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Consequences of the Edge Effect in a Commercial Enzyme-Linked Immunosorbent Assay for the Diagnosis of Lyme Neuroborreliosis. J Clin Microbiol 2021; 59:e0328020. [PMID: 33980651 PMCID: PMC8288263 DOI: 10.1128/jcm.03280-20] [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] [Indexed: 11/20/2022] Open
Abstract
The diagnosis of Lyme neuroborreliosis (LNB) is based on neurological symptoms, cerebrospinal fluid (CSF) pleocytosis, and intrathecally produced Borrelia-specific antibodies. In most cases, the presence of intrathecally produced Borrelia-specific antibodies is determined by using an enzyme-linked immunosorbent assay (ELISA). The edge effect is a known phenomenon in ELISAs and can negatively influence the assay reproducibility and repeatability, as well as index calculations of sample pairs which are tested in the same run. For LNB diagnostics, an index calculation is used for which the relative amounts of Borrelia-specific antibodies in CSF and serum are measured to calculate a CSF/serum quotient, which is needed to calculate the Borrelia-specific antibody index (AI). The presence of an edge effect in an ELISA used for LNB diagnostics may thus have implications. In this study, we investigated the intra-assay variation of the commercial Enzygnost Lyme link VlsE/IgG ELISA used for LNB diagnostics and showed the presence of an edge effect. Minor adaptations in the ELISA protocol decreased this effect. The adapted protocol was subsequently used to test 149 CSF-serum pairs of consecutive patients received in a routine diagnostic laboratory. By simulation, we showed that, if the standard protocol would have been used, then the edge effect for this study population could have resulted in 15 (10.1%) false-pathological and two (1.3%) false-normal Borrelia-specific IgG AIs. Thus, the observed edge effect can lead to inaccurate LNB diagnoses. Our study underlines that the edge effect should be investigated when ELISAs are implemented in routine diagnostics, as this phenomenon can occur in any ELISA.
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Lankatillake C, Luo S, Flavel M, Lenon GB, Gill H, Huynh T, Dias DA. Screening natural product extracts for potential enzyme inhibitors: protocols, and the standardisation of the usage of blanks in α-amylase, α-glucosidase and lipase assays. PLANT METHODS 2021; 17:3. [PMID: 33407662 PMCID: PMC7789656 DOI: 10.1186/s13007-020-00702-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 12/19/2020] [Indexed: 06/01/2023]
Abstract
BACKGROUND Enzyme assays have widespread applications in drug discovery from plants to natural products. The appropriate use of blanks in enzyme assays is important for assay baseline-correction, and the correction of false signals associated with background matrix interferences. However, the blank-correction procedures reported in published literature are highly inconsistent. We investigated the influence of using different types of blanks on the final calculated activity/inhibition results for three enzymes of significance in diabetes and obesity; α-glucosidase, α-amylase, and lipase. This is the first study to examine how different blank-correcting methods affect enzyme assay results. Although assays targeting the above enzymes are common in the literature, there is a scarcity of detailed published protocols. Therefore, we have provided comprehensive, step-by-step protocols for α-glucosidase-, α-amylase- and lipase-inhibition assays that can be performed in 96-well format in a simple, fast, and resource-efficient manner with clear instructions for blank-correction and calculation of results. RESULTS In the three assays analysed here, using only a buffer blank underestimated the enzyme inhibitory potential of the test sample. In the absorbance-based α-glucosidase assay, enzyme inhibition was underestimated when a sample blank was omitted for the coloured plant extracts. Similarly, in the fluorescence-based α-amylase and lipase assays, enzyme inhibition was underestimated when a substrate blank was omitted. For all three assays, method six [Raw Data - (Substrate + Sample Blank)] enabled the correction of interferences due to the buffer, sample, and substrate without double-blanking, and eliminated the need to add substrate to each sample blank. CONCLUSION The choice of blanks and blank-correction methods contribute to the variability of assay results and the likelihood of underestimating the enzyme inhibitory potential of a test sample. This highlights the importance of standardising the use of blanks and the reporting of blank-correction procedures in published studies in order to ensure the accuracy and reproducibility of results, and avoid overlooked opportunities in drug discovery research due to inadvertent underestimation of enzyme inhibitory potential of test samples resulting from unsuitable blank-correction. Based on our assessments, we recommend method six [RD - (Su + SaB)] as a suitable method for blank-correction of raw data in enzyme assays.
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Affiliation(s)
- Chintha Lankatillake
- School of Health and Biomedical Sciences, Discipline of Laboratory Medicine, RMIT University, Bundoora, 3083, Australia
| | - Shiqi Luo
- School of Health and Biomedical Sciences, Discipline of Laboratory Medicine, RMIT University, Bundoora, 3083, Australia
| | - Matthew Flavel
- TPM Bioactives Division, The Product Makers Pty Ltd, Melbourne, Australia
- School of Life Sciences, La Trobe University, Melbourne, Australia
| | - George Binh Lenon
- School of Health and Biomedical Sciences, Discipline of Laboratory Medicine, RMIT University, Bundoora, 3083, Australia
| | - Harsharn Gill
- School of Science, RMIT University, Bundoora, 3083, Australia
| | - Tien Huynh
- School of Science, RMIT University, Bundoora, 3083, Australia
| | - Daniel Anthony Dias
- School of Health and Biomedical Sciences, Discipline of Laboratory Medicine, RMIT University, Bundoora, 3083, Australia.
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Soori T, Ward T. De-pinning instability of an evaporating-bounded liquid bridge: Experiments and axisymmetric analysis. Colloids Surf A Physicochem Eng Asp 2020. [DOI: 10.1016/j.colsurfa.2020.124664] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Singh N, Herzer S. Downstream Processing Technologies/Capturing and Final Purification : Opportunities for Innovation, Change, and Improvement. A Review of Downstream Processing Developments in Protein Purification. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2019; 165:115-178. [PMID: 28795201 DOI: 10.1007/10_2017_12] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Increased pressure on upstream processes to maximize productivity has been crowned with great success, although at the cost of shifting the bottleneck to purification. As drivers were economical, focus is on now on debottlenecking downstream processes as the main drivers of high manufacturing cost. Devising a holistically efficient and economical process remains a key challenge. Traditional and emerging protein purification strategies with particular emphasis on methodologies implemented for the production of recombinant proteins of biopharmaceutical importance are reviewed. The breadth of innovation is addressed, as well as the challenges the industry faces today, with an eye to remaining impartial, fair, and balanced. In addition, the scope encompasses both chromatographic and non-chromatographic separations directed at the purification of proteins, with a strong emphasis on antibodies. Complete solutions such as integrated USP/DSP strategies (i.e., continuous processing) are discussed as well as gains in data quantity and quality arising from automation and high-throughput screening (HTS). Best practices and advantages through design of experiments (DOE) to access a complex design space such as multi-modal chromatography are reviewed with an outlook on potential future trends. A discussion of single-use technology, its impact and opportunities for further growth, and the exciting developments in modeling and simulation of DSP rounds out the overview. Lastly, emerging trends such as 3D printing and nanotechnology are covered. Graphical Abstract Workflow of high-throughput screening, design of experiments, and high-throughput analytics to understand design space and design space boundaries quickly. (Reproduced with permission from Gregory Barker, Process Development, Bristol-Myers Squibb).
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Affiliation(s)
- Nripen Singh
- Bristol-Myers Squibb, Global Manufacturing and Supply, Devens, MA, 01434, USA.
| | - Sibylle Herzer
- Bristol-Myers Squibb, Global Manufacturing and Supply, Hopewell, NJ, 01434, USA
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On the practical aspects of characterising monoamine oxidase inhibition in vitro. J Neural Transm (Vienna) 2018; 125:1685-1705. [PMID: 30374594 DOI: 10.1007/s00702-018-1943-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 10/13/2018] [Indexed: 10/28/2022]
Abstract
The development of novel inhibitors of human monoamine oxidase enzymes with improved pharmacodynamic and pharmacokinetic profiles has, in the past, been hampered by limited access to enzyme, by assay protocols offering limited throughput, and by inappropriate analyses of kinetic data. More recently, high-level expression of human enzymes in yeast has facilitated thorough examinations of steady-state enzyme behaviour that have led to improvements in our understanding of the mathematical underpinnings of kinetic analyses of monoamine oxidases. However, with these improvements have come a realisation that to be useful, more data points across wider concentration ranges are required. In turn, many discontinuous assay approaches, such as those involving radiolabelled substrates or chromatographic separation of product from substrate, have been rendered somewhat obsolete. Justification for the use of a platereader-based approach to assess the effects of novel inhibitors on monamine oxidases is provided, along with details of experimental design optimised to address the unexpectedly complex kinetics followed by these enzymes. Potential sources of error are discussed, and comments provided on techniques that may enhance the quality of experimental data.
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Lilyanna S, Ng EMW, Moriguchi S, Chan SP, Kokawa R, Huynh SH, Chong PCJ, Ng YX, Richards AM, Ng TW, Liew OW. Variability in Microplate Surface Properties and Its Impact on ELISA. J Appl Lab Med 2017; 2:687-699. [PMID: 33636870 DOI: 10.1373/jalm.2017.023952] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 08/18/2017] [Indexed: 11/06/2022]
Abstract
BACKGROUND Microplate-based immunoassays are widely used in clinical and research settings to measure a broad range of biomarkers present in complex matrices. Assay variability within and between microplates can give rise to false-negative and false-positive results leading to incorrect conclusions. To date, the contribution of microplates to this variability remains poorly characterized and described. This study provides new insights into variability in immunoassays attributable to surface characteristics of commercial microplates. METHODS Well-to-well assay variation in γ-treated and nontreated 96-well opaque microplates suitable for chemiluminescence assays was determined by use of a validated sandwich ELISA. Microplate surface characteristics were assessed by sessile drop contact angle measurements, scanning electron microscopy, energy dispersive x-ray spectroscopy, and atomic force microscopy. RESULTS All microplate types tested exhibited vendor-specific assay response profiles; and "rogue" plates with very high intraassay variation and deviant mean assay responses were found. Within-plate, location-dependent bias in assay responses and variability in well contact angle were also observed. We demonstrate substantial differences in well-surface properties with putative effects on protein-coating reproducibility and hence consistency in immunoassay responses. A surface "cleaning" effect on manufacturing residues was attributed to γ-irradiation, and treated microplates manifest increased polar functionalities, surface roughness, and assay responses. CONCLUSIONS Our data suggest that tighter control of variability in surface roughness, wettability, chemistry, and level of residual contaminants during microplate preparation is warranted to improve consistency of ELISA assay read out.
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Affiliation(s)
- Shera Lilyanna
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Enoch Ming Wei Ng
- Laboratory for Optics & Applied Mechanics, Department of Mechanical & Aerospace Engineering, Monash University, Clayton, Australia
| | | | - Siew Pang Chan
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Ryohei Kokawa
- Global Application Development Center, Shimadzu Corporation, Japan
| | - So Hung Huynh
- Laboratory for Optics & Applied Mechanics, Department of Mechanical & Aerospace Engineering, Monash University, Clayton, Australia
| | - P C Jenny Chong
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - Yan Xia Ng
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
| | - A Mark Richards
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore.,Christchurch Heart Institute, Department of Medicine, University of Otago, Christchurch, New Zealand
| | - Tuck Wah Ng
- Laboratory for Optics & Applied Mechanics, Department of Mechanical & Aerospace Engineering, Monash University, Clayton, Australia
| | - Oi Wah Liew
- Cardiovascular Research Institute, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore
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Grosch JH, Sieben M, Lattermann C, Kauffmann K, Büchs J, Spieß AC. Enzyme activity deviates due to spatial and temporal temperature profiles in commercial microtiter plate readers. Biotechnol J 2016; 11:519-29. [DOI: 10.1002/biot.201500422] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/08/2015] [Accepted: 12/18/2015] [Indexed: 12/22/2022]
Affiliation(s)
| | - Michaela Sieben
- RWTH Aachen University, AVT - Biochemical Engineering; Aachen Germany
| | | | - Kira Kauffmann
- RWTH Aachen University, AVT - Enzyme Process Technology; Aachen Germany
| | - Jochen Büchs
- RWTH Aachen University, AVT - Enzyme Process Technology; Aachen Germany
| | - Antje C. Spieß
- RWTH Aachen University, AVT - Enzyme Process Technology; Aachen Germany
- DWI - Leibniz-Institute for Interactive Materials; Aachen Germany
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