Electrochemical sensor for catechol and dopamine based on a catalytic molecularly imprinted polymer-conducting polymer hybrid recognition element

One of the difficulties with using molecularly imprinted polymers (MIPs) and other electrically insulating materials as the recognition element in electrochemical sensors is the lack of a direct path for the conduction of electrons from the active sites to the electrode. We have sought to address this problem through the preparation and characterization of novel hybrid materials combining a catalytic MIP, capable of oxidizing the template, catechol, with an electrically conducting polymer. In this way a network of "molecular wires" assists in the conduction of electrons from the active sites within the MIP to the electrode surface. This was made possible by the design of a new monomer that combines orthogonal polymerizable functionality; comprising an aniline group and a methacrylamide. Conducting films were prepared on the surface of electrodes (Au on glass) by electropolymerization of the aniline moiety. A layer of MIP was photochemically grafted over the polyaniline, via N,N'-diethyldithiocarbamic acid benzyl ester (iniferter) activation of the methacrylamide groups. Detection of catechol by the hybrid-MIP sensor was found to be specific, and catechol oxidation was detected by cyclic voltammetry at the optimized operating conditions: potential range -0.6 V to +0.8 V (vs Ag/AgCl), scan rate 50 mV/s, PBS pH 7.4. The calibration curve for catechol was found to be linear to 144 µM, with a limit of detection of 228 nM. Catechol and dopamine were detected by the sensor, whereas analogues and potentially interfering compounds, including phenol, resorcinol, hydroquinone, serotonin, and ascorbic acid, had minimal effect (=3%) on the detection of either analyte. Nonimprinted hybrid electrodes and bare gold electrodes failed to give any response to catechol at concentrations below 0.5 mM. Finally, the catalytic properties of the sensor were characterized by chronoamperometry and were found to be consistent with Michaelis-Menten kinetics. © 2009 American Chemical Society.

The use of carbon and gold electrodes in anodic stripping voltammetric heavy metal sensors.

The use of anodic stripping voltammetry (ASV)has been proven in the past to be a precise and sensitive analytical method with an excellent limit of detection. Electrochemical sensors could help to avoid expensive and time consuming procedures as sample taking and storage and provide a both sensitive and reliable method for the direct monitoring of heavy metals in the aquatic environment. Solid electrodes which have been used in this work, were produced using previously developed methods. Commercially available and newly designed, screen printed carbon and gold plated working electrodes (WE) were compared. Good results were achieved with the screen printed and plated electrodes under conditions optimized for each electrode material. The electrode stability, reproducibility of single measurements and the limit of detection obtained for Pb were satisfactory (3*10-6mol/l on screen printed carbon WEs after 60 s of deposition and 6*10-6 mol/l on gold plated WEs after 5 min of deposition). Complete 3-electrode-sets (counter, reference and working electrode) were screen printed on different substrates (glass, polycarbonate and alumina). Also here, both carbon and gold were used as WE. Using 3-electrode-sets with a gold plated WE on glass was a limit of detection of 7*10-7 mol/l was achieved after only 60 s of deposition.

Evaluation of a simple disposable microband electrode device for amperometric gas sensing

We report a simple and facile methodology for constructing Pt (6.3 mm x 50 mu m) and Cu (6.3 mm x 30 mu m) annular microband electrodes for use in room temperature ionic liquids (RTILs) and propose their use for amperometric gas sensing. The suitability of microband electrodes for use in electrochemical analysis was examined in experiments on two systems. The first system studied to validate the electrochemical responses of the annular microband electrode was decamethylferrocene (DmFc), as a stable internal reference probe commonly used in ionic liquids, in [Pmim][NTf2], where the diffusion coefficients of DmFc and DmFc(+) and the standard electron rate constant for the DmFc/DmFc(+) couple were determined through fitting chronoamperometric and cyclic voltammetric responses with relevant simulations. These values are independently compared with those collected from a commercially available Pt microdisc electrode with excellent agreement. The second system focuses on O-2 reduction in [Pmim][NTf2], which is used as a model for gas sensing. The diffusion coefficients of O-2 and O-2(-) and the electron transfer rate constant were again obtained using chronoamperometry and cyclic voltammetry, along with simulations. Results determined from the microbands are again consistent to those evaluated from the Pt microdisc electrode when compared these results from home-made microband and commercially available microdisc electrodes. These observations indicate that the fabricated annular microband electrodes are suitable for quantitative measurements. Further the successful use of the Cu electrodes in the O-2 system suggests a cheap disposable sensor for gas detection. (C) 2013 Elsevier B.V. All rights reserved.

AgriSense: Multichannel disposable sensors for animal health disease diagnostics

Rapid and sensitive detection of viral infections associated with Bovine Respiratory Disease (BRD) in live animals is recognized as key to minimizing the impact of this disease. ELISA-based testing is limited as it typically relies on the detection of a single viral antibody subtype within an individual test sample and testing is relatively slow and expensive. We have recently initiated a new project entitled AgriSense to develop a novel low-cost and label-free, integrated bimodal electronic biosensor system for BRD. The biosensor system will consist of an integrated multichannel thin-film-transistor biosensor and an electrochemical impedance spectroscopy biosensor, interfaced with PDMS-based microfluidic sample delivery channels. By using both sensors in tandem, nonspecific binding biomolecules must have the same mass to charge ratio as the target analyte to elicit equivalent responses from both sensors. The system will target simultaneous multiplexed sensing of the four primary viral agents involved in the development of BRD: bovine herpesvirus-1 (BHV-1), bovine parainfluenza virus-3 (BPIV-3), bovine respiratory syncytial virus (BRSV), and bovine viral diarrhea (BVD). Optimized experimental conditions derived through model antigen-antibody studies will be applied to the detection of serological markers of BRD-related infections based on IgG interaction with a panel of sensor-immobilized viral proteins. This rapid, “cowside” multiplex sensor capability presents a major step forward in disease diagnosis, helping to ensure the integrity of the agri-food supply chain by reducing the risk of disease spread during animal movement and transport.