scholarly journals DEVELOPMENT OF ARGININE DEIMINASE BASED CONDUCTOMETRIC BIOSENSOR FOR ARGININE DETERMINATION

2021 ◽  
Vol 18 (2) ◽  
pp. 4-13
Author(s):  
O. O. Soldatkin ◽  
I. S. Kucherenko ◽  
O. Ya. Sayapina ◽  
D. Yu. Kucherenko ◽  
S. V. Marchenko ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Buffer Capacity ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Arginine Deiminase ◽  
Real Samples ◽  
Covalent Crosslinking ◽  
Enzyme Biosensor ◽  
First Time ◽  
Conductometric Biosensor

For the first time, a conductometric enzyme biosensor was developed to determine arginine concentrations. The bioselective membrane of the biosensor was formed by immobilization of arginine deiminase on the surface of gold planar transducer using covalent crosslinking of glutaraldehyde with bovine serum albumin. An effect of the solution characteristics (ionic strength, buffer capacity) on the biosensor functioning was studied. The proposed monoenzyme biosensor was shown to have high sensitivity to arginine (minimum limit of detection - 5 μM) and good selectivity towards possible interferents. The linear range of determination was from 10 to 800 μM. The biosensor sensitivity to arginine is 72 μS /μM. The developed biosensor was demonstrated to be promising for the arginine analysis in real samples.

scholarly journals Pooled sputum to optimise the efficiency and utility of rapid, point-of-care molecular SARS-CoV-2 testing

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Alison Burdett ◽  
Christofer Toumazou ◽  
Rashmita Sahoo ◽  
Adam Mujan ◽  
Tsz-Kin Hon ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Point Of Care ◽  
High Sensitivity ◽  
Pool Size ◽  
Pooled Testing ◽  
Paired Samples ◽  
Absolute Strength ◽  
Potential Benefits ◽  
First Time ◽  
Multiple Patients

Abstract Background As SARS-CoV-2 testing expands, particularly to widespread asymptomatic testing, high sensitivity point-of-care PCR platforms may optimise potential benefits from pooling multiple patients’ samples. Method We tested patients and asymptomatic citizens for SARS-CoV-2, exploring the efficiency and utility of CovidNudge (i) for detection in individuals’ sputum (compared to nasopharyngeal swabs), (ii) for detection in pooled sputum samples, and (iii) by modelling roll out scenarios for pooled sputum testing. Results Across 295 paired samples, we find no difference (p = 0.1236) in signal strength for sputum (mean amplified replicates (MAR) 25.2, standard deviation (SD) 14.2, range 0–60) compared to nasopharyngeal swabs (MAR 27.8, SD 12.4, range 6–56). At 10-sample pool size we find some drop in absolute strength of signal (individual sputum MAR 42.1, SD 11.8, range 13–60 vs. pooled sputum MAR 25.3, SD 14.6, range 1–54; p < 0.0001), but only marginal drop in sensitivity (51/53,96%). We determine a limit of detection of 250 copies/ml for an individual test, rising only four-fold to 1000copies/ml for a 10-sample pool. We find optimal pooled testing efficiency to be a 12–3-1-sample model, yet as prevalence increases, pool size should decrease; at 5% prevalence to maintain a 75% probability of negative first test, 5-sample pools are optimal. Conclusion We describe for the first time the use of sequentially dipped sputum samples for rapid pooled point of care SARS-CoV-2 PCR testing. The potential to screen asymptomatic cohorts rapidly, at the point-of-care, with PCR, offers the potential to quickly identify and isolate positive individuals within a population “bubble”.

scholarly journals ARGINASE-BASED AMPEROMETRIC BIOSENSOR FOR MANGANESE IONS ANALYSIS

2016 ◽  
Vol 1 ◽  
pp. 22-28 ◽  
Author(s):  
Nataliya Stasyuk ◽  
Mariya Synenka ◽  
Galina Gayda ◽  
Oleh Smutok ◽  
Mykhailo Gonchar
Keyword(s):  
Environmental Control ◽  
Limit Of Detection ◽  
Hansenula Polymorpha ◽  
High Sensitivity ◽  
Methylotrophic Yeast ◽  
Cost Effective ◽  
Metallic Ions ◽  
Actual Problem ◽  
Enzyme Biosensor ◽  
Manganese Compounds

The development of simple cost-effective sensitive enzymatic methods for analysis of toxic metallic ions is an actual problem. Promising tools for elaboration of such methods are Mn2+-dependent enzymes. A novel manganese(II)-sensitive amperometric bi-enzyme biosensor based on of recombinant human arginase I (arginase) isolated from the gene-engineered strain of methylotrophic yeast Hansenula polymorpha and commercial urease is described. The biosensing layer with urease and apo-enzyme of arginase was placed onto a polyaniline-Nafion composite platinum electrode. The developed sensor revealed a high sensitivity to Mn2+-ions – 9200±20 A/(M∙m2)with the apparent Michaelis-Menten constant derived from Mn2+-ions calibration curve of 11.5±1.0 µM. A linear concentration range was observed from 1 µM to 6,5 µM MnCl2, a limit of detection being of 0.15 µM and a response time – 2.5 min. The proposed biosensor may be useful to monitor manganese compounds in laboratories of medicine, food industry and environmental control service.

A potential reusable fluorescent aptasensor based on magnetic nanoparticles for ochratoxin A analysis

2019 ◽  
Vol 17 (1) ◽  
pp. 1301-1308 ◽  
Author(s):  
Pinzhu Qin ◽  
Dawei Huang ◽  
Zihao Xu ◽  
Ying Guan ◽  
Yongxin Bing ◽  
...  
Keyword(s):  
Magnetic Property ◽  
Ochratoxin A ◽  
Cost Reduction ◽  
Environmental Samples ◽  
Limit Of Detection ◽  
Specific Binding ◽  
High Sensitivity ◽  
Capture Probe ◽  
Real Samples ◽  
Fluorescent Aptasensor

AbstractAn aptasensor for the detection of ochratoxin A (OTA) in environmental samples was developed. It displayed high sensitivity and good selectivity. Factors such as specific binding between a FAM (5-carboxyfluorescein)-labeled aptamer (f-RP) and OTA, and a magnetic property of a streptavidin magbeads-modified capture probe (bm-CP) resulted in aptasensor’s linear relationship between fluorescence intensity and the concentration of OTA. This characteristic is present at the OTA concentration ranges from 0.100 μM to 25.00 μM with a LOD (limit of detection) of 0.0690 μM. The bm-CP can be reused through melting, washing and magnetic separation, which contributes to cost reduction. In addition, the proposed method is simple and detection process is fast. The aptasensor can be used in real samples.

scholarly journals A Simple Colorimetric and Fluorescent Sensor to Detect Organophosphate Pesticides Based on Adenosine Triphosphate-Modified Gold Nanoparticles

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4302 ◽  
Author(s):  
Xiaoxia Li ◽  
Haixin Cui ◽  
Zhanghua Zeng
Keyword(s):  
Gold Nanoparticles ◽  
Adenosine Triphosphate ◽  
Limit Of Detection ◽  
Fluorescent Sensor ◽  
Tap Water ◽  
High Reliability ◽  
High Sensitivity ◽  
Organophosphate Pesticides ◽  
Real Samples ◽  
Sensitivity And Selectivity

A simple and dual modal (colorimetric and fluorescent) sensor for organophosphate pesticides with high sensitivity and selectivity using adenosine triphosphate (ATP)- and rhodamine B-modified gold nanoparticles (RB-AuNPs), was successfully fabricated. This detection for ethoprophos afforded colorimetric and fluorescence imaging changes visualization. The quantitative determination was linearly proportional to the amounts of ethoprophos in the range of a micromolar scale (4.0–15.0 µM). The limit of detection for ethoprophos was as low as 37.0 nM at 3σ/k. Moreover, the extent application of this simple assay was successfully demonstrated in tap water samples with high reliability and applicability, indicating remarkable application in real samples.

SERUM TRIIODOTHYRONINE DETERMINATION BY SATURATION ANALYSIS

1973 ◽  
Vol 72 (4) ◽  
pp. 714-726 ◽  
Author(s):  
A. Burger ◽  
B. Miller ◽  
C. Sakoloff ◽  
M. B. Vallotton
Keyword(s):  
Ionic Strength ◽  
Limit Of Detection ◽  
Improved Method ◽  
Accuracy Of Measurement ◽  
Tracer Amount ◽  
The Mean ◽  
Physiological Values ◽  
Hyperthyroid Patients ◽  
Solvent Blank

ABSTRACT An improved method for the determination of serum triiodothyronine (T3) has been developed. After addition of a tracer amount of the hormone, T3 was extracted from 1 ml serum under conditions of pH and ionic strength which favoured T3 extraction (89%) over thyroxine (T4) extraction (58%). Chromatography of the extracted material on Sephadex LH-20 separated T3 completely from residual T4. The T3 eluate was dried, then re-dissolved in 0.5 ml NaOH 0.04 n. To 0.2 ml duplicate aliquots, a standard amount of TBG was added for the competitive protein analysis. After one hour incubation at 4°C, separation of bound from free T3 was achieved on small Sephadex G-25 columns. Overall recovery was 67 ± 10.8% and correction for the loss was made. The solvent blank was 37 ± 27 (sd) ng/100 ml. Accuracy of measurement of known quantities of T3 added to serum was 98.4%. The coefficient of variation within the assay was 6.2% and between the assays it was 11.4%. The limit of detection (0.1 ng) corresponded to a concentration of 25 ng/100 ml. T4 added to serum did not interfere with T3 determination until high non-physiological values were reached. The mean ± sd serum T3 in 54 euthyroid subjects was 153 ± 58 ng/100 ml and in 24 hyperthyroid patients it was 428 ±186 ng/100 ml; 4 out of the 24 hyperthyroid values were within 2 sd of the mean euthyroid group. All the values found in the euthyroid group were well above the limit of detection of the method.

Green Synthesis and Spectroscopic Studies of Ag-rGO Nanocomposites for Highly Selective Mercury (II) Sensing

2018 ◽  
Vol 9 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Shubhangi J. Mane-Gavade ◽  
Sandip R. Sabale ◽  
Xiao-Ying Yu ◽  
Gurunath H. Nikam ◽  
Bhaskar V. Tamhankar
Keyword(s):  
Green Synthesis ◽  
Color Change ◽  
Limit Of Detection ◽  
Aqueous Media ◽  
Suitable Condition ◽  
Cost Effective ◽  
Spectroscopic Studies ◽  
Calibration Plot ◽  
First Time

Introduction: Herein we report the green synthesis and characterization of silverreduced graphene oxide nanocomposites (Ag-rGO) using Acacia nilotica gum for the first time. Experimental: We demonstrate the Hg2+ ions sensing ability of the Ag-rGO nanocomposites form aqueous medium. The developed colorimetric sensor method is simple, fast and selective for the detection of Hg2+ ions in aqueous media in presence of other associated ions. A significant color change was noticed with naked eye upon Hg2+ addition. The color change was not observed for cations including Sr2+, Ni2+, Cd2+, Pb2+, Mg2+, Ca2+, Fe2+, Ba2+ and Mn2+indicating that only Hg2+ shows a strong interaction with Ag-rGO nanocomposites. Under the most suitable condition, the calibration plot (A0-A) against concentration of Hg2+ was linear in the range of 0.1-1.0 ppm with a correlation coefficient (R2) value 0.9998. Results & Conclusion The concentration of Hg2+ was quantitatively determined with the Limit of Detection (LOD) of 0.85 ppm. Also, this method shows excellent selectivity towards Hg2+ over nine other cations tested. Moreover, the method offers a new cost effective, rapid and simple approach for the detection of Hg2+ in water samples.

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.

scholarly journals Ag nanoparticles outperform Au nanoparticles for the use as label in electrochemical point-of-care sensors

2021 ◽  
Author(s):  
Franziska Beck ◽  
Carina Horn ◽  
Antje J. Baeumner
Keyword(s):  
Limit Of Detection ◽  
Point Of Care ◽  
Automatic Measurement ◽  
High Sensitivity ◽  
Differential Pulse ◽  
Small Sample ◽  
Blood Protein ◽  
User Friendliness ◽  
Response Curves ◽  
Assay Protocol

AbstractElectrochemical immunosensors enable rapid analyte quantification in small sample volumes, and have been demonstrated to provide high sensitivity and selectivity, simple miniaturization, and easy sensor production strategies. As a point-of-care (POC) format, user-friendliness is equally important and most often not combinable with high sensitivity. As such, we demonstrate here that a sequence of metal oxidation and reduction, followed by stripping via differential pulse voltammetry (DPV), provides lowest limits of detection within a 2-min automatic measurement. In exchanging gold nanoparticles (AuNPs), which dominate in the development of POC sensors, with silver nanoparticles (AgNPs), not only better sensitivity was obtained, but more importantly, the assay protocol could be simplified to match POC requirements. Specifically, we studied both nanoparticles as reporter labels in a sandwich immunoassay with the blood protein biomarker NT-proBNP. For both kinds of nanoparticles, the dose-response curves easily covered the ng∙mL−1 range. The mean standard deviation of all measurements of 17% (n ≥ 4) and a limit of detection of 26 ng∙mL−1 were achieved using AuNPs, but their detection requires addition of HCl, which is impossible in a POC format. In contrast, since AgNPs are electrochemically less stable, they enabled a simplified assay protocol and provided even lower LODs of 4.0 ng∙mL−1 in buffer and 4.7 ng∙mL−1 in human serum while maintaining the same or even better assay reliability, storage stability, and easy antibody immobilization protocols. Thus, in direct comparison, AgNPs clearly outperform AuNPs in desirable POC electrochemical assays and should gain much more attention in the future development of such biosensors.

Analytical assessment of ortho clinical diagnostics high-sensitivity cardiac troponin I assay

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Peter A. Kavsak ◽  
Tara Edge ◽  
Chantele Roy ◽  
Paul Malinowski ◽  
Karen Bamford ◽  
...  
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Limit Of Detection ◽  
Clinical Performance ◽  
Characteristic Curve ◽  
Area Under The Curve ◽  
High Sensitivity ◽  
Cardiac Troponin I ◽  
Clinical Diagnostics ◽  
Ortho Clinical Diagnostics

AbstractObjectivesTo analytically evaluate Ortho Clinical Diagnostics VITROS high-sensitivity cardiac troponin I (hs-cTnI) assay in specific matrices with comparison to other hs-cTn assays.MethodsThe limit of detection (LoD), imprecision, interference and stability testing for both serum and lithium heparin (Li-Hep) plasma for the VITROS hs-cTnI assay was determined. We performed Passing-Bablok regression analyses between sample types for the VITROS hs-cTnI assay and compared them to the Abbott ARCHITECT, Beckman Access and the Siemens ADVIA Centaur hs-cTnI assays. We also performed Receiver-operating characteristic curve analyses with the area under the curve (AUC) determined in an emergency department (ED)-study population (n=131) for myocardial infarction (MI).ResultsThe VITROS hs-cTnI LoD was 0.73 ng/L (serum) and 1.4 ng/L (Li-Hep). Stability up to five freeze-thaws was observed for the Ortho hs-cTnI assay, with the analyte stability at room temperature in serum superior to Li-Hep with gross hemolysis also affecting Li-Hep plasma hs-cTnI results. Comparison of Li-Hep to serum concentrations (n=202), yielded proportionally lower concentrations in plasma with the VITROS hs-cTnI assay (slope=0.85; 95% confidence interval [CI]:0.83–0.88). In serum, the VITROS hs-cTnI concentrations were proportionally lower compared to other hs-cTnI assays, with similar slopes observed between assays in samples frozen <−70 °C for 17 years (ED-study) or in 2020. In the ED-study, the VITROS hs-cTnI assay had an AUC of 0.974 (95%CI:0.929–0.994) for MI, similar to the AUCs of other hs-cTn assays.ConclusionsLack of standardization of hs-cTnI assays across manufacturers is evident. The VITROS hs-cTnI assay yields lower concentrations compared to other hs-cTnI assays. Important differences exist between Li-Hep plasma and serum, with evidence of stability and excellent clinical performance comparable to other hs-cTn assays.

scholarly journals Confirming putative variants at ≤ 5% allele frequency using allele enrichment and Sanger sequencing

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yan Helen Yan ◽  
Sherry X. Chen ◽  
Lauren Y. Cheng ◽  
Alyssa Y. Rodriguez ◽  
Rui Tang ◽  
...  
Keyword(s):  
Sanger Sequencing ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Sequencing Errors ◽  
Whole Exome ◽  
Formalin Fixed Paraffin ◽  
Formalin Fixed Paraffin Embedded ◽  
Fresh Frozen ◽  
The Cost ◽  
Allelic Fraction

AbstractWhole exome sequencing (WES) is used to identify mutations in a patient’s tumor DNA that are predictive of tumor behavior, including the likelihood of response or resistance to cancer therapy. WES has a mutation limit of detection (LoD) at variant allele frequencies (VAF) of 5%. Putative mutations called at ≤ 5% VAF are frequently due to sequencing errors, therefore reporting these subclonal mutations incurs risk of significant false positives. Here we performed ~ 1000 × WES on fresh-frozen and formalin-fixed paraffin-embedded (FFPE) tissue biopsy samples from a non-small cell lung cancer patient, and identified 226 putative mutations at between 0.5 and 5% VAF. Each variant was then tested using NuProbe NGSure, to confirm the original WES calls. NGSure utilizes Blocker Displacement Amplification to first enrich the allelic fraction of the mutation and then uses Sanger sequencing to determine mutation identity. Results showed that 52% of the 226 (117) putative variants were disconfirmed, among which 2% (5) putative variants were found to be misidentified in WES. In the 66 cancer-related variants, the disconfirmed rate was 82% (54/66). This data demonstrates Blocker Displacement Amplification allelic enrichment coupled with Sanger sequencing can be used to confirm putative mutations ≤ 5% VAF. By implementing this method, next-generation sequencing can reliably report low-level variants at a high sensitivity, without the cost of high sequencing depth.

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