Towards the Electrochemical Diagnostic of Influenza Virus: Development of Graphene-Au Hybrid Nanocomposite Modified Influenza Virus Biosensor Based on Neuraminidase Activity

International audienceAn effective electrochemical influenza A biosensor based on a graphene-gold (Au) hybrid nanocomposite modified Au-screen printed electrode has been developed. The working principle of the developed biosensor relies on the measurement of neuraminidase (N) activity. After the optimization of experimental parameters like the effect of bovine serum albumin addition and immobilization times of fetuin A and PNA lectin, the analytical characteristics of the influenza A biosensor were investigated. As a result, a linear range between 10-8 U mL-1 and 10-1 U mL-1 was found with a relative standard deviation value of 3.23% (for 10-5 U mL-1 of N, n:3) and a limit of detection value of 10-8 U mL-1 N. The developed biosensor was applied for real influenza virus A (H9N2) detection and very successful results were obtained

Automated detection and tracking of phlebotominaes

International audienceThis paper presents a method for detecting and tracking phlebotominaes that are vectors for many important diseases. A method based on the Gaussian mixture model is used for Foreground/Background classification. Then, the mathematical morphology operations are used to refine theclassification results and eliminate areas that do not represent phlebotominaes. Thereafter, the Kalman filter is used for the prediction and stimation of their positions, thus the Hungarian algorithm is used for the assignment of the detected positions to tracks. The results can help us study the behavior of these insects, and to improve traps and solutions that limit their spread in case of infection. The proposed method is tested on a real phlebotominaes video sequences recorded at Pasteur institute of Tunisia, and the experimental results show the efficiency of the proposed algorithm to accurately detect the position and track phlebotominaes

Casein-Conjugated Gold Nanoparticles for Amperometric Detection of Leishmania infantum

Sensitive and reliable approaches targeting the detection of Leishmania are critical for effective early diagnosis and treatment of leishmaniasis. In this frame, this paper describes a rapid quantification assay to detect Leishmania parasites based on the combination of the electrocatalytic ability of gold nanoparticles (AuNPs) to act as a catalyst for the hydrogen formation reaction along with the specificity of the interaction between casein and the major surface protease of the Leishmania parasite, GP63. First, pure and casein-modified AuNPs were prepared and characterized by scanning electron microscopy and ultraviolet-visible spectroscopy. Then, casein-conjugated AuNPs were incubated with Leishsmania parasites in solution; the formed complex was collected by centrifugation, treated by acidic solution, and the pelleted AuNPs were placed on screen-printed carbon electrodes (SPCEs) and chronoamperometric measurements were carried out. Our results suggest that it is possible to detect Leishmania parasites, with a limit less than 1 parasite/mL. A linear response over a wide concentration interval, ranging from 2 x 10(-2) to 2 x 10(5) parasites/mL, was achieved. Additionally, a pretreatment of Leishmania parasites with Amphotericin B, diminished their interaction with casein. This findings and methodology are very useful for drug efficacy assessment

Synthesis and Characterization of Novel Sprayed Ag-Doped Quaternary Cu₂MgSnS₄ Thin Film for Antibacterial Application

In this work, the effects of silver doping with different Ag/(Ag + Cu) ratios (i.e., 2%, 5% and 10% at.% in the spray solution) on the structural, morphological, optical, electrical and antibacterial properties of Cu2MgSnS4 (CMTS) thin film grown by spray pyrolysis have been studied. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) results have shown that the kesterite phase of CMTS thin films has a maximum crystallite size of about 19.60 nm for 5% Ag/(Ag + Cu). Scanning electron microscopy (SEM) images have shown spherical grain shapes. The transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) microscopy observations confirmed the intrinsic reticular planes of CMTS thin film with (112) as a preferred orientation and interplanar spacing value of 3.1 Å. The optical properties showed high absorbance and an absorption coefficient of about 104 cm−1 in the visible region with an optical band gap energy of 1.51 eV. Impedance analysis spectroscopy demonstrated good electrical properties of the CMTS film obtained using 5% Ag/(Ag + Cu). The antibacterial activity of the undoped and Ag-doped particles of CMTS obtained using 5% Ag/(Ag + Cu) against different strains of pathogenic bacteria was tested using the agar well diffusion method. These results showed a significant antibacterial activity of the Ag-doped CMTS particle, which was much higher than the undoped CMTS particles. These experimental findings may open new practices for the Ag-doped CMTS compound, especially the one obtained using 5% Ag/(Ag + Cu), in antibacterial application

Immobilization of specific antibody on SAM functionalized gold electrode for rabies virus detection by electrochemical impedance spectroscopy

International audienceThe rabies constitutes one of the most dangerous viruses causing many death cases every year. Each year approximately 55,000 people die of rabies, with high percentage of children. High percentages (99%) of the registered cases were in Asia and Africa. In order to fight this dangerous disease, many techniques are usually used for diagnostic but are usually complex, heavy, expensive, difficult to implement, requiring high-qualified personnel, and this is a necessity of developing new detection process. In this work, we describe the development of an immunological sensor based on functionalized gold electrode allowing rabies antigen detection. The biosensor is based on the immobilization of specific rabies antibodies onto functionalized gold microelectrode. The affinity interaction of the immobilized antibody with the specific antigen can be measured with low limit detection and with a good reproducibility with impedance spectroscopy. The non-specific interaction has been tested using the Newcastle antigen. (c) 2007 Elsevier B.V. All rights reserved

Detection of ESAT-6 by a label free miniature immuno-electrochemical biosensor as a diagnostic tool for tuberculosis

International audienceTuberculosis is a worldwide disease considered as a major health problem with high morbidity and mortality rates. Poor detection of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis remains a major obstacle to the global control of this disease. Here we report the development of a new test based on the detection of the major virulent factor of Mtb, namely the early secreted antigenic target 6-kDa protein or ESAT-6. A label free electrochemical immunosensor using an anti-ESAT-6 monoclonal antibody as a bio-receptor is described herein. Anti-ESAT-6 antibodies were first covalently immobilized on the surface of a gold screen-printed electrode functionalized via a self-assembled thiol monolayer. Interaction between the bio-receptor and ESAT-6 antigen was evaluated by square wave voltammetry method using [Fe(CN)6](3-/4-) as redox probe. The detection limit of ESAT-6 antigen was 7ng/ml. The immunosensor has also been able to detect native ESAT-6 antigen secreted in cell culture filtrates of three pathogenic strains of Mtb (CDC1551, H37RV and H8N8). Overall, this work describes an immune-electrochemical biosensor, based on ESAT-6 antigen detection, as a useful diagnostic tool for tuberculosis

Ultrasensitive detection of hazardous reactive oxygen species using flexible organic transistors with polyphenol-embedded conjugated polymer sensing layers.

International audienceHere we report that superoxide, one of the hazardous reactive oxygen species (ROS), can be quickly detected by flexible organic field-effect transistors (OFETs) with the polyphenol-embedded conjugated polymer micro-channels. Rutin, one of the abundant polyphenols found in a variety of plants, was employed as a sensing molecule and embedded in the poly(3-hexylthiophene) (P3HT) matrix. The rutin-embedded P3HT layers showed randomly distributed micro-domains, which became bigger as the rutin content increased. The best transistor performance was achieved at the rutin content of 10 wt%, while the OFETs exhibited proper and controllable transistor performances even in the phosphate buffer solutions. The sensing test revealed that the present OFET sensors could stably detect superoxide using very small amount (\textless10 μl) of samples at extremely low concentrations (500 pM), while they exhibited outstanding stability and durability upon repeated detection and storage-reuse tests. Finally, the present flexible OFET sensors could deliver confident sensing results for the detection of superoxide generated from the mouse RAW264.7 macrophages

Chemical Composition and Anti-Leishmania Major Activity of Essential Oils from Artemesia spp. Grown in Central Tunisia

peer reviewedNatural products are a very important source of bio-molecules for drug to treat infectious diseases. New antileishmanial agents are timely needed, due to leishmania toxicity, drug-resistant strains and high costs treatments. In this study, we report the chemical characterization and antileishmanial activity of oil extracts from three medicinal plants belonging to genus Artemisia (Asteracea), that grow in central Tunisia. The chemical composition of volatile compounds had been elucidated by gas chromatography-mass spectroscopy analysis. Chemical analysis revealed that essential oils were composed of 34 compounds: α-thujone (29.3%), chamazulene (39.2%) and β-pinene (32%), were the main constituents for the essential oils of Artemesia herba alba, Artemesia absinthium and Artemesia campestris, respectively. The hydrodistilled essential oils from these three species of Artemisia showed significant anti-leishmanial activities against Leishmania major. Oils from A. herba alba, A. absinthium and A. campestris exhibited IC50 values of 1.20 ± 0.043 μg/mL, 1.49 ± 0.05 μg/mL and 2.20 ± 0.11 μg/mL respectively against promastigotes of Leishmania major. Among three oils tested, A. campestris exerted a remarkable antileishmanial activity and it has the lowest cytotoxicity effect compared to amphotericin B. Overall, it was proved that our investigated essential oils possess potential antileishmanial properties and could be used as a promising alternative treatment for leishmaniasis disease in the future

Blood Meal Analysis of Phlebotomine Sandflies (Diptera: Psychodidae: Phlebotominae) for Leishmania spp. Identification and Vertebrate Blood Origin, Central Tunisia, 2015-2016.

International audienceDuring the time periods of June 2015 and from July to August 2016, sandflies were collected among seven collection sites of the three leishmaniasis endemic villages of Sidi Bouzid, Tunisia. A total of 690 sandflies were captured and identified (380 males and 310 females). Four species belonging to genus Phlebotomus (Ph.) and two species belonging to genus Sergentomyia were identified. Leishmania DNA was detected in four out of 310 females (one Ph. sergenti and three Ph. papatasi). The overall sensitivity of the Prepronociceptin gene detection reached 76%. The concurrent presence of Ph. papatasi and Ph. sergenti vectors, the analysis of blood-meals, together with the detection of L. major in Ph. papatasi, confirms the ultimate conditions for the transmission of the disease in center Tunisia. These results expand the known epidemiological area of distrubtion of leishmaniasis and its vectors in this part of Tunisia, highlighting the need for ongoing entomological and parasitological surveillance