Magnetic Separation and Centri-Chronoamperometric Detection of Foodborne Bacteria Using Antibiotic-Coated Metallic Nanoparticles.

Quality and food safety represent a major stake and growing societal challenge in the world. Bacterial contamination of food and water resources is an element that pushes scientists to develop new means for the rapid and efficient detection and identification of these pathogens. Conventional detection tools are often bulky, laborious, expensive to buy, and, above all, require an analysis time of a few hours to several days. The interest in developing new, simple, rapid, and nonlaborious bacteriological diagnostic methods is therefore increasingly important for scientists, industry, and regulatory bodies. In this study, antibiotic-functionalized metallic nanoparticles were used to isolate and identify the foodborne bacterial strains Bacillus cereus and Shigella flexneri. With this aim, a new diagnostic tool for the rapid detection of foodborne pathogenic bacteria, gold nanoparticle-based centri-chronoamperometry, has been developed. Vancomycin was first stabilized at the surface of gold nanoparticles and then incubated with the bacteria B. cereus or S. flexneri to form the AuNP@vancomycin/bacteria complex. This complex was separated by centrifugation, then treated with hydrochloric acid and placed at the surface of a carbon microelectrode. The gold nanoparticles of the formed complex catalyzed the hydrogen reduction reaction, and the generated current was used as an analytical signal. Our results show the possibility of the simple and rapid detection of the S. flexneri and B. cereus strains at very low numbers of 3 cells/mL and 12 cells/mL, respectively. On the other hand, vancomycin-capped magnetic beads were easily synthesized and then used to separate the bacteria from the culture medium. The results show that vancomycin at the surface of these metallic nanoparticles is able to interact with the bacteria membrane and then used to separate the bacteria and to purify an inoculated medium.

Distribution of seroprevalence and risk factors for bovine tuberculosis in east Algeria.

Despite the difficulties and the absence of credible scientific information concerning bovine tuberculosis in Algeria, our cross-sectional and inferential study, which is estimated to be a first in Algeria, affected three major semi-intensive regions in East of Algeria, by analyzing 21 holdings which grouped 516 cattle in an intensive and semi-intensive breeding character over a period of 12 months, in order to estimate the seroprevalence and the risk factors those influence the emergence of the disease in these regions. A serological test (ELISA) was carried out on all collected sera, after a stratified two-level sampling. A generalized linear mixed model was used to identify risk factors associated with animal-level positivity. A multivariate descriptive analysis (MCA) was used to identify farm clusters associated with bTB seroprevalence. The results obtained allow us to classify Algeria on the epidemiological level in the field of bovine tuberculosis, in an intermediate situation with a seroprevalence rate of 3.49 % (95 % CI : 1,91, 507); between industrialized countries where the seroprevalence is mostly very low below 0,1% and developing countries with very high seroprevalence such as African-Asian countries. This intermediate epidemiological position is influenced by certain risk factors that are integrated into the three mechanisms commonly known by the scientific community: "contamination by the introduction of an animal"; "neighborhood contamination"; "recurrence". But what characterizes this study is the obtaining of a "Animals purchased from a country listed as not OTF" factor that has returned as a highly protective factor and contributed to the decrease in this seroprevalence, and put Algeria in an intermediate epidemiological situation according to our study, and this is due to a purchase channeled by the state which is exclusive of the countries certified OTF by the OIE.

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 × 10-2 to 2 × 105 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.

Electrochemical detection of influenza virus H9N2 based on both immunomagnetic extraction and gold catalysis using an immobilization-free screen printed carbon microelectrode.

Influenza is a viral infectious disease considered as a source of many health problems and enormous socioeconomic disruptions. Conventional methods are inadequate for in-field detection of the virus and generally suffer from being laborious and time-consuming. Thus, studies aiming to develop effective alternatives to conventional methods are urgently needed. In this work, we developed an approach for the isolation and detection of influenza A virus subtype H9N2. For this aim, two specific influenza receptors were used. The first, anti-matrix protein 2 (M2) antibody, was attached to iron magnetic nanoparticles (MNPs) and used for the isolation of the virus from allantoic fluid. The second biomolecule, Fetuin A, was attached to an electrochemical detectable label, gold nanoparticles (AuNPs), and used to detect the virus tacking advantage from fetuin-hemagglutinin interaction. The MNP-Influenza virus-AuNP formed complex was isolated and treated by an acid solution then the collected gold nanoparticles were deposited onto a screen printed carbon electrode. AuNPs catalyzes the hydrogen ions reduction in acidic medium while applying an appropriate potential, and the generated current signal was proportional to the virus titer. This approach allows the rapid detection of influenza virus A/H9N2 at a less than 16 HAU titer.

Towards the electrochemical diagnostic of influenza virus: development of a graphene-Au hybrid nanocomposite modified influenza virus biosensor based on neuraminidase activity.

An 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.