Voltammetric sensing of recombinant viral dengue virus 2 NS1 based on Au nanoparticle-decorated multiwalled carbon nanotube composites.

A homemade gold electrode is modified with a carbon nanotubes/gold nanoparticles nanocomposite to perform selective and sensitive electrochemical detection of dengue toxin. This nanostructured composite offers a large specific surface and a reactive interface allowing the immobilization of biological material. Dengue antibodies are immobilized on gold nanoparticles via covalent bonding for dengue toxin detection. The porous tridimensional network of carbon nanotubes and gold nanoparticles enhances the electrochemical signal and the overall performance of the sensor. After optimization, the system exhibits a high sensitivity of - 0.44 ± 0.01 µA per decade with wide linear range between 1 × 10-12 and 1 × 10-6 g/mL at a working potential of 0.22 V vs Ag/AgCl. The extremely low detection limit (3 × 10-13 g/mL) ranks this immunosensor as one of the most efficient reported in the literature for the detection of recombinant viral dengue virus 2 NS1. This biosensor also offers good selectivity, characterized by a low response to various non-specific targets and assays in human serum. The outstanding performances and the reproducibility of the system place the biosensor developed among the best candidates for future medical applications and for early diagnosis of dengue fever. Graphical abstract.

Functionalized tungsten disulfide nanotubes for dopamine and catechol detection in a tyrosinase-based amperometric biosensor design.

WS2 nanotubes functionalized with carboxylic acid functions (WS2-COOH) were used for improved immobilization of the enzyme tyrosinase in order to form an electrochemical biosensor towards catechol and dopamine. The nanotubes were deposited on glassy carbon electrodes using a dispersion-filtration-transfer procedure to assure the reproducibility of the deposits. After the electrochemical and morphological characterization of these WS2-COOH nanotube deposits, the formed biosensors showed very satisfying performance towards catechol detection with a linear range of 0.6-70 µmol L-1 and a sensitivity of 10.7 ± 0.2 mA L mol-1. The apparent Michaelis Menten constant of this system is slightly lower than the KM value of tyrosinase in solution, reflecting an excellent accessibility of the active site of the enzyme combined with a good mass transport of the target molecule through the deposit. For dopamine detection, we observed an accumulation of this substrate due to electrostatic interactions between the amine function of dopamine and the carboxylic acid groups of the nanotubes. This led to improved signal capture at low dopamine concentrations. With linear ranges of 0.5-10 µmol L-1 and 10-40 µmol L-1, and respective sensitivities of 6.2 ± 0.7 mA L mol-1 and 3.4 ± 0.4 mA L mol-1, the overall sensor performance is within the average of comparable results using carbon nanotubes. Nonetheless, the simplified handling of these nanotubes and their reduced environmental impact make these WS2-COOH nanotubes a promising nanomaterial for biosensing applications.

Controlled carbon nanotube layers for impedimetric immunosensors: High performance label free detection and quantification of anti-cholera toxin antibody.

An original impedimetric immunosensor was developed based on carbon nanotube (CNT) deposits with controlled thicknesses for enhanced electroactive surface areas leading to improved sensor performances. Cholera monitoring was chosen as the model immune system for this setup. These CNT deposits were characterized using confocal laser microscopy and electrochemical methods. To form the sensor device, the CNT deposits were functionalized via electrocoating of polypyrrole-nitrilotriacetic acid (poly(pyrrole-NTA)) followed by the formation of a Cu (II) complex with the NTA functions. The bioreceptor unit, cholera toxin B Subunit, modified with biotin, was then immobilized via coordination of the biotin groups with the NTA-Cu(II) complex. Each step of the formation of the immunosensor and the subsequent binding of the analyte antibody anti-cholera toxin were investigated with cyclic voltammetry and Electrochemical Impedance Spectroscopy. After optimization, the resulting impedimetric cholera sensor shows excellent reproducibility, increased sensitivities, a very satisfying detection limit of 10-13gmL-1 and an exceptional linear range for anti-cholera detection of 8 orders of magnitude (10-13-10-5gmL-1) and a sensitivity of 24.7 ± 0.4Ω per order of magnitude.