Mise au point d’aptacapteurs pour la détection de mycotoxines

Le travail réalisé au cours de cette thèse a porté sur le développement de biocapteurs électrochimiques d’affinité, sensibles et sélectifs, pour la détection de l’ochratoxine A (OTA) et l’aflatoxine M1 (AFM1). Les biocapteurs développés reposent sur l’association de différents nanomatériaux pour une meilleure performance analytique. Pour construire notre transducteur, nous avons associé le polypyrrole à des dendrimères poly(amido-amine) PAMAM, ce qui a permis d’avoir de très bon rendements grâce au propriétés électriques du polypyrrole et à l’augmentation de la surface active due à la structure tridimensionnelle des dendrimères. L’utilisation d’aptamères spécifiques pour la détection des différentes mycotoxines a permis leur détection et quantification à des concentrations de l’ordre des nM, ainsi que l’élargissement des gammes dynamiques. Nous avons pu démontrer grâce à l’utilisation de dendrimères de différentes tailles que la sensibilité des biocapteurs ne provient pas uniquement de l’affinité qui existe entre les biorécepteurs et leurs molécules cibles, mais aussi des propriétés physico-chimiques du biocapteur.This aim of this work is to develop ultrasensitive electrochemical biosensors with high affinity toward ochratoxine (OTA) and aflatoxine M1 (AFM1). In order to obtain the best analytical performances, we associated nano-materials in the transducer construction: conducting polypyrrole polymer and poly(amido-amine) dendrimères. Thanks to this association, we benefited from the conducting material’s electrical properties, and the large active detection surface dendrimers. For the bimolecular sensing part, we used specific DNA aptamers which allowed us to quantify mycotoxines at nM concentrations. In addition, the different aptamer based biosensors present a very large dynamic ranges. We also demonstrated through the use of different sizes of dendrimers, that the sensitivity depend not only in the affinity between bioreceptors and their target molecules, but also in the physico-chemical properties of the biosensor

E-DNA Sensor of Mycobacterium tuberculosis Based on Electrochemical Assembly of Nanomaterials (MWCNTs/PPy/PAMAM).

International audienceTwo-step electrochemical patterning methods have been employed to elaborate composite nanomaterials formed with multiwalled carbon nanotubes (MWCNTs) coated with polypyrrole (PPy) and redox PAMAM dendrimers. The nanomaterial has been demonstrated as a molecular transducer for electrochemical DNA detection. The nanocomposite MWCNTs-PPy has been formed by wrapping the PPy film on MWCNTs during electrochemical polymerization of pyrrole on the gold electrode. The MWCNTs-PPy layer was modified with PAMAM dendrimers of fourth generation (PAMAM G4) with covalent bonding by electro-oxidation method. Ferrocenyl groups were then attached to the surface as a redox marker. The electrochemical properties of the nanomaterial (MWCNTs-PPy-PAMAM-Fc) were studied using both square wave voltammetry and cyclic voltammetry to demonstrate efficient electron transfer. The nanomaterial shows high performance in the electrochemical detection of DNA hybridization leading to a variation in the electrochemical signal of ferrocene with a detection limit of 0.3 fM. Furthermore, the biosensor demonstrates ability for sensing DNA of rpoB gene of Mycobacterium tuberculosis in real PCR samples. Developed biosensor was suitable for detection of sequences with a single nucleotide polymorphism (SNP) T (TCG/TTG), responsible for resistance of M. tuberculosis to rifampicin drug, and discriminating them from wild-type samples without such mutation. This shows potential of such systems for further application in pathogens diagnostic and therapeutic purpose

Direct detection of OTA by impedimetric aptasensor based on modified polypyrrole-dendrimers

International audienceOchratoxin A (OTA) is a carcinogenic mycotoxin that contaminates food such as cereals, wine and beer; therefore it represents a risk for human health. Consequently, the allowed concentration of OTA in food is regulated by governmental organizations and its detection is of major agronomical interest. In the current study we report the development of an electrochemical aptasensor able to directly detect trace OTA without any amplification procedure. This aptasensor was constructed by coating the surface of a gold electrode with a film layer of modified polypyrrole (PPy), which was thereafter covalently bound to polyamidoamine dendrimers of the fourth generation (PAMAM G4). Finally, DNA aptamers that specifically binds OTA were covalently bound to the PAMAM G4 providing the aptasensor, which was characterized by using both Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques. The study of OTA detection by the constructed electrochemical aptasensor was performed using Electrochemical Impedance Spectroscopy (EIS) and revealed that the presence of OTA led to the modification of the electrical properties of the PPy layer. These modifications could be assigned to conformational changes in the folding of the aptamers upon specific binding of OTA. The aptasensor had a dynamic range of up to 5 μg L−1 of OTA and a detection limit of 2 ng L−1 of OTA, which is below the OTA concentration allowed in food by the European regulations. The efficient detection of OTA by this electrochemical aptasensor provides an unforeseen platform that could be used for the detection of various small molecules through specific aptamer association

A regionally based precision medicine implementation initiative in North Africa:The PerMediNA consortium

International audiencePrecision Medicine is being increasingly used in the developed world to improve health care. While several Precision Medicine (PM) initiatives have been launched worldwide, their implementations have proven to be more challenging particularly in low- and middle-income countries. To address this issue, the “Personalized Medicine in North Africa” initiative (PerMediNA) was launched in three North African countries namely Tunisia, Algeria and Morocco. PerMediNA is coordinated by Institut Pasteur de Tunis together with the French Ministry for Europe and Foreign Affairs, with the support of Institut Pasteur in France. The project is carried out along with Institut Pasteur d’Algérie and Institut Pasteur du Maroc in collaboration with national and international leading institutions in the field of PM including Institut Gustave Roussy in Paris. PerMediNA aims to assess the readiness level of PM implementation in North Africa, to strengthen PM infrastructure, to provide workforce training, to generate genomic data on North African populations, to implement cost effective, affordable and sustainable genetic testing for cancer patients and to inform policy makers on how to translate research knowledge into health products and services. Gender equity and involvement of young scientists in this implementation process are other key goals of the PerMediNA project.In this paper, we are describing PerMediNA as the first PM implementation initiative in North Africa. Such initiatives contribute significantly in shortening existing health disparities and inequities between developed and developing countries and accelerate access to innovative treatments for global health