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.

scholarly journals Demonstration of a Label-Free and Low-Cost Optical Cavity-Based Biosensor Using Streptavidin and C-Reactive Protein

Biosensors ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 4
Author(s):  
Donggee Rho ◽  
Seunghyun Kim
Keyword(s):  
Limit Of Detection ◽  
Point Of Care ◽  
Low Cost ◽  
Optical Cavity ◽  
Sample Volume ◽  
Small Sample ◽  
Label Free ◽  
C Reactive Protein ◽  
Reactive Protein ◽  
Cavity Structure

An optical cavity-based biosensor (OCB) has been developed for point-of-care (POC) applications. This label-free biosensor employs low-cost components and simple fabrication processes to lower the overall cost while achieving high sensitivity using a differential detection method. To experimentally demonstrate its limit of detection (LOD), we conducted biosensing experiments with streptavidin and C-reactive protein (CRP). The optical cavity structure was optimized further for better sensitivity and easier fluid control. We utilized the polymer swelling property to fine-tune the optical cavity width, which significantly improved the success rate to produce measurable samples. Four different concentrations of streptavidin were tested in triplicate, and the LOD of the OCB was determined to be 1.35 nM. The OCB also successfully detected three different concentrations of human CRP using biotinylated CRP antibody. The LOD for CRP detection was 377 pM. All measurements were done using a small sample volume of 15 µL within 30 min. By reducing the sensing area, improving the functionalization and passivation processes, and increasing the sample volume, the LOD of the OCB are estimated to be reduced further to the femto-molar range. Overall, the demonstrated capability of the OCB in the present work shows great potential to be used as a promising POC biosensor.

scholarly journals Direct-RT-qPCR Detection of SARS-CoV-2 without RNA Extraction as Part of a COVID-19 Testing Strategy: From Sample to Result in One Hour

Diagnostics ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 605 ◽  
Author(s):  
Eva Kriegova ◽  
Regina Fillerova ◽  
Petr Kvapil
Keyword(s):  
High Throughput Screening ◽  
High Speed ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Rna Extraction ◽  
Rna Isolation ◽  
High Sensitivity ◽  
Ease Of Use ◽  
Diagnostic Tools ◽  
Heat Inactivation

Due to the lack of protective immunity in the general population and the absence of effective antivirals and vaccines, the Coronavirus disease 2019 (COVID-19) pandemic continues in some countries, with local epicentres emerging in others. Due to the great demand for effective COVID-19 testing programmes to control the spread of the disease, we have suggested such a testing programme that includes a rapid RT-qPCR approach without RNA extraction. The Direct-One-Step-RT-qPCR (DIOS-RT-qPCR) assay detects severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in less than one hour while maintaining the high sensitivity and specificity required of diagnostic tools. This optimised protocol allows for the direct use of swab transfer media (14 μL) without the need for RNA extraction, achieving comparable sensitivity to the standard method that requires the time-consuming and costly step of RNA isolation. The limit of detection for DIOS-RT-qPCR was lower than seven copies/reaction, which translates to 550 virus copies/mL of swab. The speed, ease of use and low price of this assay make it suitable for high-throughput screening programmes. The use of fast enzymes allows RT-qPCR to be performed under standard laboratory conditions within one hour, making it a potential point-of-care solution on high-speed cycling instruments. This protocol also implements the heat inactivation of SARS-CoV-2 (75 °C for 10 min), which renders samples non-infectious, enabling testing in BSL-2 facilities. Moreover, we discuss the critical steps involved in developing tests for the rapid detection of COVID-19. Implementing rapid, easy, cost-effective methods can help control the worldwide spread of the COVID-19 infection.

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 Multiplex Detection of Three Select Agents Directly from Blood by Use of the GeneXpert System

2019 ◽  
Vol 57 (5) ◽  
Author(s):  
Padmapriya P. Banada ◽  
Srinidhi Deshpande ◽  
Sukalyani Banik ◽  
Darshini Shah ◽  
Ranie Koshy ◽  
...  
Keyword(s):  
Rapid Detection ◽  
Dynamic Range ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Severe Disease ◽  
High Sensitivity ◽  
Negative Control ◽  
Blood Samples ◽  
Content Type ◽  
Clinical Patient

ABSTRACT Francisella tularensis, Bacillus anthracis, and Yersinia pestis are tier 1 select agents with the potential to rapidly cause severe disease. Rapid detection of these bacteria from patient samples at the point of care could contribute to improved clinical outcomes in the event of a bioterrorism attack. A multiplex nested PCR assay for detection of F. tularensis, B. anthracis, and Y. pestis directly from patient blood samples was developed using the GeneXpert system. The multiplex GeneXpert cartridge-based assay includes all necessary sample processing and amplification reagents. Blood samples spiked with different numbers of CFU were used to measure the analytical limit of detection (LOD) and dynamic range. Sensitivity was determined by testing spiked blood samples and negative-control blood in a blind manner. Specificity was determined by testing against nontarget pathogens and blood samples from clinical patients. The assay LOD was 8.5 CFU/ml for F. tularensis, 10 CFU/ml for B. anthracis, and 4.5 CFU/ml for Y. pestis. The sensitivity was 100% at the LOD for all three select agent bacteria in spiked patient blood samples. The assay specificity was 100% when it was tested against both nontarget pathogens and clinical patient blood samples. The total assay time was approximately 100 min. This automated assay, which is suitable for use at the point of care, identifies three select agents directly in blood without the need for enrichment with a high sensitivity within 100 min. This assay may enable rapid detection and treatment of patients infected with the target organisms in the event of a bioterrorism attack.

scholarly journals Recent Advances of Field-Effect Transistor Technology for Infectious Diseases

Biosensors ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 103
Author(s):  
Abbas Panahi ◽  
Deniz Sadighbayan ◽  
Saghi Forouhi ◽  
Ebrahim Ghafar-Zadeh
Keyword(s):  
Infectious Diseases ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Limit Of Detection ◽  
Point Of Care ◽  
High Sensitivity ◽  
Cmos Technology ◽  
Oxide Semiconductor ◽  
Label Free ◽  
Effect Transistor

Field-effect transistor (FET) biosensors have been intensively researched toward label-free biomolecule sensing for different disease screening applications. High sensitivity, incredible miniaturization capability, promising extremely low minimum limit of detection (LoD) at the molecular level, integration with complementary metal oxide semiconductor (CMOS) technology and last but not least label-free operation were amongst the predominant motives for highlighting these sensors in the biosensor community. Although there are various diseases targeted by FET sensors for detection, infectious diseases are still the most demanding sector that needs higher precision in detection and integration for the realization of the diagnosis at the point of care (PoC). The COVID-19 pandemic, nevertheless, was an example of the escalated situation in terms of worldwide desperate need for fast, specific and reliable home test PoC devices for the timely screening of huge numbers of people to restrict the disease from further spread. This need spawned a wave of innovative approaches for early detection of COVID-19 antibodies in human swab or blood amongst which the FET biosensing gained much more attention due to their extraordinary LoD down to femtomolar (fM) with the comparatively faster response time. As the FET sensors are promising novel PoC devices with application in early diagnosis of various diseases and especially infectious diseases, in this research, we have reviewed the recent progress on developing FET sensors for infectious diseases diagnosis accompanied with a thorough discussion on the structure of Chem/BioFET sensors and the readout circuitry for output signal processing. This approach would help engineers and biologists to gain enough knowledge to initiate their design for accelerated innovations in response to the need for more efficient management of infectious diseases like COVID-19.

Determination of sex-specific 99th percentile upper reference limits for a point of care high sensitivity cardiac troponin I assay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Fred S. Apple ◽  
Karen Schulz ◽  
Christian W. Schmidt ◽  
Trees S. Y. van Domburg ◽  
Judith M. Fonville ◽  
...  
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Limit Of Detection ◽  
Point Of Care ◽  
High Sensitivity ◽  
The Novel ◽  
Limit Of Quantitation ◽  
Reference Limits ◽  
Males And Females

Abstract Objectives High sensitivity (hs) cardiac troponin (cTn) assays are defined per the IFCC Committee on Clinical Application of Cardiac Biomarker (C-CB) by the ability to measure ≥ 50% of concentrations greater than the limit of detection (LoD) with an impression of ≤10% at sex-specific 99th percentiles. Our study determined the sex-specific 99th percentile upper reference limits for males and females utilizing heparinized plasma from AACC universal sample bank for the Siemens point of care (POC) Atellica® VTLi hs-cTnI immunoassay. Methods Apparently healthy subjects, included overall 693, males 363, and females 330, following exclusionary surrogate biomarker use of hemoglobin A1c, NT-proBNP, and eGFR, along with statin medication. hs-cTnI was measured in a central laboratory, on multiple POC Atellica® VTLi immunoassay analyzers. The LoD was 1.24 ng/L and limit of quantitation (CV 20%) was 6.7 ng/L. 99th percentile URLs were determined by the nonparametric (NP) method. Results Histograms of the hs-cTnI concentrations (ng/L) for males and females were used to visualize the distributions and concentrations in men and women and differed significantly (pre- and post-exclusion, both p <0.001). 99th percentile URLs were: overall 23 ng/L (90% CI 20–32 ng/L); male 27 ng/L (CI 21–37 ng/L); female 18 ng/L (CI 9–78 ng/L). The percentages of subjects having a measurable concentration ≥ the LoD were: overall 83.7%, male 87.3%, female 79.7%. Conclusions Our findings show the novel POC Atellica® VTLi hs-cTnI assay meets the designation of a ‘high-sensitivity’ assay using heparinized plasma.

Organotrialkoxysilane-mediated synthesis of functional noble metal nanoparticles and their bimetallic for electrochemical recognition of L-tryptophan

MRS Advances ◽  
2020 ◽  
Vol 5 (46-47) ◽  
pp. 2429-2444
Author(s):  
P.C. Pandey ◽  
Shubhangi Shukla ◽  
Govind Pandey ◽  
Roger J. Narayan
Keyword(s):  
Modified Electrode ◽  
Noble Metal ◽  
Limit Of Detection ◽  
High Sensitivity ◽  
Differential Pulse ◽  
Noble Metal Nanoparticles ◽  
Core Shell ◽  
Oxidation Potentials ◽  
Wide Range ◽  
Sequential Reduction

AbstractEffective and pH-sensitive electrochemical monitoring of L-tryptophan using noble metal nanocatalysts was evaluated in this study. This work examined the electrocatalytic influence of nanoparticles on the oxidation of amino acids with the variation of pH in working media. Bimetallic nanohybrids of palladium, silver, and gold (e.g., Pd/Ag and Pd/Au nanoparticles) were processed using organofunctionalized alkoxysilanes (3-aminopropyltrimethoxysilane (3-APTMS) and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (EETMOS)) via a sequential reduction pathway. Transmission electron microscopy (TEM) demonstrated the role of the alkoxysilanes in determining the size of the nanoparticles and the distribution of metals in the core-shell configuration. The cluster-like morphology of PdNPs was remodeled to form bimetallic nanomaterials (Pd-AuNPs and Pd-AgNPs) with a core-shell structure. Enhancement in the electrooxidation behavior was shown to depend on the nanomaterial and the pH of the medium. The Pd-AgNPs modified electrode exhibited high sensitivity and selectivity, with characteristic amplification in cathodic peak current at lower oxidation potentials (0.659 V, 0.782 V, and 0.890 V at pH values 4, 7, and 9, respectively) due to its greater stability. Differential pulse voltammetric (DPV) scans were recorded over a wide range of concentrations from 0.1 μM to 1000μM; the Pd-AgNPs modified electrode showed the lowest limit of detection of 0.1μM at pH 4, 0.5 μM at pH 7, and 0.5 μM at pH 9.

Validation of a new assay for α-synuclein detection in cerebrospinal fluid

2017 ◽  
Vol 55 (2) ◽  
Author(s):  
Marthe Gurine Førland ◽  
Annika Öhrfelt ◽  
Linn Silje Oftedal ◽  
Ole-Bjørn Tysnes ◽  
Jan Petter Larsen ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Neurodegenerative Diseases ◽  
Dementia With Lewy Bodies ◽  
Limit Of Detection ◽  
Lewy Bodies ◽  
High Sensitivity ◽  
Cross Reactivity ◽  
Additional Method ◽  
Potential Biomarker ◽  
Assay Protocol

AbstractBackground:Abnormal α-synuclein aggregation and deposition is the pathological hallmark of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB), but is also found in Alzheimer disease (AD). Therefore, there is a gaining interest in α-synuclein in cerebrospinal fluid (CSF) as potential biomarker for these neurodegenerative diseases. To broaden the available choices of α-synuclein measurement in CSF, we developed and validated a new assay for detecting total α-synuclein.Methods:This novel ELISA uses commercially available antibodies and is based on electrochemiluminescence technology. The assay protocol is straightforward, with short and simple incubation steps, and requires only small amounts of CSF. We validated this assay for precision, parallelism, dilution linearity, specificity, and spike recovery. We further compared it to the newly validated α-synuclein assay from BioLegend by analyzing a set of 50 CSF samples with both assays.Results:The new assay quantifies α-synuclein in CSF with a lower limit of detection of 36.3 pg/mL and shows no cross-reactivity with human β- and γ-synuclein. Results of dilution linearity, parallelism, spike recovery, and precision classify this assay as well suited for α-synuclein detection in human CSF samples.Conclusions:We present a novel assay based on freely available components to quantify total α-synuclein in CSF as an additional method for α-synuclein as a biomarker in neurodegenerative diseases. The assay convinces with its simple and convenient protocol paired with high sensitivity.

Sensitive method for analysis of strontium in human and animal plasma by graphite furnace atomic absorption spectrophotometry

1995 ◽  
Vol 41 (8) ◽  
pp. 1159-1163 ◽  
Author(s):  
R Barto ◽  
A J Sips ◽  
W J van der Vijgh ◽  
J C Netelenbos
Keyword(s):  
Atomic Absorption ◽  
Limit Of Detection ◽  
Graphite Furnace ◽  
High Sensitivity ◽  
Atomic Absorption Spectrophotometry ◽  
Small Sample ◽  
Pharmacokinetic Studies ◽  
Limit Of Quantification ◽  
Absorption Spectrophotometry ◽  
Graphite Furnace Atomic Absorption

Abstract For long-term pharmacokinetic studies in humans as well as in experimental animals, an analysis of strontium (Sr) with a low detection limit and high sensitivity is necessary. The data presented here describe the optimization of the furnace program and sample handling for measuring Sr in plasma by using graphite furnace atomic absorption spectrophotometry. The method was validated and applied to studies on the pharmacokinetics of SrCl2 in humans and rats. Calibration curves were linear up to 57.1 nmol/L. The limit of detection and lower limit of quantification were 0.21 and 0.57 nmol/L, respectively. Reciprocal sensitivity was 0.53 nmol/L Sr at A = 0.0044. The intraassay precision was 2.2%, 1.5%, and 1.1% (n = 6) at 4.57, 22.7, and 49.2 nmol/L Sr, respectively. At these concentrations, the interassay precision and recovery were 0.7%, 1.5%, and 1.8% and 100.4%, 99.1%, and 100.6% (n = 12), respectively. The endogenous Sr concentration in human plasma samples was 0.27 +/- 0.07 mumol/L (n = 18). Pharmacokinetic studies in a human volunteer and in rats demonstrated that this procedure was suited for measuring low Sr concentrations and was applicable to small sample volumes.

Giant Magnetoresistive Based Handheld System for Rapid Detection of Human NT-proBNP

2019 ◽  
Author(s):  
Wei Wang ◽  
Todd Klein ◽  
James Collins
Keyword(s):  
Limit Of Detection ◽  
Detection System ◽  
Point Of Care ◽  
High Sensitivity ◽  
Time Signal ◽  
Point Of Care Testing ◽  
Detection Range ◽  
Further Development ◽  
Signal Readout

In this work, we developed giant magnetoresistive (GMR) based handheld biosensing systems that serve as platform for detecting human NT-proBNP. This assay takes advantages of high sensitivity and real-time signal readout of GMR biosensor. The limit of detection was estimated to be less than 0.01ng/mL, and detection range covered from 0.01 ng/mL to 5 ng/mL was obtained. The assay can be completed within 20 min, which is very important for further development of point-of-care testing. The proposed GMR handheld system is also successfully used for the detection of real NT-proBNP human samples. It can be foreseen that this handheld detection system could become a robust contender in the applications of in vitro biomarker diagnostics.

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