scholarly journals Assay of Phospholipase D Activity by an Amperometric Choline Oxidase Biosensor

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1304 ◽  
Author(s):  
Rosanna Ciriello ◽  
Antonio Guerrieri
Keyword(s):  
Phospholipase D ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Fast Response ◽  
Borate Buffer ◽  
Choline Oxidase ◽  
Linear Calibration ◽  
Real Sample Analysis ◽  
Polypyrrole Film ◽  
Overoxidized Polypyrrole

A novel electrochemical method to assay phospholipase D (PLD) activity is proposed based on the employment of a choline biosensor realized by immobilizing choline oxidase through co-crosslinking on an overoxidized polypyrrole film previously deposited on a platinum electrode. To perform the assay, an aliquot of a PLD standard solution is typically added to borate buffer containing phosphatidylcholine at a certain concentration and the oxidation current of hydrogen peroxide is then measured at the rotating modified electrode by applying a detection potential of +0.7 V vs. SCE. Various experimental parameters influencing the assay were studied and optimized. The employment of 0.75% (v/v) Triton X-100, 0.2 mM calcium chloride, 5 mM phosphatidylcholine, and borate buffer at pH 8.0, ionic strength (I) 0.05 M allowed to achieve considerable current responses. In order to assure a controlled mass transport and, at the same time, high sensitivity, an electrode rotation rate of 200 rpm was selected. The proposed method showed a sensitivity of 24 (nA/s)⋅(IU/mL)−1, a wide linear range up to 0.33 IU/mL, fast response time and appreciable long-term stability. The limit of detection, evaluated from the linear calibration curve, was 0.005 IU/mL (S/N = 3). Finally, due to the presence of overoxidized polypyrrole film characterized by notable rejection properties towards electroactive compounds, a practical application to real sample analysis can be envisaged.

scholarly journals Nanostructured carbon electrode modified with N-doped graphene quantum dots–chitosan nanocomposite: a sensitive electrochemical dopamine sensor

2017 ◽  
Vol 4 (11) ◽  
pp. 171199 ◽  
Author(s):  
Sami Ben Aoun
Keyword(s):  
Quantum Dots ◽  
Hydrothermal Reaction ◽  
Limit Of Detection ◽  
Graphene Quantum Dots ◽  
High Sensitivity ◽  
Carbon Electrode ◽  
Limit Of Quantification ◽  
Real Sample Analysis ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene

A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dots–chitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwave-assisted hydrothermal reaction of glucose, and nitrogen doping was realized by introducing ammonia in the reaction mixture. Chitosan incorporation played a significant role towards the selectivity of the prepared sensor by hindering the ascorbic acid interference and enlarging the peak potential separation between dopamine and uric acid. The proposed sensor's performance was shown to be superior to several recently reported investigations. The as-prepared CS/N,GQDs@SPCE exhibited a high sensitivity (i.e. ca. 418 µA mM cm −2 ), a wide linear range i.e. (1–100 µM) and (100–200 µM) with excellent correlations (i.e. R 2  = 0.999 and R 2  = 1.000, respectively) and very low limit of detection (LOD = 0.145 µM) and limit of quantification (LOQ = 0.482 µM) based on S / N  = 3 and 10, respectively. The applicability of the prepared sensor for real sample analysis was tested by the determination of dopamine in human urine in pH 7.0 PBS showing an approximately 100% recovery with RSD < 2% inferring both the practicability and reliability of CS/N,GQDs@SPCE. The proposed sensor is endowed with high reproducibility (i.e. RSD = ca. 3.61%), excellent repeatability (i.e. ca. 0.91% current change) and a long-term stability (i.e. ca. 94.5% retained activity).

scholarly journals Electrochemical detection of chlorpheniramine maleate in the presence of an anionic surfactant and its analytical applications

2017 ◽  
Vol 95 (5) ◽  
pp. 553-559 ◽  
Author(s):  
Nagaraj Shetti ◽  
Deepti Nayak
Keyword(s):  
Anionic Surfactant ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Linear Calibration ◽  
Chlorpheniramine Maleate ◽  
Point Of Interest ◽  
Wave Voltammetry ◽  
Diffusion Controlled ◽  
Charge Transfer Coefficient

Improvement of methods for the detection of an analyte at a low concentration with high sensitivity has become an important point of interest. An effort has been made to know the electrochemical behavior of chlorpheniramine maleate in the presence of an anionic surfactant. Voltammograms were obtained in the range of 6.0–11.2 pH, and the maximum peak current (IP) was observed at pH 10.4. Various physicochemical parameters were estimated, including the process on the surface of the electrode, which was found to be diffusion controlled, heterogeneous rate constant, number of electrons transferred, and charge transfer coefficient. Square wave voltammetry of chlorpheniramine maleate at the modified electrode exhibited a linear calibration curve in the concentration range of 1.0–100 μmol/L, with a limit of detection of 28 nmol/L. The proposed technique was successfully used for the determination of chlorpheniramine maleate in pharmaceuticals, as well as in biological samples.

scholarly journals Potentiometric Signal Transduction for Selective Determination of 1-(3-Chlorophenyl)piperazine “Legal Ecstasy” Through Biomimetic Interaction Mechanism

Chemosensors ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 46
Author(s):  
Eman El-Naby
Keyword(s):  
Dynamic Range ◽  
Limit Of Detection ◽  
Interaction Mechanism ◽  
High Sensitivity ◽  
Fast Response ◽  
Polymeric Membrane ◽  
Selective Determination ◽  
Sensitivity And Selectivity ◽  
Pharmacologically Active

1-(3-chlorophenyl)piperazine (mCPP) is a wide spread new psychoactive substance produces stimulant and hallucinogenic effects similar to those sought from ecstasy. Hence, in the recent years, mCPP has been introduced by the organized crime through the darknet as a part of the illicit ecstasy market with a variable complex profile of pharmacologically active substances that pose problematic risk patterns among people who take these seized products. Accordingly, the design of selective sensors for the determination of mCPP is a very important demand. In this respect, a supramolecular architecture; [Na(15-crown-5)][BPh4] from the assembly of 15-crown-5 and sodium tetraphenylboron has been utilized as an ionophore, for the first time in the selective recognition of mCPP in conjunction with potassium tetrakis(p-chlorophenyl)borate and dioctylphthalate through polymeric membrane ion sensors. The ionophore exhibited a strong binding affinity that resulted in a high sensitivity with a slope closed to the ideal Nernstian value; 58.9 ± 0.43 mV/decade, a larger dynamic range from 10−6 to 10−2 M, a lower limit of detection down to 5.0 × 10−7 M and a fast response time of 5 s. Very important also is it was afforded excellent selectivity towards mCPP over psychoactive substances of major concern, providing a potentially useful system for the determination of mCPP in the illicit market. On comparison with the natural β-cyclodextrin as an ionophore, it exhibited more sensitivity and selectivity estimated to be the superior.

scholarly journals Exploiting a new europium(III) coordination polymer based on a zwitterionic ligand as a fluorescent probe for uranyl cations

2020 ◽  
pp. 174751982093226
Author(s):  
Bin Cai ◽  
Yu-Ning Meng ◽  
Meng-En Zhu ◽  
Youming Yang
Keyword(s):  
Infrared Spectroscopy ◽  
Thermogravimetric Analysis ◽  
Coordination Polymer ◽  
High Selectivity ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Fast Response ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray

Two new isostructural lanthanide(III) coordination polymers based on an unreported zwitterionic ligand, namely, [Ln(ox)(L)]n (ox = oxalate, HL = N,N'-dipropionic acid imidazolium, Ln = Eu or La), are synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. The fluorescence properties of the europium coordination polymer are investigated. In addition, the europium-based coordination polymer is utilized for specific sensing of UO22+ ions, showing high selectivity, a fast response time (8 min) and high sensitivity with noticeable quenching ( Ksv = 6.19 × 104 M−1) and limit of detection of 1.95 µM.

scholarly journals A Crosstalk- and Interferent-Free Dual Electrode Amperometric Biosensor for the Simultaneous Determination of Choline and Phosphocholine

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3545
Author(s):  
Rosanna Ciriello ◽  
Antonio Guerrieri
Keyword(s):  
Simultaneous Determination ◽  
High Resolution Mass Spectrometry ◽  
Limit Of Detection ◽  
Tissue Growth ◽  
Choline Oxidase ◽  
Amperometric Biosensor ◽  
Pt Electrode ◽  
Overoxidized Polypyrrole ◽  
Resolution Mass

Choline (Ch) and phosphocholine (PCh) levels in tissues are associated to tissue growth and so to carcinogenesis. Till now, only highly sophisticated and expensive techniques like those based on NMR spectroscopy or GC/LC- high resolution mass spectrometry permitted Ch and PCh analysis but very few of them were capable of a simultaneous determination of these analytes. Thus, a never reported before amperometric biosensor for PCh analysis based on choline oxidase and alkaline phosphatase co-immobilized onto a Pt electrode by co-crosslinking has been developed. Coupling the developed biosensor with a parallel sensor but specific to Ch, a crosstalk-free dual electrode biosensor was also developed, permitting the simultaneous determination of Ch and PCh in flow injection analysis. This novel sensing device performed remarkably in terms of sensitivity, linear range, and limit of detection so to exceed in most cases the more complex analytical instrumentations. Further, electrode modification by overoxidized polypyrrole permitted the development of a fouling- and interferent-free dual electrode biosensor which appeared promising for the simultaneous determination of Ch and PCh in a real sample.

scholarly journals Modified Nickel Nanowires for Electro-Catalytic Oxidation of Formaldehyde in Alkaline Solutions

Proceedings ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 43
Author(s):  
Špela Trafela ◽  
Kristina Žužek Rožman
Keyword(s):  
Cyclic Voltammetry ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Fast Response ◽  
Alkaline Media ◽  
Alkaline Solutions ◽  
Nickel Nanowires ◽  
Transmission Electron ◽  
Electro Oxidation ◽  
Electro Catalytic Oxidation

A Ni nanowires-based electrodes for formaldehyde (HCHO) detection were fabricated via a template-assisted electrodeposition. The as-deposited Ni nanowires (NWs) were characterized by scanning electron microscope (SEM). In order to form an active redox couple of Ni(OH)2/NiOOH on the surface of nanowires, the Ni NWs were electrochemically modified in 0.5 mol L−1 KOH using cyclic voltammetry. The presence of Ni(OH)2/NiOOH on the surface of Ni NWs was confirmed by transmission electron microscopy (TEM). Furthermore, the ability of modified Ni NWs-based electrode (i.e., receptor element) was investigated for HCHO electro-oxidation in alkaline media via cyclic voltammetry and amperometry. The fabricated Ni NWs-based electrode exhibited fast response (3s), good selectivity, a high sensitivity and low limit of detection 0.8 μmol L−1.

scholarly journals Highly Sensitive Amperometric Detection of Hydrogen Peroxide in Saliva Based on N-Doped Graphene Nanoribbons and MnO2 Modified Carbon Paste Electrodes

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8301
Author(s):  
Ema Gričar ◽  
Kurt Kalcher ◽  
Boštjan Genorio ◽  
Mitja Kolar
Keyword(s):  
Hydrogen Peroxide ◽  
Limit Of Detection ◽  
Graphene Nanoribbons ◽  
Amperometric Detection ◽  
High Sensitivity ◽  
Pharmaceutical Product ◽  
Carbon Paste ◽  
Real Sample Analysis ◽  
Starting Point ◽  
Highly Sensitive

Four different graphene-based nanomaterials (htGO, N-htGO, htGONR, and N-htGONR) were synthesized, characterized, and used as a modifier of carbon paste electrode (CPE) in order to produce a reliable, precise, and highly sensitive non-enzymatic amperometric hydrogen peroxide sensor for complex matrices. CPE, with their robustness, reliability, and ease of modification, present a convenient starting point for the development of new sensors. Modification of CPE was optimized by systematically changing the type and concentration of materials in the modifier and studying the prepared electrode surface by cyclic voltammetry. N-htGONR in combination with manganese dioxide (1:1 ratio) proved to be the most appropriate material for detection of hydrogen peroxide in pharmaceutical and saliva matrices. The developed sensor exhibited a wide linear range (1.0–300 µM) and an excellent limit of detection (0.08 µM) and reproducibility, as well as high sensitivity and stability. The sensor was successfully applied to real sample analysis, where the recovery values for a commercially obtained pharmaceutical product were between 94.3% and 98.0%. Saliva samples of a user of the pharmaceutical product were also successfully analyzed.

Enzymatic fluorometric procedure for phospholipid quantification with an automated microtiter plate fluorometer

1991 ◽  
Vol 37 (6) ◽  
pp. 868-874 ◽  
Author(s):  
M Nazeem Nanjee ◽  
Abraham K Gebre ◽  
Norman E Miller
Keyword(s):  
Phospholipase D ◽  
Limit Of Detection ◽  
Total Phospholipid ◽  
Microtiter Plate ◽  
Inorganic Phosphorus ◽  
Choline Oxidase ◽  
Fluorometric Detection ◽  
Acid Digestion ◽  
Reaction Sequence ◽  
Catalyzed Oxidation

Abstract We describe a new enzymatic assay for phospholipids that is rapid, sensitive, convenient, and inexpensive. The method is based on the fluorometric detection of H2O2, generated by the choline oxidase-catalyzed oxidation of choline, after liberation of choline from phospholipids by phospholipase D. Significant advantages over existing methods are that the entire reaction sequence can take place in a single vessel, a 12 x 8 well microtiter plate, and that the fluorescence intensity can be measured automatically with a Fluoroskan II (Labsystems Oy) detector. Extracting samples with organic solvents is unnecessary, although the method can be applied to extracts in isopropanol. The assay is approximately 60-fold more sensitive and has a limit of detection eightfold lower than currently available enzymatic colorimetric methods. Including solvent blanks, eight standards, and three quality-control pools, 34 samples can be pipetted and assayed in duplicate in 60 min. Results obtained by this procedure for total phospholipid choline in lipoproteins in primate plasma agreed well with those obtained for inorganic phosphorus by the Bartlett acid-digestion procedure.

scholarly journals Tin Disulfide-Coated Microfiber for Humidity Sensing with Fast Response and High Sensitivity

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 648
Author(s):  
Aijie Liang ◽  
Jingyuan Ming ◽  
Wenguo Zhu ◽  
Heyuan Guan ◽  
Xinyang Han ◽  
...  
Keyword(s):  
Humidity Sensor ◽  
Small Diameter ◽  
High Sensitivity ◽  
Large Change ◽  
Small Variation ◽  
Response Speed ◽  
Fast Response ◽  
Tin Disulfide ◽  
Recovery Times ◽  
Response And Recovery

Breath monitoring is significant in assessing human body conditions, such as cardiac and pulmonary symptoms. Optical fiber-based sensors have attracted much attention since they are immune to electromagnetic radiation, thus are safe for patients. Here, a microfiber (MF) humidity sensor is fabricated by coating tin disulfide (SnS2) nanosheets onto the surface of MF. The small diameter (~8 μm) and the long length (~5 mm) of the MF promise strong interaction between guiding light and SnS2. Thus, a small variation in the relative humidity (RH) will lead to a large change in optical transmitted power. A high RH sensitivity of 0.57 dB/%RH is therefore achieved. The response and recovery times are estimated to be 0.08 and 0.28 s, respectively. The high sensitivity and fast response speed enable our SnS2-MF sensor to monitor human breath in real time.

scholarly journals Ratiometric Fluorescent Biosensors for Glucose and Lactate Using an Oxygen-Sensing Membrane

Biosensors ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 208
Author(s):  
Hong Dinh Duong ◽  
Jong Il Rhee
Keyword(s):  
Limit Of Detection ◽  
Oxygen Sensing ◽  
High Sensitivity ◽  
Glucose Sensing ◽  
Oxidation Reactions ◽  
Lactate Oxidase ◽  
Lactate Oxidation ◽  
Detection Range ◽  
Quenching Effect ◽  
Sensing Membrane

In this study, ratiometric fluorescent glucose and lactate biosensors were developed using a ratiometric fluorescent oxygen-sensing membrane immobilized with glucose oxidase (GOD) or lactate oxidase (LOX). Herein, the ratiometric fluorescent oxygen-sensing membrane was fabricated with the ratio of two emission wavelengths of platinum meso-tetra (pentafluorophenyl) porphyrin (PtP) doped in polystyrene particles and coumarin 6 (C6) captured into silica particles. The operation mechanism of the sensing membranes was based on (i) the fluorescence quenching effect of the PtP dye by oxygen molecules, and (ii) the consumption of oxygen levels in the glucose or lactate oxidation reactions under the catalysis of GOD or LOX. The ratiometric fluorescent glucose-sensing membrane showed high sensitivity to glucose in the range of 0.1–2 mM, with a limit of detection (LOD) of 0.031 mM, whereas the ratiometric fluorescent lactate-sensing membrane showed the linear detection range of 0.1–0.8 mM, with an LOD of 0.06 mM. These sensing membranes also showed good selectivity, fast reversibility, and stability over long-term use. They were applied to detect glucose and lactate in artificial human serum, and they provided reliable measurement results.

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