/Cd(II) ratio. The detection limit is 1 nM. Interferent removal and preconcentration have been developed using a Dowex resin, with a view to determine cadmium in seawater. A global procedure including interferent elimination, cadmium preconcentration (30 fold), and fluorescence detection at pH 13 has been evaluated on certified reference material SLEW-2.
Immobilized proteins or peptides are of critical importance for applications such as biosensing o... more Immobilized proteins or peptides are of critical importance for applications such as biosensing or cell culture. We analyze the structure of layers of a large variety of proteins and peptides, grafted on silicon substrates by different routes differing in the nature of the intermediate layer linking the biomolecules to the substrate, either a silane monolayer, or a polyelectrolyte multilayer made from synthetic or natural polymers. The structural analysis is essentially performed by X-ray reflectometry, which proves to be an efficient methodology not requiring the use of tagged biomolecules, capable of evaluating consistently the amount of grafted biomolecules per surface area with estimated precisions ranging from 10 to 20%. The study provides a quantitative basis for selecting one among a series of well-proofed and sturdy grafting methodologies and underlines the potential of XRR for assessing the amount of grafted biomacromolecules without requiring the expensive tagging of molecules. Our results also show that, for the coupling route resting on synthetic polyelectrolytes, the grafting density is significantly lower than for direct coupling over a silane layer. In contrast, when performed over a cushion based on polysaccharides, the grafting density is well above the values found for a dense layer grafted on a silane monolayer, indicating partial penetration and swelling of the polysaccharide cushion.
A process to fabricate stretchable and adherent gold tracks on flat silicone rubber substrates is... more A process to fabricate stretchable and adherent gold tracks on flat silicone rubber substrates is studied by X-ray photoelectron spectroscopy (XPS), static water contact angle measurement, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The process involves several steps: curing flat silicone substrate; removing uncured oligomers by hexane Soxhlet extraction; pre-stretching the substrate; activating the strained silicone surface by an oxygen plasma treatment; coating the strained substrate with 5nm titanium and 80nm gold layers by e-beam evaporation; and finally releasing the sample. The plasma treatment creates a thin brittle silica-like layer that temporarily increases the substrate's surface energy. Indeed the plasma treatment is followed by a hydrophobic recovery. As a consequence, the delay between plasma treatment and metal deposition has to be reduced as much as possible. The silica-like layer can be nicely observed after release. Its thickness is estimated to be around 20nm to 50nm. The entire process allows us to obtain stretchable metallized samples that remain conductive even after an excessive deformation leading to electrical failure.
Two new donor-acceptor copolymers comprising a polythiophene backbone, and bearing phthalocyanine... more Two new donor-acceptor copolymers comprising a polythiophene backbone, and bearing phthalocyanine chromophores on the side chains have been prepared. Preliminary photophysical characterization of these materials by FTIR photoinduced absorption indicates that electron transfer from the polythiophene to the phthalocyanine units takes place.
Polyaniline is an electroactive polymer, which presents attractive properties for its use as a tr... more Polyaniline is an electroactive polymer, which presents attractive properties for its use as a transducer in electro-biosensors. Covalent binding of bioreceptors on the polymeric surface is necessary to perform selective and efficient bioanalyte detection. To achieve this goal, acrylic acid (AAc) is grafted on polyaniline films. Acrylic grafting on polyaniline introduces a new access to its biochemical functionalization. Carboxylic groups can be used for covalent immobilization of proteins, like ICHA antigen, by means of standard coupling agents (carbodiimide and succinimide). Surface analysis shows that there is a higher amount of antigen immobilized on the surface as compared with simple physical adsorption. The composition and structure of the modified surfaces are characterized by X-ray photoelectron spectroscopy (XPS) at each step of the process. Time-of-flight-secondary ion mass spectrometry (Tof-SIMS) is also used to analyze acrylic grafted polyaniline surfaces.
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Papers by Sami Yunus