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Kim HR, Kim S, Jung J, Lee H, Ho K, Kim B, Oh S. Enhancing LOD determination in gas chromatography: Validating the Hubaux-Vos method for gas concentration measurement. J Chromatogr A 2024; 1720:464764. [PMID: 38458137 DOI: 10.1016/j.chroma.2024.464764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 01/23/2024] [Accepted: 02/19/2024] [Indexed: 03/10/2024]
Abstract
The limit of detection (LOD) is a crucial measure in analytical methods, representing the smallest amount of a substance that can be distinguished from background noise. In the realm of gas chromatography (GC), however, determining LOD can be quite subjective, leading to significant variability among researchers. In this study, we validate the Hubaux-Vos method, an International Standards Organization(ISO)-approved approach for determining LOD in gas concentration measurements, using a GC equipped with a discharge ionization detector (DID) and a dynamic dilution system. We employ a gas mixture certified reference material (CRM) of CO, CH4, and CO2 at various concentrations to generate calibration curves for each gas. Subsequently, we estimate the LODs for each gas using the Hubaux-Vos method. Surprisingly, our findings indicate a notable difference between the LODs calculated using the Hubaux-Vos method and those confirmed through experiments. This highlights the importance of critically examining the theoretical foundations of LOD determination. We strongly recommend researchers to scrutinize the principles guiding LOD determination. The method proposed in this study offers an effective way to rigorously validate theoretical approaches for estimating LODs in gas concentration measurements using GC.
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Affiliation(s)
- Hyeong Rae Kim
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea
| | - Sunwoo Kim
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea
| | - Jinsang Jung
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea
| | - Hwan Lee
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea
| | - Keon Ho
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea
| | - Byeongmoon Kim
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea
| | - Sanghyub Oh
- Gas Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon, 34113, South Korea.
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2
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Singh M, Kumar J. Flourescence sensors for heavy metal detection: major contaminants in soil and water bodies. ANAL SCI 2023; 39:1829-1838. [PMID: 37531068 DOI: 10.1007/s44211-023-00392-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 06/28/2023] [Indexed: 08/03/2023]
Abstract
Due to the increasing consumption of heavy metals, there is a rising need for specific and useful methods that are employed for the detection of heavy metals. Fluorescence sensing is a highly selective, rapid and biosensing technique that is employed in the determination of some heavy metals in any sample of soil or water, any other living person, the food being consumed or any other substance which are being used daily. These fluorescent methods are a type of analytical technique and they are mainly based on detection. Many types of metal conjugated molecules have been used of the detection of these heavy metals with various mechanisms. We have taken into account some specific sensor molecules as they were more suitable and easily accessible. These techniques that were employed in the detection of various heavy metals such as copper, lead and mercury have been discussed in the following review article.
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Affiliation(s)
- M Singh
- Chandigarh University, Mohali, Punjab, 140413, India
| | - J Kumar
- Chandigarh University, Mohali, Punjab, 140413, India.
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Nguyen T, Vinayaka AC, Huynh VN, Linh QT, Andreasen SZ, Golabi M, Bang DD, Møller JK, Wolff A. PATHPOD - A loop-mediated isothermal amplification (LAMP)-based point-of-care system for rapid clinical detection of SARS-CoV-2 in hospitals in Denmark. Sens Actuators B Chem 2023; 392:134085. [PMID: 37304211 PMCID: PMC10245468 DOI: 10.1016/j.snb.2023.134085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 05/19/2023] [Accepted: 06/03/2023] [Indexed: 06/13/2023]
Abstract
Sensitive and rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a vital goal in the ongoing COVID-19 pandemic. We present in this comprehensive work, for the first time, detailed fabrication and clinical validation of a point of care (PoC) device for rapid, onsite detection of SARS-CoV-2 using a real-time reverse-transcription loop-mediated isothermal amplification (RT-LAMP) reaction on a polymer cartridge. The PoC system, namely PATHPOD, consisting of a standalone device (weight less than 1.2 kg) and a cartridge, can perform the detection of 10 different samples and two controls in less than 50 min, which is much more rapid than the golden standard real-time reverse-transcription Polymerase Chain Reaction (RT-PCR), typically taking 16-48 h. The novel total internal reflection (TIR) scheme and the reactions inside the cartridge in the PoC device allow monitoring of the diagnostic results in real-time and onsite. The analytical sensitivity and specificity of the PoC test are comparable with the current RT-PCR, with a limit of detection (LOD) down to 30-50 viral genome copies. The robustness of the PATHPOD PoC system has been confirmed by analyzing 398 clinical samples initially examined in two hospitals in Denmark. The clinical sensitivity and specificity of these tests are discussed.
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Affiliation(s)
- Trieu Nguyen
- BioLabChip Group, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Aaydha Chidambara Vinayaka
- Laboratory of Applied Micro and Nanotechnology (LAMINATE), Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Van Ngoc Huynh
- BioLabChip Group, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Quyen Than Linh
- BioLabChip Group, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Sune Zoëga Andreasen
- BioLabChip Group, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Mohsen Golabi
- Laboratory of Applied Micro and Nanotechnology (LAMINATE), Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Dang Duong Bang
- Laboratory of Applied Micro and Nanotechnology (LAMINATE), Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Jens Kjølseth Møller
- Department of Clinical Microbiology, University Hospital of Southern Denmark, Vejle Hospital, Beriderbakken 4, DK-7100 Vejle, Denmark
| | - Anders Wolff
- BioLabChip Group, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
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Abstract
Enzyme-linked immunosorbent assay (ELISA) is by definition a biosensor. However, not all immuno-biosensors involve the use of enzymes, while other biosensors incorporate ELISA as a key signaling component. In this chapter, we review the role of ELISA in signal amplification, integration with microfluidic systems, digital labeling, and electrochemical detection.
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Gegenschatz SA, Chiappini FA, Teglia CM, Muñoz de la Peña A, Goicoechea HC. Binding the gap between experiments, statistics, and method comparison: A tutorial for computing limits of detection and quantification in univariate calibration for complex samples. Anal Chim Acta 2022; 1209:339342. [PMID: 35569842 DOI: 10.1016/j.aca.2021.339342] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 11/30/2022]
Abstract
The present tutorial aims to review the most frequently reported criteria for the calculation of the limits of detection (LOD) and quantification (LOQ) in univariate calibration, summarizing their fundamentals, advantages, and limitations. The current criteria for estimating LOD and LOQ are based on diverse theoretical and/or empirical assumptions and require different amounts of experimental data, making the calculation rather complex in some cases. Moreover, alternative forms for calculating LOD/LOQ frequently lead to dissimilar results. This scenario might worsen in the case of complex analytical systems. Throughout this tutorial, different forms of calculating LOD/LOQ are illustrated using previously reported experimental datasets in the environmental chemistry field as examples. The influence of the sample matrix during the estimation of LOD/LOQ parameters is investigated through one calibration approache. The discrepancies in the obtained results with different criteria for the calculation of LOD/LOQ are highlighted. Finally, general guidelines and recommendations regarding experimental and data processing issues are proposed, aiming to promote fair criteria for the comparison of different analytical methodologies in terms of prediction ability and detection capability.
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Affiliation(s)
- Sofía A Gegenschatz
- Laboratorio de Desarrollo Analítico y Quimiometría (LADAQ), Cátedra de Química Analítica I, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, 3000, Santa Fe, Argentina
| | - Fabricio A Chiappini
- Laboratorio de Desarrollo Analítico y Quimiometría (LADAQ), Cátedra de Química Analítica I, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, 3000, Santa Fe, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290 CP, C1425FQB, Buenos Aires, Argentina
| | - Carla M Teglia
- Laboratorio de Desarrollo Analítico y Quimiometría (LADAQ), Cátedra de Química Analítica I, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, 3000, Santa Fe, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290 CP, C1425FQB, Buenos Aires, Argentina.
| | | | - Héctor C Goicoechea
- Laboratorio de Desarrollo Analítico y Quimiometría (LADAQ), Cátedra de Química Analítica I, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, 3000, Santa Fe, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290 CP, C1425FQB, Buenos Aires, Argentina.
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Jurašeková Z, Jutková A, Kožár T, Staničová J. Vibrational characterization of the pesticide molecule Tebuconazole. Spectrochim Acta A Mol Biomol Spectrosc 2022; 268:120629. [PMID: 34824006 DOI: 10.1016/j.saa.2021.120629] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 11/01/2021] [Accepted: 11/11/2021] [Indexed: 06/13/2023]
Abstract
Pesticide use worldwide exhibits a positive effect on agricultural production while it may negatively affect organisms living in soil, water or the air. Importantly, numerous negative health effects also occur in humans exposed to (accumulated) pesticides or their metabolites over a long period of time. To prevent both environmental catastrophes and adverse human health impacts, initial studies of the selected pesticides need to be performed together with the constant post-approval control; risk assessment analysis and on site monitoring have to be continuously carried out. Given this, Raman spectroscopy, especially surface-enhanced Raman spectroscopy (SERS), during the last decade has become a powerful analytical technique since it can offer quick, selective, and in situ detection of selected pollutants found in analyzed samples at very low concentrations. Moreover, the structural changes caused by the pollutant-biomacromolecule interaction can also be recognized in the molecule-specific Raman spectral signatures of biomolecules. In this study, we report a vibrational characterization of the fungicide molecule Tebuconazole (TB) which is listed to be a possible carcinogen. Even though its international and common use there is no evidence about the use of Raman/SERS spectroscopy to detect it sensitively and selectively as well as to analyse its impacts on biological systems. Therefore, we have recorded and calculated Raman and infrared spectra of TB. Furthermore, SERS spectra of TB were also registered and comprehensively analysed in view of the employed SERS substrates, dependence on the excitation wavelengths and pH of the analysed molecular systems. The molecule of TB interacts preferentially through the triazole moiety with the colloidal metal nanoparticles (NPs) whereas the silver NPs prepared by reduction of silver nitrate with hydroxylamine hydrochloride resulted to be the most effective ones. Consequently, the limit of detection was determined to be 1.4 μM≈430 ppb. The present paper thus could serve significantly for further investigations focused on both conducting vibrational analyses of structurally related molecules as well as providing a more precise explanation of the mechanism of action of TB and its influence on biological macromolecules.
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Affiliation(s)
- Zuzana Jurašeková
- Department of Biophysics, Faculty of Sciences, University of P. J. Šafárik, Jesenná 5, 040 01 Košice, Slovakia.
| | - Annamária Jutková
- Department of Biology and Physiology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovakia
| | - Tibor Kožár
- Center for Interdisciplinary Biosciences, TIP-UPJŠ, Jesenná 5, 040 01 Košice, Slovakia
| | - Jana Staničová
- Department of Chemistry, Biochemistry and Biophysics, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovakia; Institute of Biophysics and Informatics, First Faculty of Medicine, Charles University, Kateřinská 1, Prague, Czech Republic.
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Singh MK, Pal S, Verma A, Das R, Prajapati YK. A nanolayered structure for sensitive detection of hemoglobin concentration using surface plasmon resonance. Appl Phys A Mater Sci Process 2021; 127:832. [PMID: 34658541 PMCID: PMC8511850 DOI: 10.1007/s00339-021-04985-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 10/03/2021] [Indexed: 06/13/2023]
Abstract
The objective of the proposed work is to design a biosensor that monitors hemoglobin (Hb) concentration using the combination of nanolayer, i.e., barium titanate (BaTiO3) and antimonene based on surface plasmon resonance (SPR) technique. Antimonene is used here as bio-recognition element (BRE) layer to attach the Hb analyte through physical adsorption due to its hydrophilic nature, higher adsorption energy and larger active surface area. The use of BaTiO3 adlayer (7 nm) just before antimonene is to enhance the refractive index (RI) sensitivity up to 1.90 times for the proposed SPR biosensor. The reason behind sensitivity enhancement is its high dielectric constant which enhances the electromagnetic field with in analyte medium. The performance of the biosensor is demonstrated with performance parameters namely sensitivity, detection accuracy (DA), figure of merit (FOM) and resolution. The proposed biosensor has potential to achieve much higher performance in terms of RI sensitivity of 303.83°/RIU, FOM of 50.39 RIU-1 and resolution of 0.021 g/l in comparison with reported biosensors in the literature for detection of Hb concentration. Thus, based on the obtained results one can say that the proposed work unlocks a reliable sensing in the field of medical science to detect hemoglobin-related diseases in human being.
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Affiliation(s)
- Maneesh Kumar Singh
- Department of Electronics Engineering, National Institute of Technology Uttarakhand, Srinagar, Pauri Garhwal, Uttarakhand 246174 India
| | - Sarika Pal
- Department of Electronics Engineering, National Institute of Technology Uttarakhand, Srinagar, Pauri Garhwal, Uttarakhand 246174 India
| | - Alka Verma
- Department of Electronics and Communication Engineering, Institute of Engineering and Rural Technology Allahabad, Prayagraj, Uttar Pradesh 211002 India
| | - Ritwick Das
- School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar, 752050 India
| | - Yogendra Kumar Prajapati
- Department of Electronics and Communication Engineering, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, Uttar Pradesh 211004 India
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Kontogianni K, Cubas-Atienzar AI, Wooding D, Buist K, Thompson CR, Williams CT, Baldwin L, Escadafal C, Sacks JA, Adams ER, Edwards T. Lateral flow antigen tests can sensitively detect live cultured virus of the SARS-CoV-2 B1.1.7 lineage. J Infect 2021; 83:e1-e4. [PMID: 34062185 PMCID: PMC8164512 DOI: 10.1016/j.jinf.2021.05.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 05/24/2021] [Accepted: 05/26/2021] [Indexed: 01/26/2023]
Affiliation(s)
- Konstantina Kontogianni
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Ana I Cubas-Atienzar
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Dominic Wooding
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Kate Buist
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Caitlin R Thompson
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Christopher T Williams
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Lisa Baldwin
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Camille Escadafal
- FIND, Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | - Jilian A Sacks
- FIND, Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | - Emily R Adams
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K
| | - Thomas Edwards
- Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, U.K.
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Jaiswal A, Kumar A, Prakash R. Facile synthesis of doped C xN y QDs as photoluminescent matrix for direct detection of hydroquinone. Spectrochim Acta A Mol Biomol Spectrosc 2021; 246:119019. [PMID: 33068899 DOI: 10.1016/j.saa.2020.119019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/21/2020] [Accepted: 09/26/2020] [Indexed: 06/11/2023]
Abstract
In this work, we are reporting facile hydrothermal synthesis of a highly photoluminescent doped carbon nitride quantum dots (CxNyQDs) and implied it for direct detection of hydroquinone (H2Q) by photoluminescence quenching phenomenon. Oxygen and sulphur moieties are regarded as dopant species in CxNyQDs and sourced from cheap solid precursors viz. cysteine and maleic acid. Morphological studies of CxNyQDs have done by SEM and TEM techniques, while structural analysis has carried out using FTIR, XPS, EDS and UV-Visible spectroscopy. The strong tendency of dispersivity of this QD in water has revealed by its zeta potential value of -32.4 mV. Optical properties of the as-prepared QDs have optimized at different excitation wavelengths. The photoluminescence stability of the dispersion is tested in various pH solutions and under continuous UV irradiation (365 nm). After that, sensing property is observed in quenching of photoluminescence feature of as-prepared QDs by direct addition of various concentrations of H2Q. We obtained lower detection limit (LOD) of 50 nM (S/N = 3) in linear range from 12 to 57.5 μM. The reduction in photoluminescence of QDs may be attributed to electron transfer from QDs to oxidized H2Q via -S- and -COO- groups present at its surface. Further, as-prepared QDs matrix exhibited high selectivity for hydroquinone over a range of potential interfering agents. Thus, the present work shows cost-effective facile synthesis of highly stable O- and S-doped carbon nitride (CxNy) quantum dots as promising photoluminescent sensor for pollutant hydroquinone without help of any enzyme or polymer assisted system.
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Affiliation(s)
- Aniruddha Jaiswal
- School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India
| | - Ashish Kumar
- School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India
| | - Rajiv Prakash
- School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India.
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Del Pilar Martinez Viedma M, Puri V, Oldfield LM, Shabman RS, Tan GS, Pickett BE. Optimization of qRT-PCR assay for zika virus detection in human serum and urine. Virus Res 2019; 263:173-8. [PMID: 30742853 DOI: 10.1016/j.virusres.2019.01.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 01/11/2019] [Accepted: 01/21/2019] [Indexed: 12/31/2022]
Abstract
Zika Virus (ZIKV) is a mosquito-borne flavivirus that the World Health Organization (WHO) declared a global concern due to the severity of infection. This study focuses on determining the level of detection of ZIKV RNA in human serum and urine. Known amounts of Zika virus were added to uninfected human serum and urine samples. Different reverse transcriptases were compared to select the optimal enzyme for this application. Zika RNA in these samples was then quantified with qRT-PCR to determine the lower limit of detection in these fluids and to construct a standard curve. Student's t-test of paired samples was used in order to identify statistical differences. The SuperScript III enzyme was able to produce more ZIKV cDNA when compared to PrimeScript. Zika virus RNA was found to be detectable at lower levels (2.5 PFU/mL) in urine than in serum (250 PFU/mL) when using SuperScript III. This study demonstrates how the selection of both the human clinical specimen, and the reverse transcriptase enzyme involved in the molecular detection of ZIKV by quantitative real-time polymerase chain reaction (qRT-PCR), play an important role in enabling improved detection of the virus.
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Ordoñez JA, Bandyopadhyay D, Lachos VH, Cabral CRB. Geostatistical estimation and prediction for censored responses. Spat Stat 2018; 23:109-123. [PMID: 29577023 PMCID: PMC5860689 DOI: 10.1016/j.spasta.2017.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Spatially-referenced geostatistical responses that are collected in environmental sciences research are often subject to detection limits, where the measures are not fully quantifiable. This leads to censoring (left, right, interval, etc), and various ad hoc statistical methods (such as choosing arbitrary detection limits, or data augmentation) are routinely employed during subsequent statistical analysis for inference and prediction. However, inference may be imprecise and sensitive to the assumptions and approximations involved in those arbitrary choices. To circumvent this, we propose an exact maximum likelihood estimation framework of the fixed effects and variance components and related prediction via a novel application of the Stochastic Approximation of the Expectation Maximization (SAEM) algorithm, allowing for easy and elegant estimation of model parameters under censoring. Both simulation studies and application to a real dataset on arsenic concentration collected by the Michigan Department of Environmental Quality demonstrate the advantages of our method over the available naïve techniques in terms of finite sample properties of the estimates, prediction, and robustness. The proposed methods can be implemented using the R package CensSpatial.
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Affiliation(s)
- José A. Ordoñez
- Department of Statistics, Campinas State University, Campinas, São Paulo, Brazil
| | | | - Victor H. Lachos
- Department of Statistics, University of Connecticut, Storrs, CT 06269, U.S.A
| | - Celso R. B. Cabral
- Department of Statistics, Federal University of Amazonas, Manaus, Brazil
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Li B, Liu H, Wang W. Multiplex real-time PCR assay for detection of Escherichia coli O157:H7 and screening for non-O157 Shiga toxin-producing E. coli. BMC Microbiol 2017; 17:215. [PMID: 29121863 PMCID: PMC5679507 DOI: 10.1186/s12866-017-1123-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 10/27/2017] [Indexed: 12/22/2022] Open
Abstract
Background Shiga toxin-producing Escherichia coli (STEC), including E. coli O157:H7, are responsible for numerous foodborne outbreaks annually worldwide. E. coli O157:H7, as well as pathogenic non-O157:H7 STECs, can cause life-threating complications, such as bloody diarrhea (hemolytic colitis) and hemolytic-uremic syndrome (HUS). Previously, we developed a real-time PCR assay to detect E. coli O157:H7 in foods by targeting a unique putative fimbriae protein Z3276. To extend the detection spectrum of the assay, we report a multiplex real-time PCR assay to specifically detect E. coli O157:H7 and screen for non-O157 STEC by targeting Z3276 and Shiga toxin genes (stx1 and stx2). Also, an internal amplification control (IAC) was incorporated into the assay to monitor the amplification efficiency. Methods The multiplex real-time PCR assay was developed using the Life Technology ABI 7500 System platform and the standard chemistry. The optimal amplification mixture of the assay contains 12.5 μl of 2 × Universal Master Mix (Life Technology), 200 nM forward and reverse primers, appropriate concentrations of four probes [(Z3276 (80 nM), stx1 (80 nM), stx2 (20 nM), and IAC (40 nM)], 2 μl of template DNA, and water (to make up to 25 μl in total volume). The amplification conditions of the assay were set as follows: activation of TaqMan at 95 °C for 10 min, then 40 cycles of denaturation at 95 °C for 10 s and annealing/extension at 60 °C for 60 s. Results The multiplex assay was optimized for amplification conditions. The limit of detection (LOD) for the multiplex assay was determined to be 200 fg of bacterial DNA, which is equivalent to 40 CFU per reaction which is similar to the LOD generated in single targeted PCRs. Inclusivity and exclusivity determinants were performed with 196 bacterial strains. All E. coli O157:H7 (n = 135) were detected as positive and all STEC strains (n = 33) were positive for stx1, or stx2, or stx1 and stx2 (Table 1). No cross reactivity was detected with Salmonella enterica, Shigella strains, or any other pathogenic strains tested. Conclusions A multiplex real-time PCR assay that can rapidly and simultaneously detect E. coli O157:H7 and screen for non-O157 STEC strains has been developed and assessed for efficacy. The inclusivity and exclusivity tests demonstrated high sensitivity and specificity of the multiplex real-time PCR assay. In addition, this multiplex assay was shown to be effective for the detection of E. coli O157:H7 from two common food matrices, beef and spinach, and may be applied for detection of E. coli O157:H7 and screening for non-O157 STEC strains from other food matrices as well.
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Affiliation(s)
- Baoguang Li
- Division of Molecular Biology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD, 20708, USA.
| | - Huanli Liu
- Branch of Microbiology, Office of Regulatory Affairs, Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Weimin Wang
- Division of Molecular Biology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, Laurel, MD, 20708, USA
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Siddamallaiah L, Mohapatra S, Buddidathi R, Hebbar SS. Dissipation of spiromesifen and spiromesifen-enol on tomato fruit, tomato leaf, and soil under field and controlled environmental conditions. Environ Sci Pollut Res Int 2017; 24:23559-23570. [PMID: 28852956 DOI: 10.1007/s11356-017-9954-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 08/11/2017] [Indexed: 06/07/2023]
Abstract
Dissipation of spiromesifen and its metabolite, spiromesifen-enol, on tomato fruit, tomato leaf, and soil was studied in the open field and controlled environmental conditions. Sample preparation was carried out by QuEChERS method and analysis using LC-MS/MS. Method validation for analysis of the compounds was carried out as per "single laboratory method validation guidelines." Method validation studies gave satisfactory recoveries for spiromesifen and spiromesifen-enol (71.59-105.3%) with relative standard deviation (RSD) < 20%. LOD and LOQ of the method were 0.0015 μg mL-1 and 0.005 mg kg-1, respectively. Spiromesifen residues on tomato fruits were 0.855 and 1.545 mg kg-1 in open field and 0.976 and 1.670 mg kg-1 under polyhouse condition, from treatments at the standard and double doses of 125 and 250 g a.i. ha-1, respectively. On tomato leaves, the residues were 5.64 and 8.226 mg kg-1 in open field and 6.874 and 10.187 mg kg-1 in the polyhouse. In soil, the residues were 0.532 and 1.032 mg kg-1 and 0.486 and 0.925 mg kg-1 under open field and polyhouse conditions, respectively. The half-life of degradation of spiromesifen on tomato fruit was 6-6.5 days in the open field and 8.1-9.3 days in the polyhouse. On tomato leaves, it was 7-7.6 and 17.6-18.4 days and in soil 5.6-7.4 and 8.4-9.5 days, respectively. Metabolite, spiromesifen-enol, was not detected in any of the sample throughout the study period. Photodegradation could be the major route for dissipation of spiromesifen in the tomato leaves, whereas in the fruits, it may be the combination of photodegradation and dilution due to fruit growth. The results of the study can be utilized for application of spiromesifen in plant protection of tomato crop under protected environmental conditions.
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Affiliation(s)
- Lekha Siddamallaiah
- Pesticide Residue Laboratory, ICAR-Indian Institute of Horticultural Research, Hesaraghatta Lake P.O., Bangalore, Karnataka, 560089, India
- Center for Postgraduate Studies (Jain University), 18/3, 9th Main, 3rd Block, Jayanagar, Bangalore, 560011, India
| | - Soudamini Mohapatra
- Pesticide Residue Laboratory, ICAR-Indian Institute of Horticultural Research, Hesaraghatta Lake P.O., Bangalore, Karnataka, 560089, India.
| | - Radhika Buddidathi
- Pesticide Residue Laboratory, ICAR-Indian Institute of Horticultural Research, Hesaraghatta Lake P.O., Bangalore, Karnataka, 560089, India
| | - Shibara Shankara Hebbar
- Division of Vegetable Crops, Indian Institute of Horticultural Research, Hesaraghatta Lake P.O., Bangalore, Karnataka, 560089, India
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Brkljača R, Urban S. Limit of detection studies for application to natural product identification using high performance liquid chromatography coupled to nuclear magnetic resonance spectroscopy. J Chromatogr A 2015; 1375:69-75. [PMID: 25498554 DOI: 10.1016/j.chroma.2014.11.074] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 10/16/2014] [Accepted: 11/27/2014] [Indexed: 10/24/2022]
Abstract
In the pursuit of new natural products, the demand to rapidly identify compounds present, in ever decreasing amounts, in complex crude extracts has become a limiting factor. Despite improvements in HPLC-NMR hardware and pulse sequences, no extensive limit of detection (LOD) investigations have been reported for the acquisition of 2D NMR spectroscopic experiments acquired through HPLC-NMR. In this study the LOD for five key 1D and 2D NMR spectroscopic experiments have been established, using two reference compounds, including the on-flow (WET 1D proton), stop-flow (WET1D proton), gCOSY, HSQCAD and gHMBCAD NMR experiments. The LOD for all of the NMR experiments were within the range of 700ng to 1mg for the set of fixed experimental parameters implemented. For principle components in a complex multi-component mixture, this would allow for in situ compound identification. HPLC-NMR analysis was employed to investigate the principle components present in a marine brown alga crude extract, Cystophora subfarcinata.
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Affiliation(s)
- Robert Brkljača
- School of Applied Sciences, Health Innovations Research Institute (HIRi), RMIT University, GPO Box 2476V, Melbourne, Victoria 3001, Australia
| | - Sylvia Urban
- School of Applied Sciences, Health Innovations Research Institute (HIRi), RMIT University, GPO Box 2476V, Melbourne, Victoria 3001, Australia.
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