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International audience; Developing electrolyzers operating under neutral or near-neutral conditions with catalysts based only on earth-abundant metals is highly desirable with a view to reduce the cost of hydrogen production from water splitting reaction and avoid the environmental issues related to corrosion usually encountered with alkaline electrolyzers. Herein, we report a highly active and stable anode material for oxygen evolving reaction (OER) in mild-pH conditions based on cobalt oxide-nanoparticles embedded into a poly(pyrrole-alkylammonium) matrix (denoted PPN+-CoOx). Examples of hybrid materials combining metal oxide nanoparticles as OER catalysts within a polymer film are still rare. However, they are very promising to control the formation and the size of metal particles in view to enhance the electrochemically active surface area and thus the electrocatalytic performances. Our strategy consists in electroprecipitating Co0 nanoparticles by reduction of an anionic cobalt oxalate complex into the cationic PPN+ film, the latter being previously deposited onto an electrode surface by electropolymerization. The Co0 nanoparticles within the composite are then partially in-situ oxidized under air exposure into CoO, and then finally fully oxidized into CoOx by successive scans between 0 and 1.2 V vs Ag/AgCl in a borate buffer at pH 9.2. This nanocomposite material is highly structured with around 30 nm-large CoOx nanoparticles well dispersed into the polypyrrole film conferring a high OER electrocatalytic activity at near neutral pH of 9.2 with exceptional values of mass activity and turnover frequency of 3.01 A mg-1 and 0.46 s-1 respectively, at an overpotential of 0.61 V and with a cobalt loading of 1.34 µg cm-2. These performances place the PPN+-CoOx electrode among the most active anodes described in the literature employing cobalt oxide under mild pH conditions. In addition, when the PPN+-CoOx material is electrodeposited on carbon paper with a higher roughness than a simple carbon electrode, the physisorption of the film on the electrode is considerably enhanced resulting in a stable catalytic current over more than 43 h. Post electrolysis characterizations by SEM and EDX confirm the integrity of the PPN+-CoOx material after long hours of electrocatalysis. This demonstrates the beneficial role of the polypyrrole matrix in the achievement of very stable and highly active anodes for water oxidation.

A biosensor based on the release of the enzyme substrate from its structure was developed for the inhibitive detection of benzoic acid. A polyurethane support comprising two perforated microcapsules (800 μm in diameter) filled with methylene blue as a model compound and covered with a conductive deposit of multiwalled carbon nanotubes, continuously released this stored dye for 24 h. An increase in methylene blue concentration of 0.5–0.75 μmol L-1 h-1 and 1.5–2 μmol L-1 h-1, in the presence and absence of the multiwalled carbon nanotube coating, respectively, was demonstrated by UV–vis spectroscopy in a 2 mL UV cuvette. The same configuration with microcapsules filled with catechol was modified by a laponite clay coating containing tyrosinase enzyme. The resulting biosensor exhibits a constant cathodic current at −0.155 V vs AgCl/Ag, due to the reduction of the ortho-quinone produced enzymatically from the released catechol. The detection of benzoic acid was recorded from the decrease in cathodic current due to its inhibiting action on the tyrosinase activity. Reagentless biosensors based on different deposited quantity of tyrosinase (100, 200, 400 and 600 μg) were investigated for the detection of catechol and applied to the detection of benzoic acid as inhibitor. The best performance was obtained with the 400 μg-based configuration, namely a detection limit of 0.4 μmol L-1 and a sensitivity of 228 mA L mol−1. After the inhibition process, the biosensors recover 97–100% of their activity towards catechol, confirming a reversible inhibition by benzoic acid.

For four decades, the functionalization of electrodes by biomaterials based on electrogenerated polymers, carbon nanotubes and / or nano-objects, was widely used in the field of analytical chemistry and energy conversion. Recently, we redesigned enzymatic bioelectrodes in order to produce original objects. An innovative concept of reagentless biosensors based on enzymatic reduction of oxygen was developed by trapping and releasing the substrate of the enzyme (catechol) from the structure of the biosensor. A polyurethane support modified by two perforated microcapsules filled with catechol was easily transformed into a bioelectrode by the successive deposition of multiwalled carbon nanotubes and a mixture of laponite clay and tyrosinase enzyme [1]. On the other hand, the development of glyconanoparticles resulting from the self-assembly of block copolymers composed of polystyrene and cyclodextrin as an inclusion site will be reported. These glyconanoparticles, which are stable in suspension in aqueous media, have an outer layer composed of cyclodextrin [2]. The latter allows a post-functionalization of the nanoparticle by hydrophobic molecules through host-guest interactions. It appears that it is possible to modulate the site density of βCD at the surface of the shell of the hybrid glyconanoparticles while maintaining its inclusion properties. Moreover, the anchoring of glyconanoparticles to the surface of electrodes has been carried out by host-guest interactions with electrogenerated polymers. The efficient immobilization of the nanoparticles allows the anchoring of multilayers of biotinylated glucose oxidase. Finally, a new generation of bioelectrodes for oxygen reduction and electrical energy production will be described. This approach is based on the design of flat electrodes made of permeable and conductive materials defining a very thin microcavity with a large surface area containing, in a microvolume, enzymes in powder form. The concept has been demonstrated with bilirubin oxidase (BOD) for the electroenzymatic reduction of oxygen in water. Besides the influence of the amount of enzyme trapped in the microcavity on the performance of the bioelectrode, the functionalization of the electrodes by adsorption of redox mediators or compounds allowing an orientation of the BOD favorable to electron transfer was also explored. After 5 months of storage in an aqueous buffer, the bioelectrode exhibits 20% of its initial electro-enzymatic activity. Y. Nedellec, C. Gondran, K. Gorgy, S. MC Murtry, O. El Mazria, P. Agostini, S. Cosnier. Biosens. Bioelectron., 180, 113137-113141(2021). M. Carrière, P. H. M. Buzzetti, K. Gorgy, M. Mumtaz, C. Travelet, R. Borsali, S. Cosnier. Nanomaterials 11 (2021) 1162. doi.org/10.3390/nano11051162.

WS2 nanotubes functionalized with carboxylic acid functions (WS2-COOH) were used for improved immobilization of the enzyme tyrosinase in order to form an electrochemical biosensor towards catechol and dopamine. The nanotubes were deposited on glassy carbon electrodes using a dispersion-filtration-transfer procedure to assure the reproducibility of the deposits. After the electrochemical and morphological characterization of these WS2-COOH nanotube deposits, the formed biosensors showed very satisfying performance towards catechol detection with a linear range of 0.6-70 μmol L-1 and a sensitivity of 10.7 ± 0.2 mA L mol-1. The apparent Michaelis Menten constant of this system is slightly lower than the KM value of tyrosinase in solution, reflecting an excellent accessibility of the active site of the enzyme combined with a good mass transport of the target molecule through the deposit. For dopamine detection, we observed an accumulation of this substrate due to electrostatic interactions between the amine function of dopamine and the carboxylic acid groups of the nanotubes. This led to improved signal capture at low dopamine concentrations. With linear ranges of 0.5-10 μmol L-1 and 10-40 μmol L-1, and respective sensitivities of 6.2 ± 0.7 mA L mol-1 and 3.4 ± 0.4 mA L mol-1, the overall sensor performance is within the average of comparable results using carbon nanotubes. Nonetheless, the simplified handling of these nanotubes and their reduced environmental impact make these WS2-COOH nanotubes a promising nanomaterial for biosensing applications.

A homemade gold electrode is modified with a carbon nanotubes/gold nanoparticles nanocomposite to perform selective and sensitive electrochemical detection of dengue toxin. This nanostructured composite offers a large specific surface and a reactive interface allowing the immobilization of biological material. Dengue antibodies are immobilized on gold nanoparticles via covalent bonding for dengue toxin detection. The porous tridimensional network of carbon nanotubes and gold nanoparticles enhances the electrochemical signal and the overall performance of the sensor. After optimization, the system exhibits a high sensitivity of − 0.44 ± 0.01 μA per decade with wide linear range between 1 × 10−12 and 1 × 10−6 g/mL at a working potential of 0.22 V vs Ag/AgCl. The extremely low detection limit (3 × 10−13 g/mL) ranks this immunosensor as one of the most efficient reported in the literature for the detection of recombinant viral dengue virus 2 NS1. This biosensor also offers good selectivity, characterized by a low response to various non-specific targets and assays in human serum. The outstanding performances and the reproducibility of the system place the biosensor developed among the best candidates for future medical applications and for early diagnosis of dengue fever. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00604-020-04339-y) contains supplementary material, which is available to authorized users.

International audience; Engineering bioelectronic components and set-ups that mimic natural systems is extremely challenging. Here we report the design of a protein-only redox film inspired by the architecture of bacterial electroactive biofilms. The nanowire scaffold is formed using a chimeric protein that results from the attachment of a prion domain to a rubredoxin (Rd) that acts as an electron carrier. The prion domain self-assembles into stable fibres and provides a suitable arrangement of redox metal centres in Rd to permit electron transport. This results in highly organized films, able to transport electrons over several micrometres through a network of bionanowires. We demonstrate that our bionanowires can be used as electron-transfer mediators to build a bioelectrode for the electrocatalytic oxygen reduction by laccase. This approach opens opportunities for the engineering of protein-only electron mediators (with tunable redox potentials and optimized interactions with enzymes) and applications in the field of protein-only bioelectrodes.

The natural biodegradabilty of porous silicon (pSi) in physiological media limits its wider usage for implantable systems. We report the stabilization of porous silicon (pSi) membranes by chemical surface oxidation using RCA1 and RCA2 protocols, which was followed by a PEGylation process using a silane-PEG. These surface modifications stabilized the pSi to allow a long period of immersion in PBS, while leaving the pSi surface sufficiently hydrophilic for good filtration and diffusion of several biomolecules of different sizes without any blockage of the pSi structure. The pore sizes of the pSi membranes were between 5 and 20 nm, with the membrane thickness around 70 μm. The diffusion coefficient for fluorescein through the membrane was 2 × 10−10 cm2 s−1, and for glucose was 2.2 × 10−9 cm2 s−1. The pSi membrane maintained that level of glucose diffusion for one month of immersion in PBS. After 2 months immersion in PBS the pSi membrane continued to operate, but with a reduced glucose diffusion coefficient. The chemical stabilization of pSi membranes provided almost 1 week stable and functional biomolecule transport in blood plasma and opens the possibility for its short-term implantation as a diffusion membrane in biocompatible systems.

A high performance impedimetric immunosensor for the dengue virus antibody detection is presented. The setup profits from the formation of controlled and reproducible carbon nanotube (CNT) deposits on electrodes. Their easy functionalization via electrogeneration of a polypyrrole-NHS (N-hydroxysuccinimido 11-(pyrrol-1-yl) undecanoate) film enables the immobilization of the Dengue Virus 2 NS1 glycoprotein, the receptor unit, on the porous CNT layer via covalent amide coupling to provide the necessary selectivity towards Dengue NS1 antibody. All building steps of this immunosensor and the performance of this system were monitored by impedance spectroscopy and cyclic voltammetry. The resulting impedimetric dengue biosensor was tested in bovine blood plasma in addition to conventional measurements under controlled environment. After optimization, this immunosensor shows a good linearity in a wide concentration range (10−13–10−5 g mL−1).

An original impedimetric immunosensor was developed based on carbon nanotube (CNT) deposits with controlled thicknesses for enhanced electroactive surface areas leading to improved sensor performances. Cholera monitoring was chosen as the model immune system for this setup. These CNT deposits were characterized using confocal laser microscopy and electrochemical methods. To form the sensor device, the CNT deposits were functionalized via electrocoating of polypyrrole-nitrilotriacetic acid (poly(pyrrole-NTA)) followed by the formation of a Cu (II) complex with the NTA functions. The bioreceptor unit, cholera toxin B Subunit, modified with biotin, was then immobilized via coordination of the biotin groups with the NTA-Cu(II) complex. Each step of the formation of the immunosensor and the subsequent binding of the analyte antibody anti-cholera toxin were investigated with cyclic voltammetry and Electrochemical Impedance Spectroscopy. After optimization, the resulting impedimetric cholera sensor shows excellent reproducibility, increased sensitivities, a very satisfying detection limit of 10−13 g mL−1 and an exceptional linear range for anti-cholera detection of 8 orders of magnitude (10−13–10−5 g mL−1) and a sensitivity of 24.7 ± 0.4 Ω per order of magnitude.

900- and 100-nm-diameter polystyrene beads were combined with electrogenerated photosensitive poly-[tris(4,4-bis(3-pyrrol-1-ylpropyloxy)bipyridinyl)ruthenium(II)], (poly-[RuII-pyrrole]), metallopolymer on glassy carbon electrodes. Nanosphere lithography (NSL) with 900-nm-diameter microbead mask affords the realization of a nanostructured polymer (after dissolution of the polystyrene templates) with a typical highly-organized honeycomb nanostructure. NSL with 100-nm-diameter-nanobead mask allowed the achievement of a highly macroporous metallopolymer. The nanostructured Ru(II)-based metallopolymer was characterized by 3D laser scanning confocal microscopy and scanning electron microscopy (SEM). Electrochemical and photoelectrochemical studies demonstrate the enhancement of redox probe diffusion in the polymer layer for nanopatterned poly-[RuII-pyrrole]. This is accompanied with photocurrent enhancement for nanostructured polymer, especially in the case of poly-[RuII-pyrrole] obtained by the 100 nm-nanobead NSL. Keywords: Nanosphere lithography, Ruthenium complexes, Electropolymerization, Metallopolymers, Photoelectrochemistry

A photoelectrode was designed by electrodeposition of a pyrrole monomer modified with a polypyridyl Ru(II) complex bearing benzo[i]dipyrido-[3,2-a:2′.3′-c]phenazine (dppn) ligand. Owing to the intercalating properties of these immobilized complexes towards DNA double helix, cocaine aptamer was immobilized on the modified electrodes thanks to its stem-loop configuration in order to design a photoelectrochemical cocaine aptasensor. Especially using a double-fragment aptamer strategy, the binding of cocaine and the formation of the aptamer/cocaine complex was successfully observed and modeled by a Langmuir-Freundlich isotherm, giving access to an apparent dissociation constant K d of 3.8 mmol L −1 . The photoelectrochemical aptasensor exhibits a LOD of 10 nmol L −1 and linear range of 1 10 −8 –5 10 −4 mol L −1 .

International audience; This paper reports the development and optimisation of a glucose/O-2 biofuel cell. At the anode, the glucose oxidation was performed by glucose oxidase (GOx) co-immobilised with a phenanthrenequinone mediator. At the cathode, the catalysis of O-2 using tetrathiafulvalene and polyphenol oxidase (PPO) has been demonstrated for the first time. The open circuit voltage (OCV) of the optimised biofuel cell reached 0.32 V, and the maximum power density achieved was 40.811 mu W cm(-2) at 0.2 V. This original new GBFC showed quasi-stability in both OCV and power density for more than 25 days.

An electrochemical highly sensitive aptasensor was developed based on electropolymerized poly(pyrrole-nitrilotriacetic) acid film and a new aptamer functionalized by a pentahistidine peptide for the quantification of bisphenol A. A surface coverage of antibisphenol A aptamer of 1.84 × 10(-10) mol cm(-2) was estimated from the electrochemical signal of the [Ru(III)(NH3)6](3+) complex bound by electrostatic interactions onto the aptamer-modified electrode. The binding of bisphenol A onto the polymer film was successfully characterized by electrochemical methods as square wave voltammetry and electrochemical impedance spectroscopy measurements. The designed label-free impedimetric aptasensor displayed a wide linear range from 10(-11) to 10(-6) mol L(-1) with a sensitivity of 372 Ω per unit of log of concentration and an excellent specificity toward interfering agents such as 4,4'-dihydroxybiphenyl and bisphenol P.

International audience; We report on an alternative concept of biofuelcell functioning based on the unconventional use of enzymes to create apH difference generating a potential difference between electrodes soaked in quinhydrone solutions. The electrode and quinhydrone solution were confined in a dialysis bag placed into a compartment containing either glucose oxidase and catalase for the biocathode or urease for the bioanode. In presence of 0.4 mol L−1 glucose and urea, the enzyme reactions generate apH difference of 3.55, both compartments being separated by an agar-agar wall. The resulting biofuelcell exhibits an open-circuit voltage and maximum power of 208 mV and 30.6 μW, respectively, without immobilization and electrical connection of the involved enzymes. In addition, this biofuelcell was able to provide continuously10 μA during 23 h, producing 0.133 J and 0.828 C. A similar biofuelcell configuration based only on dialysis bags was also developed. A graphite disk electrode elaborated by mechanical compression of graphite particles and quinhydrone, was placed in a dialysis bag itself confined into another dialysis bag containing enzyme solution. The resulting power and open-circuit voltage at saturating substrate conditions are 7.6 μW and 157 mV, respectively.

A novel and simple immobilization strategy for biotinylated biological macromolecules onto electropolymerized poly(pyrrole-nitrilotriacetic acid)(NTA)–Cu2+ films without avidin as connecting bridge is reported. After complexation of Cu2+ by the polymerized NTA chelator, biotinylated biomolecules were immobilized by coordination of the biotin groups on the NTA–Cu2+ complex. The anchoring of biotinylated glucose oxidase was demonstrated by fluorescent characterization via FITC-labeled avidin and amperometric measurement of glucose. The resulting calibration curve led to a sensitivity and maximum current density values of 0.6 mA mol−1L cm−2 and 13.2 μA cm−2, respectively. Thus, biotinylated polyphenol oxidase was fixed leading to a catechol sensor with a sensitivity of 656 mA mol−1L cm−2 and maximum current density of 25.4 μA cm−2. This system was also applied to the efficient immobilization of biotinylated DNA, illustrated by impedimetric detection of the formation of the DNA duplex. Keywords: Biosensor, Avidin–biotin, Polypyrrole, Nitrilotriacetic acid

This paper describes the construction of an impedimetric immunosensor for the label-free detection of ciprofloxacin, an antibiotic belonging to synthetic fluoroquinolones. A poly(pyrrole-N-hydroxysuccinimide) film was electrogenerated onto electrodes and then used for the reagentless covalent binding of a fluoroquinolone model bearing an amino group. The resulting electrodes were utilized to immobilize a layer of anticiprofloxacin antibody onto the polymer surface by immunoreaction. In presence of ciprofloxacin, the antibody was displaced in solution inducing marked changes in the impedance of the sensor electrodes. These phenomena were detected and characterized by electrochemical impedance spectroscopy allowing the selective detection of extremely low ciprofloxacin concentration, namely, 1 x 10(-12) g mL(-1) or 3 pmol L(-1). Sensors exposed to ciprofloxacin showed a decrease in the sum of the interfacial resistances with the increase in ciprofloxacin concentration from 1 x 10(-12) to 1 x 10(-6) g mL(-1).

7 pages, 6 figures.-- PMID: 17826084 [PubMed].-- Printed version published on Nov 30, 2007., Impedance spectroscopy approaches combined with the immunosensor technology have been used for the determination of trace amounts of ciprofloxacin antibiotic belonging to the fluoroquinolone family. The sensor electrode was based on the immobilization of anti-ciprofloxacin antibodies by chemical binding onto a poly(pyrrole-NHS) film electrogenerated on a solid gold substrate. The electrode surface was modified by electropolymerization of pyrrole-NHS, antibody grafting and ciprofloxacin immunoreaction. The sensitive steps of surface modification, cyclic voltammetry (CV) and atomic force microscopy (AFM) imaging have been used for electrode surface characterization., The immunoreaction of ciprofloxacin on the grafted anti-ciprofloxacin antibody directly triggers a signal via impedance spectroscopy measurements which allows the detection of extremely low concentration of 10 pg/ml ciprofloxacin., The authors thank the Commission of the European Communities Research Directorate for their support in the framework of the ELISHA project no. NMP-A-CT-2003-505485-1. Drs. S. Cosnier, C. Martelet and N. Jaffrezic-Renault would like to thank the GDR CNRS 2619 “Microbiocapteurs” for partial support. Work performed at AMRg-CSIC was partially funded by the Spanish Ministry of Education and Science (contract numbers AGL2005-07700-C06-01). The AMR group is a consolidated Grup de Recerca de la Generalitat de Catalunya and has support from the Departament d’Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya (expedient 2005SGR 00207).

In order to determine the best kind of matrix that enables preservation of the enzymatic and electro-enzymatic activity of immobilized enzyme and provides accessibility towards substrate, various host materials (electropolymerized polypyrrole films, alginate polysaccharide, biocompatible synthetic latex and inorganic clays (laponite and layered double hydroxides LDHs), differing in permeability, ion exchange properties and hydrophobic–hydrophilic character, were compared for the fabrication of amperometric glucose biosensors. The electrochemical assays were performed by potentiostating the enzyme electrodes at 0.6 V vs. Ag/AgCl in order to oxidize the hydrogen peroxide enzymatically generated in the presence of glucose and oxygen. The highest sensitivity and maximum current density were recorded for laponite (82.3 mA M− 1 cm− 2 and 410 μA cm− 2 respectively) and LDHs (55 mA M− 1 cm− 2 and 417 μA cm− 2, respectively).

The construction of amperometric immunosensors to cholera antitoxin immunoglobulins were shown to have improved sensitivity when the cholera toxin B subunit biorecognition entity was linked to an electrogenerated biotinylated polypyrrole film copolymerized with pyrrole-lactobionamide monomer. The copolymer exhibits greater film permeability than biotinylated polypyrrolic or polyphenolic films for the permeation of electroactive species. Hence, when the presence of the HRP marker of the immunoassay was determined using hydroquinone, the production of electroactive quinone was shown to permeate faster to the electrode, thus providing a faster response time.

The electrochemical properties of a new Co(II) deuteroporphyrin substituted by two electropolymerizable pyrrole groups has been investigated in organic solvent. This functionalization has allowed the preparation of the first example of a cobalt deuteroporphyrin film by oxidative electropolymerization. The resulting conducting polypyrrole film exhibits the regular electroactivity of cobalt deuteroporphyrin. Compared to conventional cobalt porphyrin electrochemistry, the replacement of porphyrin macrocycle by deuteroporphyrin ring results in markedly more negative potential values for the metal-centered oxidation and reduction processes. The influence of NO 2- as axial ligand on the reductive behavior of the electropolymerized cobalt (II) deuteroporphyrin is examined. The recognition properties of the film illustrated by the potentiometric shift of the Co(II)/(I) reduction were exploited for the determination of NO 2- in the concentration range 2 10 -6 - 2.5 10 -4 M. Keywords

We describe herein, the electrochemical properties of an hydroporphyrin of Ni(II) substituted by two pyrrole groups in organic media (THF and CH2Cl2). In the anodic region it has been shown that the electrochemical behaviour of this complex investigated by cyclic voltammetry and coulometry coupled with UV–visible spectroscopy is strongly dependent on the nature of the solvent.Furthermore, the electrochemical oxidation of the pyrrrole groups has led to the first example of an electrogenerated polypyrrole–metallochlorin film. The resulting modified electrodes exhibit the same electrochemical properties as the monomer free in solution. Preliminary experiments have also demonstrated the possibility to study electrochemically this polymeric film in CH3CN contrary to the Ni(II) chlorin, which is insoluble in this medium. Keywords: Ni(II) hydroporphyrins, Modified electrodes, Electropolymerization, Polypyrrole

The design of photoactive functionalized electrodes for the sensitive transduction of double-stranded DNA hybridization is reported. Multifunctional complex [Ru(bpy-pyrrole)2 (dppn)](2+) (bpy-pyrrole=4-methyl-4'-butylpyrrole-2,2'-bipyridine, dppn=benzo[i]dipyrido[3,2-a:2',3'-c]phenazine) exhibiting photosensitive, DNA-intercalating, and electropolymerizable properties was synthesized and characterized. The pyrrole groups undergo oxidative electropolymerization on planar electrodes forming a metallopolymer layer on the electrode. Thanks to the photoelectrochemical and intercalating properties of the immobilized Ru(II) complex, the binding of a double-stranded HIV DNA target was photoelectrochemically detected on planar electrodes. Photocurrent generation through visible irradiation was correlated to the interaction between double-stranded DNA and the metallointercalator polymer. These interactions were well fitted by using a Langmuir isotherm, which allowed a dissociation constant of 2×10(6) L mol(-1) to be estimated. The low detection limit of 1 fmol L(-1) and sensitivity of 0.01 units per decade demonstrate excellent suitability of these modified electrodes for detection of duplex DNA.

The electrochemical immobilization of salicylate hydroxylase (SH) within poly(amphiphilic pyrrole ammonium) films electrogenerated on carbon electrode is described. The amperometric determination of salicylate is carried out at 0.4 V (vs. Ag/AgCl) via the oxidation of the enzymically generated catechol. The detection limit and the sensitivity of the polypyrrole-SH electrode were 3×10−9 M and 1.7 A M−1 cm−2, respectively. Moreover, the co-entrapment of SH and polyphenol oxidase (PPO) in such polypyrrole films provides a bienzyme electrode also for the determination of salicylate. Contrary to the monoenzyme electrode, the functioning principle of the bienzyme electrode is based on the reduction of o-quinone enzymically generated from catechol. Consequently, the amperometric detection of salicylate was performed at −0.2 V without interferences from easily oxidizable compounds. The calibration range for salicylate measurement and the biosensor sensitivity were 5×10−8–3×10−6 M and 0.25 A M−1 cm−2, respectively.

The functionalization of microelectrodes has been carried out by oxidative polymerization of a biotinyl pyrrole monomer in acetonitrile. The resulting biotinylated polymer was used for the simple and reagentless anchoring of avidin and biotinylated enzymes via avidin-biotin bridges. Thus, the immobilization of five layers of glucose oxidase was performed on various platinum electrodes (surfaces: 0.165 and 0.448 mm2). The amperometric response of the microbiosensors to glucose was recorded at 0.6 V vs Ag/AgCl and the analytical performances (sensitivity and I max) were proportional to the microelectrode surface. In addition, the immobilization of four and seven layers of polyphenol oxidase on carbon fiber microelectrodes (diameter 8 μm) has led to amperometric biosensors for catechol exhibiting analytical characteristics proportional to the number of enzyme layers. Moreover, these two kinds of microbiosensor present apparent K M values similar to those determined for the free enzymes in bulk solution.

Electrochemical impedance spectroscopy was evaluated for the label free detection of MCF-7 cancer cell in which c-erbB-2 receptor is overexpressed on the cell surfaces. Anti-c-erbB-2, used as a specific antibody, was immobilized on electrogenerated polypyrrole-NHS on electrodes via covalent linking. The polymer formation, the grafting of the antibody, and the recognition event with the cancer cells using MCF-7 as a model cell line, were characterized by using cyclic voltammetry and fluorescence microscopy. The impedimetric sensor showed high sensitivity from 100 to 10 000 cell/mL without needing any labeling step and represents an efficient transduction method for cell selective detection. Keywords: Immunosensors, Anti c-erbB-2, Cell detection, Electrochemical impedance spectroscopy (EIS), Surface modification

New Cu (II), Mn (III) and Fe (III) deuteroporphyrins functionalized by two electropolymerizable pyrrole groups have been synthesized. The electrooxidation of these metallodeuteroporphyrins has allowed the formation of conducting polypyrrole films exhibiting electrochemical behavior identical to that of the corresponding monomers. In addition, the efficient immobilization of metallodeuteroporphyrins was corroborated by spectrophotometric measurements. Moreover, the potential electrocatalytic properties of Mn (III)-based polypyrrole films in the presence of dioxygen and benzoic anhydride have been illustrated by cyclic voltammetry. Furthermore, the recognition properties of Fe (III)-based polypyrrole films have been highlighted with cyanide in organic electrolyte. Preliminary experiments have also demonstrated the feasibility of such recognition processes in aqueous media.

The concept and potentialities of two original electrochemical procedures of enzyme immobilization based on functionalized polypyrroles are described. A two-step method consists of the adsorption of aqueous amphiphilic pyrrole monomerenzyme mixtures on an electrode surface followed by electropolymerization of the adsorbed amphiphilic monomers. Example of multienzyme entrapment and copoiymer elaboration as well as electrical wiring of immobilized enzymes are presented. The second method is based on the electropolymerization of a pyrrole-modified biotin. The resulting polymer was successfully used for successive attachment of avidin and biotinylated enzymes.

A new biotin derivative functionalized by a pyrrole group has been synthesized. This functionalization has allowed the preparation of the first example of a poly(pyrrole-biotin) film by oxidative polymerization. In addition, the successful copolymerization of a polypyridinyl complex of ruthenium(II) containing pyrrole groups with the biotin derivative provided redox copolymers exhibiting specific adsorption sites. The resulting copolymer electrodes were applied to the immobilization of a biotinylated glucose oxidase through an avidin bridge. An avidin-conjugated alkaline phosphatase was also immobilized by direct specific adsorption onto the biotinylated polymer. The amperometric response of the resulting biosensors to glucose and phenylphosphate has been studied.

The electropolymerization of an alkaline phosphatase (AP)−amphiphilic pyrrole ammonium mixture previously adsorbed on the electrode surface provides efficient entrapment of AP in a polypyrrole film. The resulting biosensor was applied to the detection of phenyl phosphate via amperometric oxidation at 0.6 V vs SCE of the enzymically generated phenol. The sensitivity and detection limit of the biosensor were 862 μA M-1 cm-2 and 20 μM, respectively. The co-immobilization of polyphenol oxidase and AP leads to a bienzyme electrode for the determination of phenyl phosphate on the basis of amperometric detection of the enzymically generated o-quinone at −0.2 V. An amplification factor of 9.7 was calculated as the ratio of the bienzyme to monoenzyme electrode sensitivities. In the presence of 5 mM MgCl2, the sensitivity and detection limit of the biosensor for phenyl phosphate were 36.82 mA M-1 cm-2 and 0.2 μM, respectively. Phosphate competitively inhibited the hydrolysis of phenyl phosphate. Consequently, its d...

Reference LPI-ARTICLE-1997-022View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Cross-linked poly(ethylene oxide) (PEO) networks were proposed as internal reference systems for Na+ and Li+ ion selective electrodes with NASICON type ceramics as the sensitive membrane and for pH electrodes. The cross-linking significantly improves the bulk ionic conductivity of the polymers at room temperature as well as the interfacial electrical properties. It increases the long term stability of the all-solid-state electrode.

This paper reports on the impedimetric transduction of binding reaction between polymerized saccharides and target lectins. The controlled potential electro-oxidation of pyrrole-lactosyl and pyrrole-3’-sialyllactosyl at 0.95 V vs Ag/AgCl, provides thin and reproducible poly(pyrrole-saccharide) films. The affinity binding of two lectins: Arachis hypogaea, (PNA) and Maackia amurensis (MAA) onto poly(pyrrole-lactosyl) and poly(pyrrole-3’-sialyllactosyl) electrodes, was demonstrated by cyclic voltammetry in presence of ruthenium hexamine and hydroquinone. In addition, rotating disk experiments were carried out to determine the permeability of both polypyrrole films and its evolution after incubating with lectin target. Finally, the possibility of using the poly(pyrrole-lactosyl) or poly(pyrrole-3’-siallyllactosyl) films for the impedimetric transduction of the lectin binding reaction, was investigated with hydroquinone (2×10-3 mol L-1) as a redox probe in phosphate buffer. The resuting impedance spectra were interpreted and modeled as an equivalent circuit indicating that charge transfer resistance (Rct) and relaxation frequency (f°) parameters are sensitive to the lectin binding. Rct increases from 77 to 97 Ω cm2 for PNA binding and from 93 to 131 Ω cm2 for MAA binding. In parallel, f° decreases from 276 to 222 Hz for PNA binding and from 223 to 131 Hz for MAA binding. This evolution of both parameters reflects the steric hindrances generated by the immobilised lectins towards the permeation of the redox probe.

5 pages; International audience; We describe the first implanted glucose biofuel cell (GBFC) that is capable of generating sufficient power from a mammal's body fluids to act as the sole power source for electronic devices. This GBFC is based on carbon nanotube/enzyme electrodes, which utilize glucose oxidase for glucose oxidation and laccase for dioxygen reduction. The GBFC, implanted in the abdominal cavity of a rat, produces an average open-circuit voltage of 0.57 V. This implanted GBFC delivered a power output of 38.7 μW, which corresponded to a power density of 193.5 μW cm(-2) and a volumetric power of 161 μW mL(-1). We demonstrate that one single implanted enzymatic GBFC can power a light-emitting diode (LED), or a digital thermometer. In addition, no signs of rejection or inflammation were observed after 110 days implantation in the rat.

We report the design of a novel glucose/O2 biofuel cell (GBFC) integrating carbon nanotube-based 3D bioelectrodes and using naphthoquinone-mediated oxidation of glucose by glucose oxidase and direct oxygen reduction by laccase. The GBFCs exhibit high open circuit voltages of 0.76 V, high current densities of 4.47 mA cm(-2), and maximum power output of 1.54 mW cm(-2), 1.92 mW mL(-1) and 2.67 mW g(-1). The GBFC is able to constantly deliver 0.56 mW h cm(-2) under discharge at 0.5 V, showing among the best in vitro performances for a GBFC. Using a charge pump, the GBFC finally powered a Light Emitting Diode (LED), demonstrating its ability to amplify micro watts to power mW-demanding electronic devices.

A label-free and highly sensitive impedimetric aptasensor was developed based on electropolymerized film for the determination of thrombin. The first step is the electrogeneration of a poly(pyrrole-nitrilotriacetic acid) (poly(pyrrole-NTA)) film onto the surface of electrodes followed by complexation of Cu(2+) ions. Then, the histidine labeled thrombin aptamer was immobilized onto the electrode through coordination of the histidine groups on the NTA-Cu(2+) complex. The aptamer sensor was applied for the detection and quantification of thrombin via impedimetric detection without a labeling step. A linear quantification of thrombin was obtained in the range 4.7×10(-12)-5.0×10(-10) mol L(-1) with a sensitivity of 2838 Ω/log unit (R(2)=0.9984). The impedance modulus at 0.3 Hz as a function of thrombin concentration was used to elaborate a similar linear relationship from 4.7×10(-12) to 5×10(-10) mol L(-1). In addition, aptamer-poly(pyrrole-NTA) electrodes incubated for 40 min in aqueous solutions of bovine serum albumin (BSA), lysozyme and IgG (5×10(-7) mol L(-1)) did not exhibit non-specific adsorption of proteins. Moreover, it has been demonstrated that the selective sensor can be regenerated several times with a good reproducibility.

For four decades, the development of biointerfaces has been the subject of increasing research efforts in the field of biosensors and energy conversion. Owing to their high conductivity, inertness and electroactive surface area, graphene and carbon nanotube are widely used for the design of biosensors and their functionalization was successfully performed by electrogenerated polymers exhibiting affinity or covalent binding interactions towards biomolecules. Recent examples of electropolymerized films will be presented for the design of labeless immunosensors and aptasensors for bisphenol A, cocaine, dengue antibody or cholera toxin antibody [1]. We report thus the synthesis and electrochemical characterization of a novel electropolymerizable Ru(II) complex bearing an intercalator group as well as the electrochemical behavior and photoelectrochemical properties of the resulting polymer film [2]. The latter was applied to the label-free photoelectrochemical detection of cocaine. A photoelectrode was thus designed by electrodeposition of a pyrrole monomer modified with a polypyridyl Ru(II) complex bearing benzo[i]dipyrido-[3,2-a:2’.3’-c]phenazine (dppn) ligand. Owing to the intercalating properties of these immobilized complexes towards DNA double helix, cocaine aptamer was immobilized on the modified electrodes thanks to its stem-loop configuration in order to design a photoelectrochemical cocaine aptasensor. The detection of cocaine via the formation of the aptamer/cocaine complex was successfully observed via a decrease in the photocurrent intensity. The photoelectrochemical aptasensor exhibits a detection limit of 10 nmol L-1 and linear range of 1 10-8 to 5 10-4 mol L-1 [3]. We report here the original synthesis of an anti-bisphenol A (BPA) aptamer conjugated at its 5’-end with a pentahistidine peptide and its use for the design of an impedimetric BPA aptasensor. The introduction of a histidine tag is dedicated to the non-covalent binding of the aptamer onto electrodes previously modified by polypyrrole nitrilotriacetic films. The aptamer immobilization occurs via the histidine axial ligation onto Cu complex chelated by the polypyrrole film. This immobilization method, already used by our group to elaborate immunosensors or DNA sensors, offers a close proximity at the molecular level between the immobilized probe and the modified electrode surface. This approach thus confers a high sensitivity to the detection process, namely the aptamer/BPA folding. The resulting labeless impedimetric aptasensor displays a wide linear range from 10-11 to 10-6 mol L-1 with a sensitivity of 26 W cm2 per decade and an excellent specificity towards interfering agents such as 4,4'-dihydroxybiphenyl and bisphenol P. With the aim to improve the sensitivity of impedimetric biosensors, we have investigated the influence of a multiwalled carbon nanotube (MWCNT) coating and its thickness on the impedimetric transduction. We present thus a reliable procedure based on dispersion and filtration of MWCNT forming homogeneous films with controlled thicknesses and morphologies, which can easily be transferred on electrode surfaces. Polypyrrole-NTA films were electrogenerated on MWCNT modified glassy carbon electrode to immobilize biotinylated cholera toxin via the coordination of the biotin group onto Cu2+ complex chelated on the polymerized NTA groups. Concerning the design of this immunosensor, different thicknesses of carbon nanotube films were tested. For this purpose, three different volumes of CNT suspension solutions were filtered on a cellulose filter and then transferred to the electrode surface for modification of the three different thickness films by electropolymerization and post-biofunctionalization. The resulting impedimetric immunosensor for cholera toxin antibody, shows excellent reproducibility, increased sensitivities, and an exceptional linear range for antibody detection between 0.1 pg.mL-1 to 1 mg.mL-1. Similar results were obtained for the detection of Dengue antibody, namely a detection limit of 0.1 pg.mL-1. References F. Cecchini, L. Fajs, S. Cosnier, R. S. Marks, Trends in analytical chemistry, in press F. Haddache, A. Le Goff, B. Reuillard, K. Gorgy, C. Gondran, N. Spinelli, E. Defrancq, S. Cosnier, Chem. Eur. J. 2014, 20, 15555-15560. F. Haddache, A. Le Goff, N. Spinelli, P. Gairola, K. Gorgy, C. Gondran, E. Defrancq, S. Cosnier, Anal. Chem., submitted.

We describe herein the fabrication of bioelectrodes by compression of a mixture of graphite particles, enzyme and redox mediator that leads to the immobilization and electrical connection of enzymes. Bioanodes were elaborated by combining graphite with glucose oxidase and ferrocene while biocathodes resulted from the association of graphite, laccase and ABTS. The influence of the enzyme loading on the electrocatalytic properties of bioelectrodes for glucose oxidation and oxygen reduction was examined and an optimum enzyme loading was determined: 5% (w/w). The modulation of the mediator loading led to optimum compositions of 45 and 50% for ABTS and ferrocene, respectively. A biofuel cell configuration was assembled and its performances were investigated as a function of pH providing, at pH 6, a maximum power density and an open circuit voltage of 207 μW cm −2 and 450 mV, respectively.

International audience; Reaction of dimeric [Rh(II)(2)(phen)(2)(μ-OAc)(2)(MeCN)(2)](BF(4))(2) (phen =1,10-phenanthroline) with pyrazine (pz) in a 1:2 ratio leads to the new 1-D metal-metal-bonded coordination oligomer {[Rh(II)(2)(phen)(2)(μ-OAc)(2)(pz)](BF(4))(2)}(n) (Rh-Rhpz)(n) (1), where each Rh atom of the dimeric unit (Rh-Rh) is coordinated in the equatorial plane to a nitrogen atom of a rigid and linear bifunctionalized organic linker (pz). Single X-ray diffraction analysis reveals the 1-D straight oligomeric chain structure (molecular wire, MW) consists of alternating (Rh-Rh) units and pz linking ligands with free BF(4)(-) as counteranions, and each metal center has a slightly distorted octahedral arrangement. The presence of accessible labile MeCN groups on both ends of these MWs ("free ends") enables functionalization of a 4-mercaptopyridine-gold coordinating platform (Au/MP) to form in one step a layer of coordination oligomer (Au/MP(Rh-Rhpz)(n); n ≈ 50). Furthermore (Rh-Rhpz)(n) (n = 1-6) MWs were grafted to Au/MP surfaces by a conventional step-by-step assembly construction involving coordination reactions between the Rh dimer ([Rh(2)(phen)(2)(μ-OAc)(2)(MeCN)(2)](BF(4))(2) (2)) and pz. A detailed physicochemical study (UV-vis, RAIR, QCM-D, ellipsometry, contact angle measurements, as well as impedance spectroscopy and cyclic voltammetry) has been made during both assembly methods to characterize the resulting surface-anchored coordination molecular wire (CMW) layers (Au/MP(Rh-Rhpz)(n)). The results indicate that the immobilized molecular assemblies (MAs) were successfully fabricated using both methods of assembly. The efficiency of the two methods is discussed.

Biotinylated amphipol was used to entrap FhuA (an E. coli outer membrane protein) and immobilize the FhuA-amphipol complex on streptavidin surfaces. Using this assembly, we have successfully devised surface-based assays for studying the recognition of FhuA by pb5 (a bacteriophage T5 protein) and determination of the affinity constant.

Enzymatic fuel cells use enzymes to produce energy from bioavailable substrates. However, such biofuel cells are limited by the difficult electrical wiring of enzymes to the electrode. Here we show the efficient wiring of enzymes in a conductive pure carbon nanotube matrix for the fabrication of a glucose biofuel cell (GBFC). Glucose oxidase and laccase were respectively incorporated in carbon nanotube disks by mechanical compression. The characterization of each bioelectrode shows an open circuit potential corresponding to the redox potential of the respective enzymes, and high current densities for glucose oxidation and oxygen reduction. The mediatorless GBFC delivers a high power density up to 1.3 mW cm−2 and an open circuit voltage of 0.95 V. Moreover, the GBFC remains stable for 1 month and delivers 1 mW cm−2 power density under physiological conditions (5×10−3 mol l−1 glucose, pH 7). To date, these values are the best performances obtained for a GBFC., Glucose biofuel cells can be used to produce clean energy from renewable sources, but their use is limited by poor stability and low power output. In this study, bioelectrodes are fabricated using carbon nanotubes and the resulting biofuel cells have improved stability and power.

Tethered bilayer lipid membranes (tBLMs) are designed on mixed self-assembled monolayers (SAMs) of a novel synthetic anchoring thiol, 2,3-di-o-palmitoylglycerol-1-tetraethylene glycol mercaptopropanoic acid ester (TEG-DP), and a new short dilution thiol molecule, tetraethylene glycol mercaptopropanoic acid ester (TEG). tBLM formation was accomplished by self-directed fusion of small unilamellar vesicles of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. The influence of the dilution of the anchoring thiol molecule in the SAM on the vesicle fusion process and on the properties of the resulting tBLMs is studied. It is observed by quartz crystal microbalance that vesicle fusion is a one-step process for a pure TEG-DP SAM as well as for mixed SAMs containing a high concentration of the anchoring thiol. However, upon dilution of the anchoring thiol to moderate concentrations, this process is decelerated and possibly follows a pathway different from that observed on a pure TEG-DP SAM. Electrochemical impedance spectroscopy is used to qualitatively correlate the composition of the SAM to the electrical properties of the tBLM. In this paper we also delineate the necessity of a critical concentration of this anchoring TEG-DP thiol as a requisite for inducing the fusion of vesicles to form a tBLM.

Impedance spectroscopy transduction combined with the immunosensor technology has been used for the determination of atrazine, a herbicide The sensor electrode was based on the immobilization of anti-atrazine antibody by affinity binding onto a polypyrrole film N-substituted by nitrilotriacetic acid NTA electrogenerated on a gold electrode. The poly NTA film was previously modified by the coordination of Cu2 ions by the chelating NTA centers. The anti-atrazine antibody Fab fragment K47 modified with histidine-tag was then anchored by affinity interactions between the histidine-tag and the coordinated Cu2. Cyclic voltammetry experiments confirm that the antibody immobilization and the resulting immunosensor were applied to the impedimetric detection of atrazine without reagent and labelling step. The immunoreaction of atrazine on the attached anti-atrazine antibody directly triggers an increase in the charge transfer resistance proportional to the atrazine concentration, allowing the detection of extremely low atrazine concentration, namely 10 pg mL−1.

We describe herein the synthesis and electrochemical polymerization of a viologen monomer functionalized by a biotin group and the use of its redox properties for the impedimetric sensing of protein binding. The electrochemical oxidation of the pyrrole group at 0.85 V in CH3CN led to a biotinylated polypyrrole film allowing the successive anchoring of an avidin layer and a biotinylated cholera toxin layer. EIS performed at −0.45 V/SCE without redox probe in solution showed the specific immobilization of the anti-cholera toxin antibody. Keywords: Viologen, Impedance, Polypyrrole, Biotin, Immunosensor

An ultrahigh performance impedimetric DNA sensor is presented showing detection limits in the femtomolar range. This electrochemical setup was constructed initially by electrogeneration of poly(11-pyrrol-1-yl-undecanoic acid N(alpha'),N(alpha)-bis(carboxymethyl)-L-lysine amide) (poly(pyrrole-NTA)) film. The latter was then modified by the coordination of Cu(2+) ions onto the chelating NTA centers followed by the immobilization of the ssHIV-DNA previously modified by a polyhistidine tag by affinity binding. The immobilization of the DNA probe and hybridization with the complementary target ssHIV-DNA were investigated using fluorescence microscopy and quantified with quartz crystal microbalance experiments leading to DNA probe and duplex coverage of 1.7 x 10(-11) and 7.7 x 10(-12) mol cm(-2), respectively. The duplex formation was corroborated by amperometric measurements through the duplex labeling by a glucose oxidase. In the presence of hydroquinone as redox indicator, the DNA sensor was applied to the impedimetric detection of target DNA without a labeling step. A linear quantification of the HIV DNA target was carried out in the range 10(-15) to 10(-8) mol L(-1).

International audience; Powering future generations of implanted medical devices will require cumbersome transcutaneous energy transfer or harvesting energy from the human body. No functional solution that harvests power from the body is currently available, despite attempts to use the Seebeck thermoelectric effect, vibrations or body movements. Glucose fuel cells appear more promising, since they produce electrical energy from glucose and dioxygen, two substrates present in physiological fluids. The most powerful ones, Glucose BioFuel Cells (GBFCs), are based on enzymes electrically wired by redox mediators. However, GBFCs cannot be implanted in animals, mainly because the enzymes they rely on either require low pH or are inhibited by chloride or urate anions, present in the Extra Cellular Fluid (ECF). Here we present the first functional implantable GBFC, working in the retroperitoneal space of freely moving rats. The breakthrough relies on the design of a new family of GBFCs, characterized by an innovative and simple mechanical confinement of various enzymes and redox mediators: enzymes are no longer covalently bound to the surface of the electron collectors, which enables use of a wide variety of enzymes and redox mediators, augments the quantity of active enzymes, and simplifies GBFC construction. Our most efficient GBFC was based on composite graphite discs containing glucose oxidase and ubiquinone at the anode, polyphenol oxidase (PPO) and quinone at the cathode. PPO reduces dioxygen into water, at pH 7 and in the presence of chloride ions and urates at physiological concentrations. This GBFC, with electrodes of 0.133 mL, produced a peak specific power of 24.4 microW mL(-1), which is better than pacemakers' requirements and paves the way for the development of a new generation of implantable artificial organs, covering a wide range of medical applications.