Defecation Induced by Stimulation of Sacral S2 Spinal Root in Cats

The aim of this study was to determine if stimulation of sacral spinal nerve roots can induce defecation in cats. In anesthetized cats, bipolar hook electrodes were placed on the S1-S3 dorsal and/or ventral roots. Stimulus pulses (1-50 Hz, 0.2 ms) were applied to an individual S1-S3 root to induce proximal/distal colon contractions and defecation. Balloon catheters were inserted into the proximal and distal colon to measure contraction pressure. Glass marbles were inserted into the rectum to demonstrate defecation by videotaping the elimination of marbles. Stimulation of the S2 ventral root at 7 Hz induced significantly (p<0.05) larger contractions (32±9 cmH2O) in both proximal and distal colon than stimulation of the S1 or S3 ventral root. Intermittent (5 times) stimulation (1 minute on and 1 minute off) of both dorsal and ventral S2 roots at 7 Hz produced reproducible colon contractions without fatigue, while continuous stimulation of 5-minute duration caused significant fatigue in colon contractions. Stimulation (7 Hz) of both dorsal and ventral S2 roots together successfully induced defecation that eliminated 1-2 marbles from the rectum. This study indicates the possibility to develop a novel neuromodulation device to restore defecation function after spinal cord injury using a minimally invasive surgical approach to insert a lead electrode via the sacral foramen to stimulate a sacral spinal root.

A Pencil-Lead Immunosensor for the Rapid Electrochemical Measurement of Anti-Diphtheria Toxin Antibodies

Diphtheria is a vaccine-preventable disease, yet immunization can wane over time to non-protective levels. We have developed a low-cost, miniaturized electroanalytical biosensor to quantify anti-diphtheria toxin (DTx) immunoglobulin G (anti-DTx IgG) antibody to minimize the risk for localized outbreaks. Two epitopes specific to DTx and recognized by antibodies generated post-vaccination were selected to create a bi-epitope peptide, biEP, by synthesizing the epitopes in tandem. The biEP peptide was conjugated to the surface of a pencil-lead electrode (PLE) integrated into a portable electrode holder. Captured anti-DTx IgG was measured by square wave voltammetry from the generation of hydroquinone (HQ) from the resulting immunocomplex. The performance of the biEP reagent presented high selectivity and specificity for DTx. Under the optimized working conditions, a logarithmic calibration curve showed good linearity over the concentration range of 10−5–10−1 IU mL−1 and achieved a limit of detection of 5 × 10−6 IU mL−1. The final device proved suitable for interrogating the immunity level against DTx in actual serum samples. Results showed good agreement with those obtained from a commercial enzyme-linked immunosorbent assay. In addition, the flexibility for conjugating other capture molecules to PLEs suggests that this technology could be easily adapted to the diagnoses of other pathogens.

Fabrication of an Extremely Cheap Poly(3,4-ethylenedioxythiophene) Modified Pencil Lead Electrode for Effective Hydroquinone Sensing

Hydroquinone (HQ) is one of the major deleterious metabolites of benzene in the human body, which has been implicated to cause various human diseases. In order to fabricate a feasible sensor for the accurate detection of HQ, we attempted to electrochemically modify a piece of common 2B pencil lead (PL) with the conductive poly(3,4-ethylenedioxythiophene) or PEDOT film to construct a PEDOT/PL electrode. We then examined the performance of PEDOT/PL in the detection of hydroquinone with different voltammetry methods. Our results have demonstrated that PEDOT film was able to dramatically enhance the electrochemical response of pencil lead electrode to hydroquinone and exhibited a good linear correlation between anodic peak current and the concentration of hydroquinone by either cyclic voltammetry or linear sweep voltammetry. The influences of PEDOT film thickness, sample pH, voltammetry scan rate, and possible chemical interferences on the measurement of hydroquinone have been discussed. The PEDOT film was further characterized by SEM with EDS and FTIR spectrum, as well as for stability with multiple measurements. Our results have demonstrated that the PEDOT modified PL electrode could be an attractive option to easily fabricate an economical sensor and provide an accurate and stable approach to monitoring various chemicals and biomolecules.

Paracetamol Sensing with a Pencil Lead Electrode Modified with Carbon Nanotubes and Polyvinylpyrrolidone

The determination of paracetamol is a common need in pharmaceutical and environmental samples for which a low-cost, rapid, and accurate sensor would be highly desirable. We develop a novel pencil graphite lead electrode (PGE) modified with single-wall carbon nanotubes (SWCNTs) and polyvinylpyrrolidone (PVP) polymer (PVP/SWCNT/PGE) for the voltammetric quantification of paracetamol. The sensor shows remarkable analytical performance in the determination of paracetamol at neutral pH, with a limit of detection of 0.38 μM and a linear response from 1 to 500 μM using square-wave voltammetry (SWV), which are well suited to the analysis of pharmaceutical preparations. The introduction of the polymer PVP can cause dramatic changes in the sensing performance of the electrode, depending on its specific architecture. These effects were investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The results indicate that the co-localization and dispersion of PVP throughout the carbon nanotubes on the electrode are key to its superior electrochemical performance, facilitating the electrical contact between the nanotubes and with the electrode surface. The application of this sensor to commercial syrup and tablet preparations is demonstrated with excellent results.

Discharge of hydronium ions on metal cathodes in the presence of pyridine

In this work, studies have been carried out on the electrochemical reduction of hydrogen (hydronium ion) from acidic aqueous solutions in the presence of an organic substance – pyridine. Electrolysis was carried out in an electrolyte with a sulfuric acid content (0.18; 0.36 M) with a pyridine additions of 8.4·10-3 M. Potentiostatic studies were carried out on a Potentiostat P-30Jcom Elins potentiostat using a three-electrode cell. Working electrodes (cathodes) were made of M1 copper with an area (S) of 0.09 cm2; aluminum (AD1) S – 0.125 cm2, zinc (Ts0A) S – 0.35 cm2, lead (Cl) S – 0.20 cm2, auxiliary (anode) – from a platinum plate with an area of 0.20 cm2, reference electrode – silver chloride (AgCl/Ag). In potentiometric measurements, the results are presented according to the average data obtained for 30 s of electrolysis in the potential range (-950 ÷ -1100 mV for AgCl/Ag), and in studies in the galvanostatic mode at current densities from 0 to 110 mV/cm2, the results are presented as average data, obtained in the initial 5 s of the process. The paper presents comparative data on the electrokinetic parameters studied under the same conditions of hydrogen discharge reactions at different cathodes in electrolytes with a sulfuric acid content of 0.36 M. It is shown that the highest discharge current density of the hydronium ion (Н3О+) is achieved at the copper electrode, and the lowest at the lead electrode. With the addition of 8.4∙10-3 M pyridine to the electrolyte, the reduction of hydrogen cations is somewhat reduced on the electrodes used, except for lead. The transfer coefficients of the hydrogen discharge at all electrodes are low, and with the addition of pyridine they decrease even more. The low transfer coefficients indicate that the process of the hydronium ion discharge proceeds in a non-activation mode. The lowest exchange current is recorded at the copper and lead electrode. At the zinc electrode, the exchange of current is one to two orders of magnitude higher than at the other electrodes, so it can be noted that at this electrode the system under consideration is closer to the equilibrium of state. The order of the reaction of the course of electrolysis by the hydronium cation on the copper, aluminum and zinc electrodes is close to unity. The addition of pyridine leads to a slight decrease in the order of the reaction. This is due to the fact that pyridine molecules in acidic solutions exist in the form of pyridinium ion, which is reduced at the cathode. In this case, a significant amount of hydrogen is absorbed, which should explain the decrease in the order of the reaction with respect to the hydronium ion in the presence of pyridine additives. The obtained low values of the transfer coefficients indicate that, during the discharge of hydronium ions, the process is limited to a greater extent by the concentration polarization. The diffusion nature of the reduction of hydronium ions in electrolytes with a sulfuric acid concentration of 0.18 and 0.36 M is also evidenced by data taken in a dynamic mode.

Synthesis of Valeric Acid by Selective Electrocatalytic Hydrogenation of Biomass-Derived Levulinic Acid

The electrocatalytic hydrogenation (ECH) of biomass-derived levulinic acid (LA) is a promising strategy to synthetize fine chemicals under ambient conditions by replacing the thermocatalytic hydrogenation at high temperature and high pressure. Herein, various metallic electrodes were investigated in the ECH of LA in a H-type divided cell. The effects of potential, electrolyte concentration, reactant concentration, and temperature on catalytic performance and Faradaic efficiency were systematically explored. The high conversion of LA (93%) and excellent “apparent” selectivity to valeric acid (VA) (94%) with a Faradaic efficiency of 46% can be achieved over a metallic lead electrode in 0.5 M H2SO4 electrolyte containing 0.2 M LA at an applied voltage of −1.8 V (vs. Ag/AgCl) for 4 h. The combination of adsorbed LA and adsorbed hydrogen (Hads) on the surface of the metallic lead electrode is key to the formation of VA. Interestingly, the reaction performance did not change significantly after eight cycles, while the surface of the metallic lead cathode became rough, which may expose more active sites for the ECH of LA to VA. However, there was some degree of corrosion for the metallic lead cathode in this strong acid environment. Therefore, it is necessary to improve the leaching-resistance of the cathode for the ECH of LA in future research.