RESUMEN
In this study, the effect of amperometric glucose biosensor construction and using conditions on the current response was investigated in detail applying experimental design. Polyaniline (PANI) was synthesized on the carbon paste electrode (CPE) surface using the cyclic voltammetry technique in sodium oxalate (NaOx ) electrolyte medium, and an amperometric biosensor was constructed by immobilizing glucose oxidase (GOD). Biosensor preparation (aniline, GOD and NaOx concentrations, and scan rate) and operating conditions (pH and applied potential) were optimized by Box-Behnken and optimal designs, respectively, via State Ease Design Expert 7.0.1.1 software. ANOVA analyses showed that among the biosensor preparation parameters, the NaOx concentration has the highest effect on the current measured in the presence of glucose, whereas in the optimization of pH and potential parameters applied in current measurement studies, it has been revealed that pH has a very high effect on the measured current. Several compounds, such as MWCNT, two different ionic liquids and two different organic molecules were added to carbon paste, and, among them, 2-cyanoethylpyrrole (CPy) enhanced the efficacy highly, most probably due to its polymerization in the paste and increasing the electron transfer rate of the CPE. Sucrose- and lactose-sensitive biosensors were also constructed by co-immobilizing GOD with invertase (INV) or ß-galactosidase, respectively, onto modified CPE, and sensitivities to their substrates were shown by cyclic voltammetry and impedance analysis. CPy modification caused an increase in the current values, and also Imax /KM values increased approximately 11.8, 7.83, and 2.56 times for glucose-, sucrose-, and lactose-sensitive CPEs, respectively.
Asunto(s)
Técnicas Biosensibles , Carbono , Carbono/química , Lactosa , Electrodos , Técnicas Biosensibles/métodos , Compuestos de Anilina/química , Glucosa/química , Glucosa Oxidasa/química , SacarosaRESUMEN
GOD was immobilized onto polypyrrole (PPy) or poly(o-anisidine) (POA) coated Pt electrode to construct glucose sensitive biosensor. Because polymer film properties and enzyme activity affect the current response, PPy and POA synthesis conditions and also enzyme immobilization parameters were optimized in detail. The optimal monomer concentrations were determined as 25 and 50 mM for PPy and POA, respectively, whereas scan rate was 50 mV/s for both polymer films. In case of immobilization procedure, the optimal Chitosan (Chi), glucose oxidase (GOD) and glutaraldehyde (GAL) concentrations were determined as 0.5%, 2 mg/ml and 0.05% for PPy and 0.5%, 4 mg/ml and 0.075% for POA, respectively. Zinc oxide nanoparticles (ZnONP) were co-immobilized with GOD enzyme and it was revealed that ZnONP modification enhanced the efficiencies of both electrodes in terms of current responses and stabilities. Nyquist diagrams showed that enzyme electrodes were sensitive to glucose molecule and ZnONP modification improved the sensor efficiency.
RESUMEN
In this study, zinc-nickel (ZnNi) particles were electrochemically deposited on carbon steel (CS) electrode applying constant current of 1 mA with chronopotentiometry technique. Poly(N-methylpyrrole) (PNMP) film on CS/ZnNi electrode was synthesized with cyclic voltammetry technique from 0.10 M N-methylpyrrole containing 0.20 M sodium oxalate solution. The corrosion performances of coated and uncoated electrodes in 3.5% NaCl solution were evaluated with the help of AC impedance spectroscopy (EIS) and anodic polarisation curves. Scanning electron microscopy (SEM) and linear sweep voltammetry (LSV) were used to characterization of coatings. It was shown that the ZnNi particles exhibited important barrier effect on CS substrate. The highest 298350 ohm value of polarization resistance showed that PNMP film on the CS/ZnNi electrode exhibited an effective barrier property and electrocatalytic behaviour protection of substrate for longer exposure time.
RESUMEN
Zinc-iron (ZnFe) and zinc-iron-cobalt (ZnFeCo) platings were achieved on carbon steel applying 3 mA current values. Then, oxalate (OX) and tartrate (Tart) passive layers obtained in sodium oxalate and sodium tartrate medium were formed on carbon steel, ZnFe and ZnFeCo plated carbon steel. SEM images showed that the passive layers on CS, CS/ZnFe and CS/ZnFeCo electrodes exhibited different crystal structures. Corrosion tests revealed that the ZnFeCo particles provided a significant barrier efficiency on CS layer when compared with ZnFe alloy plating. Furthermore, OX layers on ZnFe and ZnFeCo plated carbon steel electrodes exhibited better physical barrier behavior on than those of Tart layers in longer periods.
RESUMEN
We aimed to assess the efficacy of multimodal epidural analgesia in decreasing postoperative pain after microdiscectomy. Fourty patients, ASA physical status I or II, undergoing microsurgical lumbar discectomy were enrolled in this prospective, randomised, controlled, double-blinded study. 10 ml study solution consisting of 2 mg of morphine, 15 mg of bupivacaine, 80 mg of methylprednisolone, and 0.05 mg of adrenaline was prepared for epidural administration. At the end of the procedure but prior to wound closure, the surgeon inserted an 18-gauge epidural catheter into the epidural space. After closure of incision, patients were assigned to receive either study solution (Group E) or saline (Group C). The epidural catheter was then removed. Patient controlled analgesia with morphine was used for postoperative analgesia. Visual Anologue Scale (VAS) pain scores and morphine consumptions were lower in Group E. Time to first ambulation was shorter in Group E. Patients in Group E were more satisfied with their analgesic regimen. Single dose multimodal epidural analgesia administered after wound closure provided better postoperative analgesia after lumbar microdiscectomy.