New Microfluidic System for Electrochemical Impedance Spectroscopy Assessment of Cell Culture Performance: Design and Development of New Electrode Material

Electrochemical impedance spectroscopy (EIS) is widely accepted as an effective and non-destructive method to assess cell health during cell-culture. However, there is a lack of compact devices compatible with microfluidic integration and microscopy that could provide the real-time and non-invasive monitoring of cell-cultures using EIS. In this paper, we reported the design and characterization of a modular EIS testing system based on a patented technology. This device was fabricated using easily processable methodologies including screen-printing of the impedance electrodes and molding or micromachining of the cell culture chamber with an easy assembly procedure. Accordingly, to obtain processable, biocompatible and sterilizable electrode materials that lower the impact of interfacial impedance on TEER (Transepithelial electrical resistance) measurements, and to enable concomitant microscopy observations, we optimized the formulation of the electrode inks and the design of the EIS electrodes, respectively. First, electrode materials were based on carbon biocompatible inks enriched with IrOx particles to obtain low interfacial impedance electrodes approaching the performances of classical non-biocompatible Ag/AgCl second-species electrodes. Secondly, we proposed three original electrode designs, which were compared to classical disk electrodes that were optically compatible with microscopy. We assessed the impact of the electrode design on the response of the impedance sensor using COMSOL Multiphysics. Finally, the performance of the impedance spectroscopy devices was assessed in vitro using human airway epithelial cell cultures

A disposable enzymatic biofuel cell for glucose sensing via short-circuit current

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Study of Genipin Behavior in Neutral and Acidic Aqueous Solutions at Elevated Temperatures

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Investigation of GOx Stability in a Chitosan Matrix: Applications for Enzymatic Electrodes

International audienceIn this study, we designed a new biosensing membrane for the development of an electrochemical glucose biosensor. To proceed, we used a chitosan-based hydrogel that entraps glucose oxidase enzyme (GOx), and we crosslinked the whole matrix using glutaraldehyde, which is known for its quick and reactive crosslinking behavior. Then, the stability of the designed biosensors was investigated over time, according to different storage conditions (in PBS solution at temperatures of 4 °C and 37 °C and in the presence or absence of glucose). In some specific conditions, we found that our biosensor is capable of maintaining its stability for more than six months of storage. We also included catalase to protect the biosensing membranes from the enzymatic reaction by-products (e.g., hydrogen peroxide). This design protects the biocatalytic activity of GOx and enhances the lifetime of the biosensor

Optimization of Laccase Adsorption-Desorption Behaviors on Multi-Walled Carbon Nanotubes for Enzymatic Biocathodes

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Glucose biofuel cell construction based on enzyme, graphite particle and redox mediator compression

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Hierarchical Structure of Gold and Carbon Electrode for Bilirubin Oxidase-Biocathode

Biofuel cells (BFCs) with enzymatic electrocatalysts have attracted significant attention, especially as power sources for wearable and implantable devices; however, the applications of BFCs are limited owing to the limited O2 supply. This can be addressed by using air-diffusion-type bilirubin oxidase (BOD) cathodes, and thus the further development of the hierarchical structure of porous electrodes with highly effective specific surface areas is critical. In this study, a porous layer of gold is deposited over magnesium-oxide-templated carbon (MgOC) to form BOD-based biocathodes for the oxygen reduction reaction (ORR). Porous gold structures are constructed via electrochemical deposition of gold via dynamic hydrogen bubble templating (DHBT). Hydrogen bubbles used as a template and controlled by the Coulomb number yield a porous gold structure during the electrochemical deposition process. The current density of the ORR catalyzed by BOD without a redox mediator on the gold-modified MgOC electrode was 1.3 times higher than that of the ORR on the MgOC electrode. Furthermore, the gold-deposited electrodes were modified with aromatic thiols containing negatively charged functional groups to improve the orientation of BOD on the electrode surface to facilitate efficient electron transfer at the heterogeneous surface, thereby achieving an ORR current of 12 mA cm−2 at pH 5 and 25 °C. These results suggest that DHBT is an efficient method for the fabrication of nanostructured electrodes that promote direct electron transfer with oxidoreductase enzymes

Optimization of Laccase Adsorption-Desorption Behaviors on Multi-Walled Carbon Nanotubes for Enzymatic Biocathodes

Laccase adsorption-desorption behaviors on the surface of multi-walled carbon nanotubes (MWCNTs) were investigated using spectrophotometry and voltammetry. The optimum condition for laccase adsorption is 5.0 mg/mL of laccase in 0.01 M phosphate-buffered saline (PBS) at pH 5.0. Laccase adsorption is a reversible phenomenon that is dependent upon the nature of MWCNTs and the concentration of ionic strength in the laccase solution. Chitosan was functionalized as a nanoporous reservoir to minimize laccase desorption. Chitosan was found to protect approximately 97.2% of the adsorbed laccase from MWCNTs during the first six hours of observation. The three-dimensional (3D) biocathode, MWCNTs-laccase-chitosan with a 0.2 cm2 geometric area, was shown to have a stable open circuit potential (OCP) of 0.55 V, a current density of 0.33 mA cm-2 at 0.2 V vs. saturated calomel electrode (SCE), and a stable current for 20 hours of successive measurements. This report provides a new insight into the study of a high-performance laccase-based biocathode via optimization of adsorption and minimization of desorption phenomena

Réacteur implantable biocompatible

The invention concerns a bioreactor obtained by compressing a mixture of an enzyme, a conductor and chitosan. The conductor can consist of carbon nanotubes. This bioreactor can be produced according to the following steps: preparing a mixture of powders in which the proportion of enzyme powder relative to a carbon nanotube powder is of the order of 50/50 by weight; preparing a viscous solution of chitosan in a ratio of 5 to 15 (in mg) of chitosan to 0.75 to 1.25 (in ml) of acetic acid diluted to 0.4 to 0.6% by volume in water; adding the viscous chitosan to the mixture of powders in a proportion be weight of 3 to 5 of powder to 5 to 10 of chitosan; carrying out a first compression followed by light grinding; carrying out a second compression to produce a pellet; and drying at ambient temperature.L'invention concerne un bioréacteur obtenu par compression d'un mélange d'une enzyme, d'un conducteur et de chitosane. Le conducteur peut être constitué de nanotubes de carbone. Ce bioréacteur peut être fabriqué selon les étapes suivantes : préparer un mélange de poudres dans laquelle la proportion de poudre d' enzyme par rapport à une poudre de nanotubes de carbone est de l'ordre de 50/50 en poids ; préparer une solution visqueuse de chitosane dans un rapport de 5 à 15 (en mg) de chitosane à 0,75 à 1,25 (en ml) d'acide acétique dilué à 0,4 à 0,6 % en volume dans de l'eau ; ajouter au mélange de poudres la chitosane visqueuse dans une proportion pondérale de 3 à 5 pour la poudre à 5 à 10 pour la chitosane ; procéder à une première compression puis à un broyage léger ; procéder à une deuxième compression pour réaliser une pastille ; et sécher à température ambiante

Surface energy and hybridization studies of amorphous carbon surfaces

International audienceSurface properties of a large number of amorphous carbon (a-C) films have been investigated using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Dense a-C surfaces with variable sp3/(sp2 + sp3) average hybridization were grown using sputtering or pulsed laser deposition (PLD) and were further chemically modified by thermal annealing, ion bombardment or covalent grafting of organic monolayers. The average carbon hybridization, impurity level and mass density, were deduced from XPS and photoelectron energy loss spectroscopy (PEELS). The depth sensitivity of the dispersive (Lifshitz-van der Waals) interaction, estimated at 1-2 nm from the dependence of γLW on the grafted perflorodecene molecule coverage, is much better than XPS which probes a 3-5 nm depth. The observation of a non-monotonic behavior in the correlation between surface hybridization and electron donor component of surface energy reveals that the average carbon hybridization alone does not describe the entire surface energy physics. The role of π bond clustering in the polar interactions is thus considered and some implications on surface reactivity and mutual interactions with molecular or biomolecular species are discussed