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Liang T, Chen J, Yan R, Jiang H, Li H. Research on Detection of Ultra-Low Concentration Anthrax Protective Antigen Using Graphene Field-Effect Transistor Biosensor. SENSORS (BASEL, SWITZERLAND) 2023; 23:5820. [PMID: 37447669 DOI: 10.3390/s23135820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 05/28/2023] [Accepted: 06/01/2023] [Indexed: 07/15/2023]
Abstract
BACKGROUND Protective antigen (PA) is an important biomarker for the early diagnosis of anthrax, and the accurate detection of protective antigen under extremely low concentration conditions has always been a hot topic in the biomedical field. To complete the diagnosis of anthrax in a timely manner, it is necessary to detect PA at extremely low concentrations, as the amount of PA produced in the early stage of anthrax invasion is relatively small. Graphene field-effect transistor (Gr-FET) biosensors are a new type of material for preparing biosensors, with the advantages of a short detection time and ultra-low detection limit. METHODS The effect of different concentrations of diluents on the affinity of PA monoclonal antibodies was determined via an ELISA experiment. Combined with the Debye equation, 0.01 × PBS solution was finally selected as the diluent for the experiment. Then, a PA monoclonal antibody was selected as the bio-recognition element to construct a Gr-FET device based on CVD-grown graphene, which was used to detect the concentration of PA while recording the response time, linear range, detection limit, and other parameters. RESULTS The experimental results showed that the biosensor could quickly detect PA, with a linear range of 10 fg/mL to 100 pg/mL and a detection limit of 10 fg/mL. In addition, the biosensor showed excellent specificity and repeatability. CONCLUSIONS By constructing a Gr-FET device based on CVD-grown graphene and selecting a PA monoclonal antibody as the bio-recognition element, a highly sensitive, specific, and repeatable Gr-FET biosensor was successfully prepared for detecting extremely low concentrations of anthrax protective antigen (PA). This biosensor is expected to have a wide range of applications in clinical medicine and biological safety monitoring.
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Affiliation(s)
- Ting Liang
- The Institute of NBC Defense PLA Army, Beijing 102205, China
| | | | - Rui Yan
- The Institute of NBC Defense PLA Army, Beijing 102205, China
| | - Huaning Jiang
- The Institute of NBC Defense PLA Army, Beijing 102205, China
- Unit No. 32281 of PLA, Chengdu 610200, China
| | - Hexi Li
- The Institute of NBC Defense PLA Army, Beijing 102205, China
- Unit No. 31666 of PLA, Zhangye 610200, China
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Sreenan B, Lee B, Wan L, Zeng R, Zhao J, Zhu X. Review of Mn-Doped Semiconductor Nanocrystals for Time-Resolved Luminescence Biosensing/Imaging. ACS APPLIED NANO MATERIALS 2022; 5:17413-17435. [PMID: 36874078 PMCID: PMC9980291 DOI: 10.1021/acsanm.2c04337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Colloidal semiconductor nanocrystals (NCs) have been developed for decades and are widely applied in biosensing/imaging. However, their biosensing/imaging applications are mainly based on luminescence-intensity measurement, which suffers from autofluorescence in complex biological samples and thus limits the biosensing/imaging sensitivities. It is expected for these NCs to be further developed to gain luminescence features that can overcome sample autofluorescence. On the other hand, time-resolved luminescence measurement utilizing long-lived-luminescence probes is an efficient technique to eliminate short-lived autofluorescence of samples while recording time-resolved luminescence of the probes for signal measurement after pulsed excitation from a light source. Despite time-resolved measurement being very sensitive, the optical limitations of many of the current long-lived-luminescence probes cause time-resolved measurement to be generally performed in laboratories with bulky and costly instruments. In order to apply highly sensitive time-resolved measurement for in-field or point-of-care (POC) testing, it is essential to develop probes possessing high brightness, low-energy (visible-light) excitation, and long lifetimes of up to milliseconds. Such desired optical features can significantly simplify the design criteria of time-resolved measurement instruments and facilitate the development of low-cost, compact, sensitive instruments for in-field or POC testing. Mn-doped NCs have recently been in rapid development and provide a strategy to solve the challenges faced by both colloidal semiconductor NCs and time-resolved luminescence measurement. In this review, we outline the major achievements in the development of Mn-doped binary and multinary NCs, with emphasis on their synthesis approaches and luminescence mechanisms. Specifically, we demonstrate how researchers approached these obstacles to achieve the aforementioned desired optical properties on the basis of the progressive understanding of Mn emission mechanisms. Afterward, we review representative applications of Mn-doped NCs in time-resolved luminescence biosensing/imaging and present the potential of Mn-doped NCs in advancing time-resolved luminescence biosensing/imaging for in-field or POC testing.
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Affiliation(s)
- Benjamin Sreenan
- Department of Electrical and Biomedical Engineering, University of Nevada-Reno, Reno, Nevada 89557, United States
| | - Bryan Lee
- Department of Electrical and Biomedical Engineering, University of Nevada-Reno, Reno, Nevada 89557, United States
| | - Li Wan
- Department of Physics, Wenzhou University, Wenzhou 325035, China
| | - Ruosheng Zeng
- School of Physical Science and Technology, Guangxi University, Nanning 530004, China
| | - Jialong Zhao
- School of Physical Science and Technology, Guangxi University, Nanning 530004, China
| | - Xiaoshan Zhu
- Department of Electrical and Biomedical Engineering, University of Nevada-Reno, Reno, Nevada 89557, United States
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Nakamura K, Tokuda C, Arimitsu H, Etoh Y, Hamasaki M, Deguchi Y, Taniguchi I, Gotoh Y, Ogura Y, Hayashi T. Development of a homogeneous time-resolved FRET (HTRF) assay for the quantification of Shiga toxin 2 produced by E. coli. PeerJ 2021; 9:e11871. [PMID: 34395095 PMCID: PMC8325423 DOI: 10.7717/peerj.11871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/06/2021] [Indexed: 11/20/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) is a major intestinal pathogen and causes serious gastrointestinal illness, which includes diarrhea, hemorrhagic colitis, and life-threatening hemolytic uremic syndrome. The major virulence factors of STEC are Shiga toxins (Stx1 and Stx2), which belong to the AB-type toxin family. Among several subtypes of Stx1 and Stx2, the production of Stx2a is thought to be a risk factor for severe STEC infections, but Stx2a production levels vary markedly between STEC strains, even strains with the same serotype. Therefore, quantitative analyses of Stx2 production by STEC strains are important to understand the virulence potential of specific lineages or sublineages. In this study, we developed a novel Stx2 quantification method by utilizing homogeneous time-resolved fluorescence resonance energy transfer (HTRF) technology. To determine suitable “sandwich” assay conditions, we tested 6 combinations of fluorescence-labeled monoclonal antibodies (mAbs) specific to Stx2 and compared the HTRF signal intensities obtained at various incubation times. Through this analysis, we selected the most suitable mAb pair, one recognizing the A subunit and the other recognizing the B subunit, thus together detecting Stx holotoxins. The optimal incubation time was also determined (18 h). Then, we optimized the concentrations of the two mAbs based on the range for linearity. The established HTRF assay detected 0.5 ng/ml of the highly purified recombinant Stx2a and Stx2e proteins and the working range was 1–64 ng/ml for both Stx2a and Stx2e. Through the quantification analysis of Stx proteins in STEC cell lysates, we confirmed that other Stx2 subtypes (Stx2b, Stx2c, Stx2d and Stx2g) can also be quantified at a certain level of accuracy, while this assay system does not detect Stx2f, which is highly divergent in sequence from other Stx2 subtypes, and Stx1. As the HTRF protocol we established is simple, this assay system should prove useful for the quantitative analysis of Stx2 production levels of a large number of STEC strains.
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Affiliation(s)
- Keiji Nakamura
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | - Hideyuki Arimitsu
- School of Human Science and Environment, University of Hyogo, Himeji, Japan
| | - Yoshiki Etoh
- Fukuoka Institute of Health and Environmental Sciences, Dazaifu, Japan
| | | | - Yuichiro Deguchi
- Production Medicine Center, Agricultural Mutual Aid Association in Miyazaki Prefecture, Koyugun-Shintomicho, Japan
| | - Itsuki Taniguchi
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yasuhiro Gotoh
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshitoshi Ogura
- Division of Microbiology, Department of Infectious Medicine, Kurume University School of Medicine, Kurume, Japan
| | - Tetsuya Hayashi
- Department of Bacteriology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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Li Y, Wang J, Tian Y, Huang Z, Qian C, Duan Y. The development of a wash-free homogeneous immunoassay method for the detection of tetracycline in environmental samples. Analyst 2021; 146:4918-4926. [PMID: 34250990 DOI: 10.1039/d1an00929j] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Antibiotic residues have become the major source of environmental pollutants. In order to monitor tetracycline (TC) in the environment, we have established a highly sensitive and wash-free homogeneous time-resolved immunoassay. This analytical method was based on a rare earth chelate with excellent fluorescence properties. The cryptate organic ligand had good stability and acted as an antenna for Eu3+ excitation. In a homogeneous system, the Eu3+ cryptate complex was used as a label to bind to antibodies. Under the action of immunoaffinity, fluorescent donors and acceptors were close to each other, which induced the FRET effect to produce proportional fluorescence. Under the optimal parameters, the half-inhibitory concentration (IC50) and limit of detection (LOD, IC10) of TC were 0.4188 ng mL-1 and 0.0106 ng mL-1, respectively. The linear range (IC20-IC80) was 0.0273-9.2645 ng mL-1. With the environmental samples, the recovery rate of TC was 84.3-107.2%, and the standard deviation (RSD) was 4.6-12.9%. The results showed the good sensitivity and reliability of the method. Compared with the traditional ELISA, our method has less background interference, only one step was required without the washing procedure, and the detection result can be obtained by 30 min incubation, which improves the detection efficiency. Because of the characteristics of immunoassays, different pollutants can be monitored by changing the antibodies. This method provides an alternative path for detecting environmental pollutants and has the potential to develop into an on-site detection kit.
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Affiliation(s)
- Yinjun Li
- Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China. and Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Jiayu Wang
- Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China. and Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Yonghui Tian
- Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China. and Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Zhijun Huang
- Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China. and Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China
| | - Cheng Qian
- Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an, 710127, China
| | - Yixiang Duan
- Research Center of Analytical Instrumentation, Northwest University, Xi'an, Shaanxi 710069, China. and Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710069, China
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Epitope Binning of Novel Monoclonal Anti F1 and Anti LcrV Antibodies and Their Application in a Simple, Short, HTRF Test for Clinical Plague Detection. Pathogens 2021; 10:pathogens10030285. [PMID: 33801490 PMCID: PMC8001648 DOI: 10.3390/pathogens10030285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 11/18/2022] Open
Abstract
Mouse monoclonal antibodies were raised against plague disease biomarkers: the bacterial capsular protein fraction 1 (F1) and the low-calcium response—LcrV virulence factor (Vag). A novel tandem assay, employing BioLayer Interferometry (BLI), enabled the isolation of antibodies against four different epitopes on Vag. The tandem assay was carried out with hybridoma supernatants, circumventing the need for antibody purification. The BioLayer assay was further adopted for characterization of epitope-repetitive antigens, enabling the discovery of two unique epitopes on F1. The selected antibodies were purified and applied as “oligo-clonal” reagents for the immuno-detection of both biomarkers. The developed Homogenous Time Resolved Fluorescence (HTRF) tests were short (10 min) and simple (no washing steps), allowing for detection of 10 ng/mL F1 and 2.5 ng/mL Vag. The tests were successfully applied for detection of disease biomarkers produced by various Y. pestis strains during growth in blood culture vials.
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Tournier JN, Rougeaux C. Anthrax Toxin Detection: From In Vivo Studies to Diagnostic Applications. Microorganisms 2020; 8:microorganisms8081103. [PMID: 32717946 PMCID: PMC7464488 DOI: 10.3390/microorganisms8081103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 07/19/2020] [Accepted: 07/21/2020] [Indexed: 11/16/2022] Open
Abstract
Anthrax toxins are produced by Bacillus anthracis throughout infection and shape the physiopathogenesis of the disease. They are produced in low quantities but are highly efficient. They have thus been long ignored, but recent biochemical methods have improved our knowledge in animal models. This article reviews the various methods that have been used and how they could be applied to clinical diagnosis.
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Affiliation(s)
- Jean-Nicolas Tournier
- Unité Bactériologie Biothérapies Anti-infectieuses et Immunité, Institut de Recherche Biomédicale des Armées (IRBA), 1 place Général Valérie André, 91220 Brétigny sur Orge, France;
- Centre National de Référence-Laboratoire Expert Charbon, 1 place Général Valérie André, 91220 Brétigny sur Orge, France
- Innovative Vaccine Laboratory, Institut Pasteur, 28 rue du docteur Roux, 75015 Paris, France
- Ecole du Val-de-Grâce, 1 place Alphonse Laveran, 75005 Paris, France
| | - Clémence Rougeaux
- Unité Bactériologie Biothérapies Anti-infectieuses et Immunité, Institut de Recherche Biomédicale des Armées (IRBA), 1 place Général Valérie André, 91220 Brétigny sur Orge, France;
- Centre National de Référence-Laboratoire Expert Charbon, 1 place Général Valérie André, 91220 Brétigny sur Orge, France
- Correspondence: ; Tel.: +33-178-651-891
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Velázquez-López I, León-Cruz E, Pardo JP, Sosa-Peinado A, González-Andrade M. Development of new hCaM-Alexa Fluor ® biosensors for a wide range of ligands. Anal Biochem 2017; 516:13-22. [PMID: 27744023 DOI: 10.1016/j.ab.2016.10.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 10/05/2016] [Accepted: 10/11/2016] [Indexed: 11/17/2022]
Abstract
Eight new fluorescent biosensors of human calmodulin (hCaM) using Alexa Fluor® 350, 488, 532, and 555 dyes were constructed. These biosensors are thermodynamically stable, functional, and highly sensitive to ligands of the CaM. They resolve the problem of CaM ligands with similar spectroscopic properties to the intrinsic and extrinsic fluorophores of other biosensors previously reported. Additionally, they can be used in studies of protein-protein interaction through Förster resonance energy transfer (FRET). The variation in Tm (range 78.07-81.47 °C; 79.05 to WT) is no larger than two degrees in all cases in regards to CaM WT. The Kds calculated with all biosensors for CPZ and BIMI (a new inhibitor of CaM) are in the range of 0.45-1.86 and 0.69-1.54 μm respectively. All biosensors retain their ability to activate Calcineurin about 70%. Structural models built "in silico" show their possible conformation taking the fluorophores in protein thus we can predict system stability. Finally, these new biosensors represent a biotechnological development applied to an analytical problem, which aims to determine accurately the affinity of inhibitors of CaM without possible interference, to be put forward as possible drugs related to CaM.
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Affiliation(s)
- I Velázquez-López
- Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, C.P 04510, Mexico
| | - E León-Cruz
- Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, C.P 04510, Mexico
| | - J P Pardo
- Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, C.P 04510, Mexico
| | - A Sosa-Peinado
- Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, C.P 04510, Mexico
| | - M González-Andrade
- Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, C.P 04510, Mexico.
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Cohen N, Zahavy E, Zichel R, Fisher M. An internal standard approach for homogeneous TR-FRET immunoassays facilitates the detection of bacteria, biomarkers, and toxins in complex matrices. Anal Bioanal Chem 2016; 408:5179-88. [PMID: 27236318 DOI: 10.1007/s00216-016-9602-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 04/13/2016] [Accepted: 04/25/2016] [Indexed: 10/21/2022]
Abstract
The recent development of a homogeneous time-resolved Förster resonance energy transfer (TR-FRET) immunoassay enables one-step, rapid (minutes), and direct detection compared to the multistep, time-consuming (hours), heterogeneous ELISA-type immunoassays. The use of the time-resolved effect of a donor lanthanide complex with a delay time of microseconds and large Stokes shift enables the separation of positive signals from the background autofluorescence of the sample. However, this study shows that the sample matrices directly interfere with donor fluorescence and that interference cannot be eliminated by time-resolved settings alone. Moreover, the reduction in donor emission did not appear to be equivalent to the reduction in acceptor emission, resulting in incorrect FRET signal measurements. To overcome this limitation, an internal standard approach was developed using an isotype control antibody. This new approach was used to develop TR-FRET assays for rapid detection (15-30 min) of Bacillus anthracis spores and botulinum toxin (type E) in beverages, which are major concerns in bioterrorism involving deliberate food contamination. Additionally, we demonstrate the detection of B. anthracis-secreted protective antigen (PA) and the Yersinia pestis-secreted markers F1 and LcrV in blood cultures, which are early markers of bacteremia in infected hosts following a possible bioterror attack. The use of an internal standard enables the calculation of correct ΔF values without the need for an external standard. Thus, the use of the internal standard approach in homogeneous immunoassays facilitates the examination of any sample regardless of its origin, and therefore expands the applicability of TR-FRET assays for complex matrices.
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Affiliation(s)
- Noam Cohen
- Department of Biotechnology, Israel Institute for Biological Research, Ness-Ziona, 74100, Israel
| | - Eran Zahavy
- Department of Infectious Diseases, Israel Institute for Biological Research, Ness-Ziona, 74100, Israel
| | - Ran Zichel
- Department of Biotechnology, Israel Institute for Biological Research, Ness-Ziona, 74100, Israel
| | - Morly Fisher
- Department of Infectious Diseases, Israel Institute for Biological Research, Ness-Ziona, 74100, Israel.
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Signal Improvement Strategies for Fluorescence Detection of Biomacromolecules. J Fluoresc 2016; 26:1131-9. [DOI: 10.1007/s10895-016-1806-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 03/27/2016] [Indexed: 12/19/2022]
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Siraj N, El-Zahab B, Hamdan S, Karam TE, Haber LH, Li M, Fakayode SO, Das S, Valle B, Strongin RM, Patonay G, Sintim HO, Baker GA, Powe A, Lowry M, Karolin JO, Geddes CD, Warner IM. Fluorescence, Phosphorescence, and Chemiluminescence. Anal Chem 2015; 88:170-202. [PMID: 26575092 DOI: 10.1021/acs.analchem.5b04109] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Noureen Siraj
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Bilal El-Zahab
- Department of Mechanical and Materials Engineering, Florida International University , Miami, Florida 33174, United States
| | - Suzana Hamdan
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Tony E Karam
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Louis H Haber
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Min Li
- Process Development Center, Albemarle Corporation , Baton Rouge, Louisiana 70805, United States
| | - Sayo O Fakayode
- Department of Chemistry, Winston-Salem State University , Winston-Salem, North Carolina 27110, United States
| | - Susmita Das
- Department of Civil Engineering, Adamas Institute of Technology , Barasat, Kolkata 700126, West Bengal India
| | - Bertha Valle
- Department of Chemistry, Texas Southern University , Houston, Texas 77004, United States
| | - Robert M Strongin
- Department of Chemistry, Portland State University , Portland, Oregon 97207, United States
| | - Gabor Patonay
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30302-4098, United States
| | - Herman O Sintim
- Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States
| | - Gary A Baker
- Department of Chemistry, University of Missouri Columbia , Columbia, Missouri 65211-7600, United States
| | - Aleeta Powe
- Department of Chemistry, University of Louisville , Louisville, Kentucky 40208, United States
| | - Mark Lowry
- Department of Chemistry, Portland State University , Portland, Oregon 97207, United States
| | - Jan O Karolin
- Institute of Fluorescence, University of Maryland Baltimore County , Baltimore, Maryland 21202, United States
| | - Chris D Geddes
- Institute of Fluorescence, University of Maryland Baltimore County , Baltimore, Maryland 21202, United States
| | - Isiah M Warner
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
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High-sensitivity MALDI-TOF MS quantification of anthrax lethal toxin for diagnostics and evaluation of medical countermeasures. Anal Bioanal Chem 2015; 407:2847-58. [PMID: 25673244 PMCID: PMC4369318 DOI: 10.1007/s00216-015-8509-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/13/2015] [Accepted: 01/21/2015] [Indexed: 11/15/2022]
Abstract
Inhalation anthrax has a rapid progression and high fatality rate. Pathology and death from inhalation of Bacillus anthracis spores are attributed to the actions of secreted protein toxins. Protective antigen (PA) binds and imports the catalytic component lethal factor (LF), a zinc endoprotease, and edema factor (EF), an adenylyl cyclase, into susceptible cells. PA-LF is termed lethal toxin (LTx) and PA-EF, edema toxin. As the universal transporter for both toxins, PA is an important target for vaccination and immunotherapeutic intervention. However, its quantification has been limited to methods of relatively low analytic sensitivity. Quantification of LTx may be more clinically relevant than LF or PA alone because LTx is the toxic form that acts on cells. A method was developed for LTx-specific quantification in plasma using anti-PA IgG magnetic immunoprecipitation of PA and quantification of LF activity that co-purified with PA. The method was fast (<4 h total time to detection), sensitive at 0.033 ng/mL LTx in plasma for the fast analysis (0.0075 ng/mL LTx in plasma for an 18 h reaction), precise (6.3–9.9 % coefficient of variation), and accurate (0.1–12.7 %error; n ≥ 25). Diagnostic sensitivity was 100 % (n = 27 animal/clinical cases). Diagnostic specificity was 100 % (n = 141). LTx was detected post-antibiotic treatment in 6/6 treated rhesus macaques and 3/3 clinical cases of inhalation anthrax and as long as 8 days post-treatment. Over the course of infection in two rhesus macaques, LTx was first detected at 0.101 and 0.237 ng/mL at 36 h post-exposure and increased to 1147 and 12,107 ng/mL in late-stage anthrax. This demonstrated the importance of LTx as a diagnostic and therapeutic target. This method provides a sensitive, accurate tool for anthrax toxin detection and evaluation of PA-directed therapeutics. Method schematic for analysis of anthrax lethal toxin activity by ID-MALDI-TOF MS ![]()
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