RESUMEN

Pepsin as an aspartic acid protease member and one of the three foremost proteolytic enzymes in the digestive system is essential to be detected. An electrochemically polymerized tyrosine film on carbon paste electrode (pTyr/CPE) has been synthesized by electro-polymerization donating an affordable electrochemical sensor to sense salivary pepsin as a diagnostic technique for gastroesophageal reflux disease (GRD) due to saliva collection is non-invasive and relatively comfortable. The pTyr/CPE was applied for Voltammetric sensing of pepsin and its quantification in phosphate buffer solution of pH 2.0 (PBS). Scanning electron microscopy (SEM) was conducted to learn the surface morphology. Cyclic voltammetry (CV), differential pulse voltammetry (DPVs), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were developed to realize the electrocatalytic activity of the sensor. The pTyr/CPE proceeded as a sensitive detector to pepsin with two linear ranges from 1 to 20 & 20 to 100 ng/mL donating two limits of detection as 0.5 & 0.09 ng/mL, respectively, and high selectivity toward pepsin, as well as stability and fast response of 1.5 s. Consequently, it is guessed that the pTyr/CPE sensor could be supportive for the initial diagnosis of GRD through the detection of pepsin in saliva. Finally, we quantified the pepsin levels in saliva samples of LPR patients (n = 2), showing that the results were agreeable with those from the electrochemical sensor.

Asunto(s)

RESUMEN

The mechanism of interaction between magnesite mineral and phosphoric acid (0.001-0.5 M) in addition to the determination of the protective properties for Ti alloy (working electrode) in phosphoric acid both with and without an inhibitor have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Results of electrochemical tests show that the corrosion resistance of titanium alloy in phosphoric acid solution only increased and hydrogen production decreased by either decreasing acid concentration or increasing immersion time associated with the thickening of the oxide film formed on the alloy surface. On adding magnesite, the corrosion resistance of Ti alloy is enhanced by increasing the phosphoric acid concentration (0.001-0.5 M) due to the formation of sparingly soluble magnesium phosphate film on the alloy surface that inhibits the effect of increasing hydrogen evolution reaction due to the pH value decreases. The increasing adsorption behavior of the magnesite inhibitor and decreasing its diffusion were deduced from EIS measurements. Thus, the addition of 3% magnesite minimizes the corrosion by forming a new protective film (Mg3(PO4)2), which differs from the traditional passive film and prevents the effect of the increase of hydrogen evolution. The surface morphology and chemical composition of the tested alloy were determined using scanning electron microscopy (SEM), Fourier transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), X-ray Fluorescence (XRF) and In situ Raman spectroscopy.

RESUMEN

A profoundly touchy voltammetric sensor for detection of nicotine (NIC) in urine and tobacco specimens has been developed in light of the boosted electrochemical response of NIC at gold and chitosan nanocomposite modified carbon paste electrode (ACMCPE). Material characterization techniques Scanning Electron Microscope and Energy Dispersive X-ray (SEM & EDX) were utilized to describe the ACMCPE surface material. The impedance spectroscopy technique (EIS), cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV) were employed to explore the electrochemical sensing of NIC at ACMCPE. The created sensor exhibits an exceptional electrochemical sensitivity to NIC in a universal Britton-Robinson (B-R) buffer solution with a pH range of 2.0 to 8.0. The sensor shows a linear response over NIC concentration ranges of 4.0-320.0 µM, with the detection limit (LOD) of 7.6 µM. The prepared sensor has been shown to be exceptionally viable in detecting NIC with amazing selectivity and reproducibility. We suggest it as a trustworthy and useful electrochemical sensor for NIC location.

Asunto(s)

RESUMEN

Corrosion inhibition of molybdenum electrode in H3PO4 acid medium of different concentrations (3.0 to 13 M) has been investigated utilizing different electrochemical techniques. It was observed that the most corrosive concentration is 3.0 M orthophosphoric acid concentration. The effect of adding Cl- to 3.0 M orthophosphoric acid in the concentration range of 0.1 to 1.0 M was also studied. This study showed that the most corrosive medium is 3.0 M containing 1.0 M chloride ion with the greatest rate of hydrogen production. In 3.0 M H3PO4 acid with 1.0 M of NaCl, the tested electrode's corrosion and hydrogen production may be successfully suppressed by adding Streptomycin of 10 mM concentration leading to high inhibition efficiency. The outcomes of the studies were confirmed by scanning electron microscopic examination. Additionally, a computational chemistry approach was used to investigate how streptomycin adsorbs and inhibits corrosion at the interface of metal surfaces, and the outcomes of the computational studies are in excellent accord with the experimental findings.

Asunto(s)

RESUMEN

A new electrochemical sensor for the detection of levofloxacin (LV) was efficiently realized. The aim was to develop a new, cheap, and simple sensor for the detection of LV, which is used in various infections due to its pharmacological importance. It consists of carbon paste (CP) enhanced with nano-sized fumed silica (NFS). NFS has a very low bulk density and a large surface area. The carbon paste-enhanced NFS electrode (NFS/CPE) showed great electrocatalytic activity in the oxidation of 1.0 mM LV in Britton-Robinson buffer (BR) at pH values ranging from 3.0 to 8.0. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used; the peak current value (Ip) of the NFS/CPE sensor was 2.7 times that of the bare electrode, ensuring its high electrocatalytic activity. Electrochemical impedance spectroscopy (EIS) was performed at a peak potential (Ep) of +1066 mV, yielding a resistance of 10 kΩ for the designed NFS/CPE sensor compared to 2461 kΩ for the bare electrode, indicating the high conductivity of the modified sensor and verifying the data observed using the CV technique. Surface descriptions were determined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The variation in the concentration of LV (2.0 to 1000 µM) was considered in BR buffer (pH = 5.0) at a scan rate (SR) of 10 mV/s by the NFS/CPE. The detection and quantification limits were 0.09 µM and 0.30 µM, respectively. To evaluate the application of LV in real samples, this procedure was established on Quinostarmax 500 mg tablets and human plasma samples. Reasonable results were obtained for the detection of LV.

Asunto(s)

RESUMEN

A novel environmental nano-catalyst based on zeolite (ZE) adjusted with carbon nanotube/silver nanoparticles (Ag/CNT) ornamented carbon paste electrode (CPE) is used for electrochemical oxidation of propylene glycol (PG) in 0.5 M H2SO4 solution. The techniques like cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) are utilized to achieve the catalytic activity performance. Surface characteristics are achieved by means of scanning electron microscope (SEM) and Energy dispersive X-ray analysis (EDX) techniques. Enhancing the loading magnitude of CNT into catalyst's ingredient can meaningfully develop the catalytic activity of the electrocatalyst towards propylene oxidation. The impact of altering the concentration of propylene glycol and the scanning rate on the resulting electrocatalyst performance during the oxidation cycle is considered. Chronoamperograms present an amplify of the steady state oxidation current density values after addition of these nano-catalysts. A promising catalytic stability of nano-catalyst has been achieved in electing its use for propylene glycol electro-oxidation in fuel cells applications.

RESUMEN

Three sensitive, accurate and precise HPLC methods were devolved for the simultaneous determination of vilazodone HCl (VILHC), agomelatine (AGO) or duloxetine HCl (DULHC) and vitamin B12 (cyanocoblamine B12) in bulk, pharmaceutical dosage form and in urine samples. Both similar methods (I and II) were carried out using 0.04 M phosphate buffer (pH 7.0), acetonitrile and methanol in the ratio (30:30:40, v/v) as a mobile phase. Thermo BDS hypersil-C18 column, with 5 µm particle size and 250 × 4.5 mm dimensions, at flow rate 1.0 mL min-1 and UV detection at 277 nm at ambient temperature 25 °C were used. The retention times were 5.12 and 2.54 min for VILHC and vitamin B12, 4.98 and 2.53 min for AGO and vitamin B12, respectively, with linearity range from 0.001 to 200 µg mL-1. However, for the separation of DULHC and B12, UV detection at 230 nm and Agilent Eclipse XDA-C8 (150 × 4.5 mm, 5 µm) column, were used (method III). The retention time of DULHC and vitamin B12 was found to be 4.53 and 1.35 min, respectively, with linearity range from 0.0005 to 200 µg mL-1. The proposed methods were validated as per the ICH guideline with very low LOD and LOQ. The values of %RSD for precision was less than 2% and the value of % recovery were found to be 99.20-100.9% and 99.23-100.67% for determination of the drugs in pure and pharmaceutical formulations, respectively, for all methods confirming that the methods are precise, accurate and selective for separation and determination of VILHC, AGO or DULHC from B12 in tablets and in urine samples without any interference from each other or from common excipients.

Asunto(s)

RESUMEN

It appeared that either the carbon paste or the screen-printed carbon electrodes that were modified with gold nanoparticles (AuNPs) gave rise to the largest current responses after a rapid screening of various nanomaterials as modifiers of carbon composite electrodes in view of designing an electrochemical sensor for Moxifloxacin Hydrochloride (Moxi). The screen-printed electrode (SPE) support was preferred over the carbon paste one for its ability to be used as disposable single-use sensor enabling the circumvention of the problems of surface fouling encountered in the determination of Moxi. The response of AuNPs modified SPE to Moxi was investigated by cyclic voltammetry (CV) (including the effect of the potential scan rate and the pH of the medium), chronoamperometry, and differential pulse voltammetry (DPV) after morphological and physico-chemical characterization. DPV was finally applied to Moxi detection in phosphate buffer at pH 7, giving rise to an accessible concentration window ranging between 8 µM and 0.48 mM, and the detection and quantification limits were established to be 11.6 µM and 38.6 µM, correspondingly. In order to estimate the applicability of Moxi identification scheme in actual trials, it was practiced in a human baby urine sample with excellent recoveries between 99.8 % and 101.6 % and RSDs of 1.1-3.4%, without noticeable interference.

RESUMEN

A new low-cost green electrochemical sensor based on nontoxic polyethylene glycol (PEG) and silver nanoparticles was used to improve the sensitivity of the carbon paste electrode for the investigation of olanzapine (OLZ) in dosage arrangements and in the existence of its coadministered drug fluoxetine and in the drug formulation. Scanning electron microscopy measurements were carried out to emphasize the morphology of the electrode surface. Cyclic voltammetry and differential pulse voltammetry were used to explore the diffusion and linearity behaviors of OLZ. Impedance spectroscopy measurements were determined to investigate the ac behavior of OLZ and then an ideal electrical circuit was modeled. A linear calibration was obtained from 1.0 × 10-8 to 1.25 × 10-4 M. The limit of detection was 1.5 × 10-9 M, whereas the limit of quantification was 5 × 10-9 M. The way has been wholly authenticated concerning linearity, precision, accuracy, reproducibility, sensitivity, and selectivity.

RESUMEN

Graphene oxide nanoparticles/polythreonine polymer as a nano-coating on AZ91E Mg alloy was considered as a new temporary implant for gastrectomy applications. This coating as a novel one is decomposable and has bio-viability possessions. Various electrochemical measurements were utilized for corrosion performance estimation of Mg alloy in peritoneal fluid with time of dipping. It was recognized that the nano-coating is fixed for 20 days giving unexpected high corrosion resistance. All experimental outcomes were verified by scanning electron microscope (SEM) and Energy dispersive X-ray (EDX) techniques. Moreover, in vitro antibacterial, and cytotoxicity of metal with and/or without coating utilizing MTT assay for cell viability analysis were achieved.

Asunto(s)

RESUMEN

A novel sensitive electrochemical sensor for microRNAlet-7a detection in normal serum samples, hepatocellular carcinoma patients and human liver cancer cells, has been excellently synthesized. The sensor constructed of carbon paste (CP) amended with silver nanoparticles (AgNPs) and extracted propolis (bee glue). The AgNPs/P modified carbon paste electrode (APCPE) displayed a high electrocatalytic activity in a Britton Robinson (BR) buffer (pH = 7.4). The techniques utilized to prepare this work are square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Surface characteristics were achieved using scanning (SEM), Fourier-transform infrared spectroscopy (FTIR), Spectrophotometer, transmission (TEM) electron microscope, energy dispersive X-ray analysis (EDX) and elemental mapping (EM) techniques. Under optimal conditions, the suggested sensor exhibits good rapid and sensible response reaching a very low detection limit of 10-3 femtomolar.

Asunto(s)

RESUMEN

A new sensitive simple electrochemical sensor for Moxifloxacin Hydrochloride (MOXI) detection has been successfully performed. The sensor built on carbon paste (CP) modified with silver nanoparticles (AgNPs). AgNPs are biocompatible stable noble materials especially in biological sensing. The silver nanoparticles modified carbon paste electrode (SNMCPE) displayed high electrocatalytic activity towards oxidation of 1.0mM MOXI in Britton Robinson (BR) buffer of pH range (2.0-9.0). The techniques used to do this work are cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). Surface characteristics were achieved using scanning electron microscopic (SEM) and Energy Dispersive X-Ray Analysis (EDX) techniques. The effect of changing MOXI concentration (7.0×10-7 to 1.8×10-4M) was studied in BR buffer (pH =7.4) at a scan rate of 50mV/s using SNMCPE. The detection and quantification limits were found to be 2.9×10-9M and 9.6×10-8M, respectively. In order to assess the applicability of MOXI detection method in real samples; this method was tested in Delmoxa tablet and human urine sample. Good sensible results were attained for MOXI detection.

Asunto(s)

RESUMEN

A novel system of electrodeposited gold nanoparticles on a carbon paste electrode was utilized as an electrochemical sensor to monitor the corrosion performance of 316L stainless steel alloy in aqueous humor containing moxifloxacin hydrochloride (MFH) drug. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and potentiodynamic polarization measurements were used to estimate the corrosion performance of 316L stainless steel alloy in aqueous humor with immersion time. The experimental data was confirmed by scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and antibacterial activity. All techniques conform well to each other and confirmed that the tested alloy corrosion decreases with increasing immersion time in aqueous humor. Corrosion is more inhibited after the addition of MFH drug. In addition, as the concentration of the drug increases, the protection efficiency of the tested alloy increases. This behavior was confirmed by sensing the drug concentration with time using the modified carbon paste electrode.

RESUMEN

A ruthenium complex was prepared and structurally characterized using various techniques. Antibacterial and antifungal activities of ruthenium complex were evaluated. High significant antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans was recorded. Minor cytotoxicity records were reported at the highest concentration level using MTT assay. The influence of Cu(II), Cr(III), Fe(III) and Ru(III) metal ions of salen Schiff base on the corrosion resistance of Ti-alloy in 0.5M HCl was studied. In vitro corrosion resistance was investigated using electrochemical impedance spectroscopy (EIS) measurements and confirmed by surface examination via scanning electron microscope (SEM) technique. Both impedance and phase angle maximum (θ(max)) values were at maximum in the case of the ruthenium complex with promising antibacterial and antifungal activities. The surface film created by the ruthenium complex was highly resistant against attack or deterioration by bacteria. The EIS study showed high impedance values for the ruthenium complex with increasing exposure time up to 8 days. SEM images showed uniform distribution and adsorption of Ru(III) ions on Ti-alloy surface. The ruthenium complex, as a model of organic-inorganic hybrid complex, offered new prospects with desired properties in industrial and medical applications.

Asunto(s)