Nanoparticles modified screen printed electrode for electrochemical determination of COD

The Chemical Oxygen Demand (COD) is a parameter widely used to determine organic pollutants in water and is defined as the number of oxygen equivalents necessary to oxidize the organic compounds. The standard method for COD measurement (the dichromate titration) suffers from several inherent drawbacks such as the long time of the process and the consumption of toxic chemicals. Hence, interest is growing towards those methods employing electrochemical oxidation of organic compounds, as they allow to dispense with toxic reagents and above all to perform a continuous determination. In this work a new electrochemical method for COD measurement has been developed based on direct oxidation of organic molecules on suitably modified electrodic surfaces. In particular, we have developed various sensors based on modified working electrode surfaces obtained by electrodepositing copper and/or nickel oxide nanoparticles onto several commercial screen printed electrodes. Glucose was used as the standard compound for COD measurements: C6H12O6 + 6O2 → 6CO2 + 6H2O The metallic nanoparticles catalyze the oxidation of the glucose, as well as of different organic pollutants, and make the detection possible at relatively low potential, also in presence of chloride as interferent. The analytical parameters were optimized and the results obtained highlight how the electrodeposition of different metallic nanoparticles onto several screen printed electrode surfaces can influence the selectivity and sensitivity towards the COD detection in real matrices, via electrochemical method. The results were compared with those obtained by the standard method and showed a good agreement. These findings provide an interesting strategy to obtain a simple, cheap, portable and eventually continuous sensor for COD measurement

Inhibition-Based Electrochemical Biosensor for Atrazine Detection

This work presents an inhibition based biosensor for the fast, simple and inexpensive determination of atrazine. The method is based on the inhibition of the enzyme tyrosinase from mushrooms (Tyr), immobilized on screen printed electrodes (SPEs). To optimize the biosensor performances several carbon based SPEs (graphite (G), graphene (GP), and multiwalled carbon nanotubes (MWCNTs)) and immobilization techniques (physical and chemical) have been tested. Tyrosinase was immobilized on the electrode surface by either polyvinyl alcohol with stiril-pyridinium groups (PVA-SbQ) as cross-linking agent or Nafion membranes as physical entrapment or bovine serum albumin with glutaraldehyde as chemical immobilization. In the presence of catechol as substrate, atrazine can be determined thanks to its inhibition activity towards the enzyme which catalyzes the oxidation of catechol to o-quinone. Under optimum experimental conditions, the best performance in terms of catalytic efficiency has been demonstrated by MWCNTs screen printed electrode with PVA-SbQ as immobilization method. The developed inhibition biosensor displays a linearity range towards atrazine within 0.5-20 ppm, a LOD of 0.3 ppm and acceptable repeatability and stability. This analysis method was applied to spiked drinking water samples with recoveries close to 95% respect to measurements carried out in PBS buffer. The low cost of this device and its good analytical performances suggest its application for the screening and monitoring of atrazine in real matrices

AuNPs-functionalized PANABA-MWCNTs nanocomposite-based impedimetric immunosensor for 2,4-dichlorophenoxy acetic acid detection

In this work, we developed an impedimetric label-free immunosensor for the detection of 2,4-Dichlorophenoxy Acetic Acid (2,4-D) herbicide either in standard solution and spiked real samples. For this purpose, we prepared by electropolymerization a conductive polymer poly-(aniline-co-3-aminobenzoic acid) (PANABA) then we immobilized anti-2,4-D antibody onto a nanocomposite AuNPs-PANABA-MWCNTs employing the carboxylic moieties as anchor sites. The nanocomposite was synthesized by electrochemical polymerization of aniline and 3-aminobenzoic acid, in the presence of a dispersion of gold nanoparticles, onto a multi-walled carbon nanotubes-based screen printed electrode. Aniline-based copolymer, modified with the nanomaterials, allowed to enhance the electrode conductivity thus obtaining a more sensitive antigen detection. The impedimetric measurements were carried out by electrochemical impedance spectroscopy (EIS) in faradic condition by using Fe(CN)6(3-/4-) as redox probe

Synthesis and Enantiomeric Separation of a Novel Spiroketal Derivative:A Potent Human Telomerase Inhibitor with High in Vitro Anticancer Activity

The synthesis, the enantiomeric separation, and the characterization of new simple spiroketal derivatives have been performed. The synthesized compounds have shown a very high anticancer activity. Cell proliferation assay showed that they induce a remarkable inhibition of cell proliferation in all cell lines treated, depending on culture time and concentration. The compounds have also shown a potent nanomolar human telomerase inhibition activity and apoptosis induction. CD melting experiments demonstrate that spiroketal does not affect the G-quadruplex (G4) thermal stability. Docking studies showed that telomerase inhibition could be determined by a spiroketal interaction with the telomerase enzyme