scholarly journals Amperometric Biosensor Based on Coimmobilization of Multiwalled Carbon Nanotubes and Horseradish Peroxidase-Gold Nanocluster Bioconjugates for Detecting H2O2

2020 ◽  
Vol 2020 ◽  
pp. 1-6 ◽  
Author(s):  
Qiong-Qiong Ren ◽  
Fen Yang ◽  
Wu Ren ◽  
Chang Wang ◽  
Wen-Shuai Jiang ◽  
...  
Keyword(s):  
Horseradish Peroxidase ◽  
Gold Nanoclusters ◽  
Calf Serum ◽  
Amperometric Biosensor ◽  
Serum Samples ◽  
Multiwalled Carbon ◽  
Gold Nanocluster ◽  
Amperometric Sensors ◽  
Long Term Stability

An enzyme-based amperometric biosensor was fabricated for detecting hydrogen peroxide (H2O2). Horseradish peroxidase (HRP) was modified using functionalized fluorescent gold nanoclusters (AuNCs) via biomineralization. HRP-AuNCs were successfully immobilized on multiwalled carbon nanotube- (MWCNT-) coated carbon fiber ultramicroelectrodes (CFUMEs). The AuNCs, which act as molecular electric wires, effectively promote the electron transfer between the enzyme active center and the electrode. Additionally, the HRP conjugated with the AuNCs retains its biological activity, which enables the catalytic reaction of H2O2. The HRP-AuNCs/MWCNTs/CFUMEs have been proven as excellent amperometric sensors for H2O2. The sensitivity of the H2O2 biosensor is 3.0×10−4 A/M, and the detection limit is estimated to be 443 nM. Furthermore, the biosensor exhibited long-term stability and good reproducibility. Moreover, the biosensor has been tested by determining the H2O2 concentration in calf serum samples.

scholarly journals An updated protocol based on CLSI document C37 for preparation of off-the-clot serum from individual units for use alone or to prepare commutable pooled serum reference materials

2020 ◽  
Vol 58 (3) ◽  
pp. 368-374 ◽  
Author(s):  
Uliana Danilenko ◽  
Hubert W. Vesper ◽  
Gary L. Myers ◽  
Patric A. Clapshaw ◽  
Johanna E. Camara ◽  
...  
Keyword(s):  
Human Serum ◽  
Reference Materials ◽  
Frozen Storage ◽  
Metrological Traceability ◽  
Medical Laboratory ◽  
Serum Samples ◽  
Long Term Stability ◽  
Individual Human

AbstractManufacturers of in vitro diagnostic medical devices, clinical laboratories, research laboratories and calibration laboratories require commutable reference materials that can be used in the calibration hierarchies of medical laboratory measurement procedures used for human specimens to establish metrological traceability to higher order reference systems. Commutable materials are also useful in external quality assessment surveys. In order to achieve these goals, matrix-based reference materials with long-term stability, appropriate measurand concentrations and commutability with individual human specimens are required. The Clinical and Laboratory Standards Institute (CLSI) guideline C37-A (now archived) provided guidance to prepare commutable pooled serum reference materials for use in the calibration hierarchies of cholesterol measurement procedures. Experience using the C37-A guideline has identified a number of technical enhancements as well as applications to measurands other than cholesterol. This experience is incorporated into this updated protocol to ensure the procedure will continue to meet the needs of the medical laboratory. The updated protocol describes a procedure for preparing frozen human serum units or pools with minimal matrix alterations that are likely to be commutable with individual human serum samples. The protocol provides step-by-step guidance for the planning phase, collection of individual serum units, processing the units, qualifying the units for use in a pool and frozen storage of aliquots of pooled sera to manufacture frozen serum pools. Guidance on how to perform quality control of the final product and suggestions on documentation are also provided.

PKP-008 Long term stability of trastuzumab in serum samples: Abstract PKP-008 Table 1

2016 ◽  
Vol 23 (Suppl 1) ◽  
pp. A181.2-A182
Author(s):  
J González García ◽  
F Gutiérrez Nicolás ◽  
GJ Nazco Casariego ◽  
MM Viña Romero ◽  
R Ramos Díaz ◽  
...  
Keyword(s):  
Serum Samples ◽  
Term Stability ◽  
Long Term Stability

Antibody Interference in a Two-Site Immunometnc Assay for Thyrotrophin

1989 ◽  
Vol 26 (4) ◽  
pp. 346-352 ◽  
Author(s):  
Rhys John ◽  
Robert Henley ◽  
Nicola Barron
Keyword(s):  
Horseradish Peroxidase ◽  
Thyroid Function ◽  
Calf Serum ◽  
Mouse Serum ◽  
Newborn Calf Serum ◽  
Serum Samples ◽  
Thyroid Function Testing ◽  
Function Testing

Of 1585 consecutive serum samples referred for thyroid function testing, 14 gave erroneously high values from a two-site immunoenzymometric assay for thyrotrophin. The addition of mouse or newborn calf serum to the assay failed to correct the interference. In serum samples from 11 patients who were available for follow up a higher concentration of mouse, but not of horse, sheep or rabbit scrum reduced the interference. The interference was associated only with assay systems which employed horseradish peroxidase but not 125I as a label. Addition of mouse serum and anti-IgM to the assay reagents successfully removed the interference.

Critical Evaluation of a New Flame Emission Analysis System, the "Klina Flame"

1972 ◽  
Vol 18 (9) ◽  
pp. 1005-1008 ◽  
Author(s):  
Richard J Schlesinger ◽  
Raymond A Lesonsky ◽  
Robert Lottritz
Keyword(s):  
Critical Evaluation ◽  
Paired Data ◽  
Serum Samples ◽  
Emission Analysis ◽  
Long Term Stability ◽  
Flame Emission ◽  
Analysis System ◽  
Instrumental Methods ◽  
Predictable Variation

Abstract Recently there have been several advances in instrumental methods for the flame emission analysis of electrolyte cations of clinical significance. Greater precision and increased ease of operation are among today’s clinical requirements. This study compares a new automated flame photometer, "Klina Flame" (Beckman Instruments) with a "Techtron-AA5" atomic absorption emission unit (Varian Instruments) and an "IL 143" flame system (Instrumentation Laboratory). Day-to-day variation between paired data over a three-month period showed comparable and explainable similarities and variations between the three instruments. Results of lithium determinations gave favorable comparison statistics. Long-term stability on all the systems were generally comparable. A comparison of manual vs. automatic modes of dilution with serum samples of various viscosities generally gave predictable variation for instruments of similar quality. The piston dilutor feature of the Klina system seems to prevent the variability seen at higher viscosities when the IL system is used, which has a peristaltic dilutor.

scholarly journals Additional factors influencing sensitivity in the tetramethyl benzidine method for horseradish peroxidase neurohistochemistry.

1980 ◽  
Vol 28 (11) ◽  
pp. 1255-1259 ◽  
Author(s):  
M M Mesulam ◽  
E Hegarty ◽  
H Barbas ◽  
K A Carson ◽  
E C Gower ◽  
...  
Keyword(s):  
Horseradish Peroxidase ◽  
Wheat Germ ◽  
Storage Medium ◽  
Neural Connections ◽  
Long Term Stability ◽  
Factors Influencing ◽  
Duration Of Storage ◽  
The Stability ◽  
Tetramethyl Benzidine

In experiments that use horseradish peroxidase (HRP) and tetramethyl benzidine (TMB) for tracing neural connections, the activity of tissue-bound enzyme as well as the stability of the resultant reaction product are influenced by the duration of storage, the composition of the storage medium, the type of counterstaining and even the details of histological dehydration. Furthermore, the conditions for preserving HRP activity are very different from those necessary for preserving the stability of the tetramethyl benzidine (TMB) reaction product. Thus, tissue-bound HRP activity is stable at a neutral pH, while a much lower pH, around 3.3, is required for preserving the stability of the TMB reaction product. Recent evidence indicates that the stabilization bath in sodium nitroferricyanide that was previously recommended is not necessary. However, gradual dehydration of mounted sections is essential for long-term stability. Excessive counterstaining and excessive dehydration interfere with the detection of reaction product. These considerations are pertinent to experiments using free HRP as well as to those where the enzyme has been conjugated to wheat germ agglutinin.

scholarly journals Provisional standardization of hepcidin assays: creating a traceability chain with a primary reference material, candidate reference method and a commutable secondary reference material

2019 ◽  
Vol 57 (6) ◽  
pp. 864-872 ◽  
Author(s):  
Laura E. Diepeveen ◽  
Coby M.M. Laarakkers ◽  
Gustavo Martos ◽  
Marta E. Pawlak ◽  
Fatih F. Uğuz ◽  
...  
Keyword(s):  
Reference Material ◽  
Clinical Laboratory ◽  
Isotope Dilution Mass Spectrometry ◽  
Reference Method ◽  
Serum Samples ◽  
Traceability Chain ◽  
Long Term Stability ◽  
Purity Analysis ◽  
Primary Reference

Abstract Background Hepcidin concentrations measured by various methods differ considerably, complicating interpretation. Here, a previously identified plasma-based candidate secondary reference material (csRM) was modified into a serum-based two-leveled sRM. We validated its functionality to increase the equivalence between methods for international standardization. Methods We applied technical procedures developed by the International Consortium for Harmonization of Clinical Laboratory Results. The sRM, consisting of lyophilized serum with cryolyoprotectant, appeared commutable among nine different measurement procedures using 16 native human serum samples in a first round robin (RR1). Harmonization potential of the sRM was simulated in RR1 and evaluated in practice in RR2 among 11 measurement procedures using three native human plasma samples. Comprehensive purity analysis of a candidate primary RM (cpRM) was performed by state of the art procedures. The sRM was value assigned with an isotope dilution mass spectrometry-based candidate reference method calibrated using the certified pRM. Results The inter-assay CV without harmonization was 42.1% and 52.8% in RR1 and RR2, respectively. In RR1, simulation of harmonization with sRM resulted in an inter-assay CV of 11.0%, whereas in RR2 calibration with the material resulted in an inter-assay CV of 19.1%. Both the sRM and pRM passed international homogeneity criteria and showed long-term stability. We assigned values to the low (0.95±0.11 nmol/L) and middle concentration (3.75±0.17 nmol/L) calibrators of the sRM. Conclusions Standardization of hepcidin is possible with our sRM, which value is assigned by a pRM. We propose the implementation of this material as an international calibrator for hepcidin.

scholarly journals Optimization of Aflatoxin B1 Aptasensing

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Marzieh Jafari ◽  
Mohsen Rezaei ◽  
Heibatullah Kalantari ◽  
Maryam Tabarzad ◽  
Bahram Daraei
Keyword(s):  
Horseradish Peroxidase ◽  
Binding Affinity ◽  
Aflatoxin B1 ◽  
Low Cost ◽  
Term Stability ◽  
Long Term Stability ◽  
Conventional Methods ◽  
User Friendly ◽  
Hrp Horseradish Peroxidase

Combination of aptamers with DNAzymes attracted intense attention for development of DNA-based biosensors for detection of mycotoxins. In the present study a combination of aflatoxin B1 specific aptamer and HRP- (horseradish peroxidase-) mimicking DNAzyme was optimized for detecting aflatoxin B1. Detecting approach is based on the binding affinity of aflatoxin B1 to its specific aptamer and conversion of substrate to a detectable colorimetric signal by a linked DNAzyme. Compared to conventional methods for aflatoxin B1 detection, DNA-based assay has the advantages of low cost, long-term stability, and rapid, simple, and user-friendly steps.

scholarly journals Maternally and Naturally Acquired Antibodies to Shiga Toxins in a Cohort of Calves Shedding Shiga-Toxigenic Escherichia coli

2009 ◽  
Vol 75 (11) ◽  
pp. 3695-3704 ◽  
Author(s):  
Julia Fröhlich ◽  
Georg Baljer ◽  
Christian Menge
Keyword(s):  
Escherichia Coli ◽  
Calf Serum ◽  
Positive Culture ◽  
Neutralization Assay ◽  
Serum Samples ◽  
Shiga Toxins ◽  
Specific Antibodies ◽  
Time Of Infection ◽  
Newborn Calves

ABSTRACT Calves become infected with Shiga toxin-producing Escherichia coli (STEC) early in life, which frequently results in long-term shedding of the zoonotic pathogen. Little is known about the animals' immunological status at the time of infection. We assessed the quantity and dynamics of maternal and acquired antibodies to Shiga toxins (Stx1 and Stx2), the principal STEC virulence factors, in a cohort of 27 calves. Fecal and serum samples were taken repeatedly from birth until the 24th week of age. Sera, milk, and colostrums of dams were also assessed. STEC shedding was confirmed by detection of stx in fecal cultures. Stx1- and Stx2-specific antibodies were quantified by Vero cell neutralization assay and further analyzed by immunoblotting. By the eighth week of age, 13 and 15 calves had at least one stx 1-type and at least one stx 2-type positive culture, respectively. Eleven calves had first positive cultures only past that age. Sera and colostrums of all dams and postcolostral sera of all newborn calves contained Stx1-specific antibodies. Calf serum titers decreased rapidly within the first 6 weeks of age. Only five calves showed Stx1-specific seroconversion. Maternal and acquired Stx1-specific antibodies were mainly directed against the StxA1 subunit. Sparse Stx2-specific titers were detectable in sera and colostrums of three dams and in postcolostral sera of their calves. None of the calves developed Stx2-specific seroconversion. The results indicate that under natural conditions of exposure, first STEC infections frequently coincide with an absence of maternal and acquired Stx-specific antibodies in the animals' sera.

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