Development and optimization of the novel conductometric (bio)sensors based on natural zeolite for ammonium, urea and L-arginine determination

Le travail de la thèse présente une série de (bio)capteurs conductimétriques, à base de la clinoptilolite, pour la détermination de l’ammonium, de l’urée et de la L-arginine. La clinoptilolite, le matériau nanométrique, possédant des propriétés de la sorption intrinsèque et une capacité d’échange cationique vis-à-vis des espèces ammonium, a été d’abord utilisée pour la réalisation d’un microcapteur conductimétrique sélectif à NH4+. Ci-après, une application de ce nanomatériau dans les biocapteurs est favorable pour le fonctionnement dans les solutions tampons multicomposants. Parmi plusieurs variantes de biocapteurs à l’urée à base de la zéolite, la plus intéressante est le biocapteur, dans lequel la couche de la clinoptilolite, déposée sur le transducteur, a été recouverte par le dépôt de la couche de l’uréase et de la zéolite. Pour l’élaboration d’un biocapteur conductimétrique hautement sensible pour la détermination de la L-arginine, l’arginase et l’uréase ont été co-réticulées sur le transducteur. Une détermination quantitative de la L-arginine dans une solution buvable « Arginine Veyron » a montré un fort accord avec les données fournies par le producteur. Une procédure détaillée de l’optimisation du biocapteur conductimétrique pour la détection de la L-arginine dans le sérum bovin a été proposée. La clinoptilolite a été également appliquée comme un modificateur dans la co-immobilisation de l’arginase et l’uréase pour améliorer les caractéristiques analytiques de biocapteur conductimétriques pour la détermination de la L-arginineCurrentwork presents a serie of conductometric (bio)sensors based on clinoptilolite, for ammonium, urea and L-arginine determination. Clinoptilolite, a nanoscale material possessing exceptional sorption and cation-exchange properties toward ammonium species, was initially used for the development of NH4+-selective conductometric microsensor. The clinoptilolite-based microsensor was selective toward ammonium in the presence of interferences that are commonly found along with ammonium in natural waters. Hereafter, an application of this nanomaterial in biosensors is favorable for operation in multicomponent buffer solutions. Among the several variants of the urea biosensors based on zeolite, considerably better characteristics were obtained for the biosensor comprising a clinoptilolite adlayer and an upper layer of immobilized urease and zeolite. In the work, for first time was developed a highly sensitive conductometric biosensor for L-arginine determination based on arginase and urease co-immobilized in a single membrane. The results of a quantitative determination of L-arginine in a drinkable solution “Arginine Veyron”, obtained by the biosensor, were in high correlation with the data provided by the producer. The L-arginine conductometric biosensor was optimized for the serum analysis. Clinoptilolite was also applied as a modifier in co-immobilization of arginase and urease for the improvement of analytical characteristics of the conductometric biosensor for L-arginine determinatio

Digital intelligence of a modern economist: an exploratory case study

In the current context of digitalization of various spheres of life, an important characteristic of participants in a digital society is the level of their digital intelligence. The level at which future economists develop their digital intelligence skills during university depends on their successful employment and career development. The presented article analyses the concept of digital intelligence of an economist on the basis of the Digital Quotient framework developed by the Digital Intelligence Institute, characterizing the levels of “Digital Citizen”, “Digital Creator”, “Digital Entrepreneur” for such components of digital intelligence as: Digital Changemaker Identity, Digital Use, Safety Digital, Digital Security, Digital Emotional Intelligence, Digital Communication, Digital Literacy, Digital Rights. For the first time, the contents of an academic discipline of a university training programme for future economists have been proposed, in the course of which digital intelligence skills can be developed. The authors demonstrate the stages of formation, indicators for different levels of formation, content and examples of educational representation of material. They offer the stages of Digital intelligence development in the framework of studying the course modules, the implementation of project work and the solution of the real case studies during academic training. The results of the pilot study for achieving all three levels of digital intelligence. A statistical analysis of the results of the experiment was carried out and their relevance proved

Ultra-sensitive conductometric detection of pesticides based on inhibition of esterase activity in Arthrospira platensis.

International audienceEnzymatic conductometric biosensor, using immobilized Arthrospira platensis cells on gold interdigitated electrodes, for the detection of pesticides in water, was elaborated. Cholinesterase activity (AChE) was inhibited by pesticides and a variation of the local conductivity was measured after addition of the substrate acetylthiocholine chloride (AChCl). The Michaelis-Menten constant (Km) was evaluated to be 1.8 mM through a calibration curve of AChCl. Inhibition of AChE was observed with paraoxon-methyl, parathion-methyl, triazine and diuron with a detection limit of 10(-18) M, 10(-20) M, 10(-20) M and 10(-12) M, respectively and the half maximal inhibitory concentration (IC50) was determined at 10(-16) M, 10(-20) M, 10(-18) M and 10(-06) M, respectively. An important decrease of response time τ90% was recorded for AChE response towards AChCl after 30 min cell exposure to pesticides. Scanning electron microscopy images revealed a degradation of the cell surface in presence of pesticides at 10(-06) M

Etude d'un biocapteur basé sur la mesure d'activité enzymatique de cellules de la Spiruline pour la détection des métaux lourds

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Biocapteur bimézymétrique conductimétrique pour la détection d'ions des métaux lourds et des pesticides dans des les eaux, basés sur l'inhibition enzymatique d'Arthrospira platensis

International audienceAn original bi-enzymatic biosensor was designed by immobilizing Arthrospira platensis cells, called Spirulina, on gold interdigitated transducers. Phosphatase and esterase activities were inhibited, respectively, by heavy metals and by pesticides. Inhibition activities were observed with different mixtures of pesticides + heavy metals. The quantification limits for Cd2+ and Hg2+ are 10−20 M in mixture and in pure solution. The quantification limits of parathion-methyl, paraoxon-methyl and triazine are respectively 10−20 M, 10−18 M and 10−20 M in mixture and pure solutions. These results show that there is no synergistic effect between the two families of pollutants. Qualitative contamination of effluent samples and their purification after passing through a municipal wastewater treatment plant were observed by our bi-enzymatic biosensor and confirmed by classical analytical techniques for heavy metal ions

NANOSIZED ZEOLITES AS A PERSPECTIVE MATERIAL FOR DEVELOPMENT OF ELECTROCHEMICAL ENZYME BIOSENSORS

In this work, the method of enzyme adsorption on different zeolites and mesoporous silica spheres (MSS) was investigated for the creation of conductometric biosensors. The conductometric transducers consisted of gold interdigitated electrodes were placed on the ceramic support. The transducers were modified with zeolites and MSS, and then the enzymes were adsorbed on the transducer surface. Different methods of zeolite attachment to the transducer surface were used; drop coating with heating to 200°C turned out to be the best one. Nanozeolites beta and L, zeolite L, MSS, and silicalite-1 (80 to 450 nm) were tested as the adsorbents for enzyme urease. The biosensors with all tested particles except zeolite L had good analytical characteristics. Silicalite-1 (450 nm) was also used for adsorption of glucose oxidase, acetylcholinesterase, and butyrylcholinesterase. The glucose and acetylcholine biosensors were successfully created, whereas butyrylcholinesterase was not adsorbed on silicalite-1. The enzyme adsorption on zeolites and MSS is simple, quick, well reproducible, does not require use of toxic compounds, and therefore can be recommended for the development of biosensors when these advantages are especially important