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Bucur B, Purcarea C, Andreescu S, Vasilescu A. Addressing the Selectivity of Enzyme Biosensors: Solutions and Perspectives. SENSORS (BASEL, SWITZERLAND) 2021; 21:3038. [PMID: 33926034 PMCID: PMC8123588 DOI: 10.3390/s21093038] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 04/13/2021] [Accepted: 04/15/2021] [Indexed: 12/23/2022]
Abstract
Enzymatic biosensors enjoy commercial success and are the subject of continued research efforts to widen their range of practical application. For these biosensors to reach their full potential, their selectivity challenges need to be addressed by comprehensive, solid approaches. This review discusses the status of enzymatic biosensors in achieving accurate and selective measurements via direct biocatalytic and inhibition-based detection, with a focus on electrochemical enzyme biosensors. Examples of practical solutions for tackling the activity and selectivity problems and preventing interferences from co-existing electroactive compounds in the samples are provided such as the use of permselective membranes, sentinel sensors and coupled multi-enzyme systems. The effect of activators, inhibitors or enzymatic substrates are also addressed by coupled enzymatic reactions and multi-sensor arrays combined with data interpretation via chemometrics. In addition to these more traditional approaches, the review discusses some ingenious recent approaches, detailing also on possible solutions involving the use of nanomaterials to ensuring the biosensors' selectivity. Overall, the examples presented illustrate the various tools available when developing enzyme biosensors for new applications and stress the necessity to more comprehensively investigate their selectivity and validate the biosensors versus standard analytical methods.
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Affiliation(s)
- Bogdan Bucur
- National Institute for Research and Development in Biological Sciences, 296 Splaiul Independentei, 060031 Bucharest, Romania;
| | - Cristina Purcarea
- Institute of Biology, 296 Splaiul Independentei, 060031 Bucharest, Romania;
| | - Silvana Andreescu
- Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, NY 13676, USA;
| | - Alina Vasilescu
- International Centre of Biodynamics, 1B Intrarea Portocalelor, 060101 Bucharest, Romania
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Abstract
Over the last few decades the development of new technologies, the fabrication of new materials, and the introduction of nanotechnologies created new trends in a series of advances that produced innovations in biological sensing devices with a wide range of application from health, security, defense, food, and medicine, to the environment. Specificity, low cost, rapidity, sensitivity, and multiplicity are some of the reasons for their growth, and their commercial success is expected to increase in the next future. Biosensors are devices in which the recognition part of the target molecule is accomplished by biological macromolecules such as proteins, enzymes, antibodies, aptamers, etc. These biomolecules are able to bind to the target molecules with high selectivity and specificity. The interaction between the target molecule and the specific biomolecule is reflected as a change of the biomolecule structural features. The extent of this change is strictly related to the biosensor response. Fluorescence spectroscopy, due to its sensitivity, is often used as the principal technique to monitor biological interactions, and thus the biosensor response as well. Both the intrinsic ultraviolet fluorescence of protein, arising from aromatic amino acids (tryptophan, tyrosine, and phenylalanine), and extrinsic fluorescent labels emitting in the visible region of the spectrum together allow for very flexible transduction of the analyte recognition, suitable for many different applications. This chapter focuses special attention on enzymes as practically unmatched recognition elements for biosensors and emphasizes the potential advantages of customized biosensor devices using apo- or holo forms of enzymes also isolated from thermophile sources.
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Abstract
We put forward an impedometric protein-based biosensor platform suitable for point-of-care diagnostics. A hand-held scale impedance reader system is described for the detection of corresponding physiochemical changes as the immobilized proteins bind to the analyte molecules in the proximity of the microfabricated electrodes. Specifically, we study the viability of this approach for glucose biosensing purposes using genetically engineered glucokinase as receptor proteins. The proposed reagent-less biosensor offers a high sensitivity of 0.5 mM glucose concentration level in the physiologically relevant range of 0.5 mM to 7.5 mM with less than 10 s response time.
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Competitive capacitive biosensing technique (CCBT): a novel technique for monitoring low molecular mass analytes using glucose assay as a model study. Anal Bioanal Chem 2010; 397:1217-24. [PMID: 20401723 DOI: 10.1007/s00216-010-3641-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 03/04/2010] [Accepted: 03/07/2010] [Indexed: 01/03/2023]
Abstract
A novel technique for monitoring of low molecular mass analytes using a flow-injection capacitive biosensor is presented. The method is based on the ability of a small molecular mass analyte to displace a large analyte-carrier conjugate from the binding sites of an immobilized biorecognition element with weak affinity to both compounds. A model study was performed on glucose as the small molecular mass analyte. In the absence of glucose, binding of a glucose polymer or a glycoconjugate to concanavalin A results in a capacitance decrease. Upon introduction of glucose, it displaces a part of the bound glucose polymer or glycoconjugate leading to a partial restoration of capacitance. Experimental results show that the change in capacitance depends linearly on glucose concentration within the range from 1.0 x 10(-5) to 1.0 x 10(-1) M, corresponding to 1.8 microg ml(-1) to 18 mg ml(-1) in a logarithmic plot, with a detection limit of 1.0 x 10(-6) (0.18 microg ml(-1)) under optimized conditions. In addition, by modifying the molecular mass of the glucose polymer, amount of biorecognition element, and buffer composition, we were able to tune the analyte-sensing range. The developed technique has the benefits of expanded dynamic range, high sensitivity, and excellent reusability.
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Labib M, Hedström M, Amin M, Mattiasson B. A novel competitive capacitive glucose biosensor based on concanavalin A-labeled nanogold colloids assembled on a polytyramine-modified gold electrode. Anal Chim Acta 2010; 659:194-200. [DOI: 10.1016/j.aca.2009.11.028] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 11/09/2009] [Accepted: 11/11/2009] [Indexed: 10/20/2022]
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Morozkina EV, Slutskaya ES, Fedorova TV, Tugay TI, Golubeva LI, Koroleva OV. Extremophilic microorganisms: Biochemical adaptation and biotechnological application (review). APPL BIOCHEM MICRO+ 2010. [DOI: 10.1134/s0003683810010011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Stein EW, Singh S, McShane MJ. Microscale Enzymatic Optical Biosensors Using Mass Transport Limiting Nanofilms. 2. Response Modulation by Varying Analyte Transport Properties. Anal Chem 2008; 80:1408-17. [DOI: 10.1021/ac701738e] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Erich W. Stein
- Biomedical Engineering Program and Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, and Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843
| | - Saurabh Singh
- Biomedical Engineering Program and Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, and Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843
| | - Michael J. McShane
- Biomedical Engineering Program and Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, and Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843
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Tian Y, Cuneo MJ, Changela A, Höcker B, Beese LS, Hellinga HW. Structure-based design of robust glucose biosensors using a Thermotoga maritima periplasmic glucose-binding protein. Protein Sci 2007; 16:2240-50. [PMID: 17766373 PMCID: PMC2204141 DOI: 10.1110/ps.072969407] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We report the design and engineering of a robust, reagentless fluorescent glucose biosensor based on the periplasmic glucose-binding protein obtained from Thermotoga maritima (tmGBP). The gene for this protein was cloned from genomic DNA and overexpressed in Escherichia coli, the identity of its cognate sugar was confirmed, ligand binding was studied, and the structure of its glucose complex was solved to 1.7 Angstrom resolution by X-ray crystallography. TmGBP is specific for glucose and exhibits high thermostability (midpoint of thermal denaturation is 119 +/- 1 degrees C and 144 +/- 2 degrees C in the absence and presence of 1 mM glucose, respectively). A series of fluorescent conjugates was constructed by coupling single, environmentally sensitive fluorophores to unique cysteines introduced by site-specific mutagenesis at positions predicted to be responsive to ligand-induced conformational changes based on the structure. These conjugates were screened to identify engineered tmGBPs that function as reagentless fluorescent glucose biosensors. The Y13C*Cy5 conjugate is bright, gives a large response to glucose over concentration ranges appropriate for in vivo monitoring of blood glucose levels (1-30 mM), and can be immobilized in an orientation-specific manner in microtiter plates to give a reversible response to glucose. The immobilized protein retains its response after long-term storage at room temperature.
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Affiliation(s)
- Yaji Tian
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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de Champdoré M, Staiano M, Rossi M, D'Auria S. Proteins from extremophiles as stable tools for advanced biotechnological applications of high social interest. J R Soc Interface 2007; 4:183-91. [PMID: 17251151 PMCID: PMC2359841 DOI: 10.1098/rsif.2006.0174] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Accepted: 10/09/2006] [Indexed: 11/12/2022] Open
Abstract
Extremophiles are micro-organisms adapted to survive in ecological niches defined as 'extreme' for humans and characterized by the presence of adverse environmental conditions, such as high or low temperatures, extreme values of pH, high salt concentrations or high pressure. Biomolecules isolated from extremophiles possess extraordinary properties and, in particular, proteins isolated from extremophiles represent unique biomolecules that function under severe conditions, comparable to those prevailing in various industrial processes. In this article, we will review some examples of recent applications of thermophilic proteins for the development of a new class of fluorescence non-consuming substrate biosensors for monitoring the levels of two analytes of high social interest, such as glucose and sodium.
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Affiliation(s)
| | | | | | - Sabato D'Auria
- Institute of Protein Biochemistry, CNR, Italian National Research CouncilVia Pietro Castellino, 111, 80131 Naples, Italy
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Stein EW, Grant PS, Zhu H, McShane MJ. Microscale enzymatic optical biosensors using mass transport limiting nanofilms. 1. Fabrication and characterization using glucose as a model analyte. Anal Chem 2007; 79:1339-48. [PMID: 17297932 PMCID: PMC2518633 DOI: 10.1021/ac061414z] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
"Smart tattoo" sensors-fluorescent microspheres that can be implanted intradermally and interrogated noninvasively using light-are being developed as potential tools for in vivo biochemical monitoring. In this work, a platform for enzymatic tattoo-type sensors is described and prototype devices evaluated using glucose as a model analyte. Sensor particles were prepared by immobilizing Pt(II) octaethylporphine (PtOEP), a phosphorescent dye readily quenched by molecular oxygen, into hybrid silicate microspheres, followed by loading and subsequent covalent immobilization of glucose oxidase. Rhodamine B-doped multilayer nanofilms were subsequently assembled on the surfaces of the particles to provide a reference signal and provide critical control of glucose transport into the particle. The enzymatic oxidation of glucose within the sensor results in the glucose concentration-dependent depletion of local oxygen levels, enabling indirect monitoring of glucose by measuring relative changes in PtOEP emission. A custom testing apparatus was used to monitor the dynamic sensor response to varying bulk oxygen and glucose levels, respectively. For the prototypes tested, dynamic test results indicate that the sensors respond rapidly (t(95) = 84 s) and reversibly to changes in bulk glucose levels, while demonstrating high baseline stability. The sensitivity (change in intensity ratio) of these devices was determined to be 4.16 +/- 0.57%/mg dL(-1). The analytical range for the prototypes was determined to be 2-120 mg/dl, though this can be extended to cover the physiologically relevant range by tailoring the nanofilm coatings. These findings confirm the potential for enzymatic microscale optical and pave the way for extension of this initial demonstration with glucose to target other biochemical species relevant to metabolic monitoring.
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Affiliation(s)
- Erich W. Stein
- Biomedical Engineering Program, Louisiana Tech University, Ruston, Louisiana 71272
- The Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272
| | - Patrick S. Grant
- The Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272
| | - Huiguang Zhu
- The Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272
| | - Michael J. McShane
- Biomedical Engineering Program, Louisiana Tech University, Ruston, Louisiana 71272
- The Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana 71272
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843
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Affiliation(s)
- Raz Jelinek
- Department of Chemistry and Staedler Minerva Center for Mesoscopic Macromolecular Engineering, Ben Gurion University of the Negev, Beersheva 84105, Israel.
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Pickup JC, Hussain F, Evans ND, Rolinski OJ, Birch DJS. Fluorescence-based glucose sensors. Biosens Bioelectron 2005; 20:2555-65. [PMID: 15854825 DOI: 10.1016/j.bios.2004.10.002] [Citation(s) in RCA: 337] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Revised: 10/06/2004] [Accepted: 10/06/2004] [Indexed: 12/31/2022]
Abstract
There is an urgent need to develop technology for continuous in vivo glucose monitoring in subjects with diabetes mellitus. Problems with existing devices based on electrochemistry have encouraged alternative approaches to glucose sensing in recent years, and those based on fluorescence intensity and lifetime have special advantages, including sensitivity and the potential for non-invasive measurement when near-infrared light is used. Several receptors have been employed to detect glucose in fluorescence sensors, and these include the lectin concanavalin A (Con A), enzymes such as glucose oxidase, glucose dehydrogenase and hexokinase/glucokinase, bacterial glucose-binding protein, and boronic acid derivatives (which bind the diols of sugars). Techniques include measuring changes in fluorescence resonance energy transfer (FRET) between a fluorescent donor and an acceptor either within a protein which undergoes glucose-induced changes in conformation or because of competitive displacement; measurement of glucose-induced changes in intrinsic fluorescence of enzymes (e.g. due to tryptophan residues in hexokinase) or extrinsic fluorophores (e.g. using environmentally sensitive fluorophores to signal protein conformation). Non-invasive glucose monitoring can be accomplished by measurement of cell autofluorescence due to NAD(P)H, and fluorescent markers of mitochondrial metabolism can signal changes in extracellular glucose concentration. Here we review the principles of operation, context and current status of the various approaches to fluorescence-based glucose sensing.
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Affiliation(s)
- John C Pickup
- Department of Chemical Pathology, Guy's, King's and St Thomas's School of Medicine, Guy's Hospital, London SE1 9RT, UK.
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Hussain F, Birch DJS, Pickup JC. Glucose sensing based on the intrinsic fluorescence of sol-gel immobilized yeast hexokinase. Anal Biochem 2005; 339:137-43. [PMID: 15766720 DOI: 10.1016/j.ab.2005.01.016] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2004] [Indexed: 11/20/2022]
Abstract
In this study, we investigated measurements of the intrinsic fluorescence of yeast hexokinase as an assay for glucose and immobilization of the enzyme in a silica sol-gel matrix as a potential in vivo glucose sensor for use in patients with diabetes. The intrinsic fluorescence of hexokinase in solution (excitation=295 nm, emission=330 nm) decreased by 23% at a saturating glucose concentration of 1 mM (Kd=0.3 mM), but serum abolished the glucose-related fluorescence response. When entrapped in tetramethylorthosilicate-derived sol gel, hexokinase retained activity, with a 25% maximal glucose-related decrease in intrinsic fluorescence, and the saturation point was increased to 50 mM glucose (Kd=12.5 mM). The glucose response range was increased further (to 120 mM, Kd=57 mM) by a covering membrane of poly(2-hydroxyethyl) methacrylate. Unlike free enzyme, the fluorescence responses to glucose with sol-gel immobilized hexokinase, with or without covering membrane, were similar for buffer and serum. We conclude that fluorescence monitoring of sol-gel entrapped yeast hexokinase is a suitable system for development as an in vivo glucose biosensor.
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Affiliation(s)
- Faeiza Hussain
- Department of Chemical Pathology, Guy's, King's, and St. Thomas's School of Medicine, Guy's Hospital, London SE1 9RT, UK
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Sanz V, de Marcos S, Castillo JR, Galbán J. Application of Molecular Absorption Properties of Horseradish Peroxidase for Self-Indicating Enzymatic Interactions and Analytical Methods. J Am Chem Soc 2005; 127:1038-48. [PMID: 15656642 DOI: 10.1021/ja046830k] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this paper an in depth study is presented of the use of the horseradish peroxidase (HRP) enzyme as a self-indicating biorecognition reagent in UV-vis molecular absorption spectrometry. The HRP/H2O2 reaction mechanism in the absence of an external substrate has been clarified, and the interaction between HRP and glucose oxidase (GOx) has been studied. It has been demonstrated that GOx can act as a substrate of HRP; in both cases the kinetic constants have been obtained and mathematical models have been developed. Second, the HRP/H2O2 reaction is used to follow a H2O2-producing enzymatic reaction, the glucose reaction with GOx being used as a model. As an application of this, two methodologies have been proposed for glucose determination: with or without previous incubation of glucose with GOx. In both cases mathematical models relating HRP absorbance changes to glucose concentration have been developed and tested; both methods have been optimized, analytically characterized, and tested for glucose determination in samples. The methodology described could be applied to other heme-proteins and to other H2O2-producing enzymatic reactions. The models permit the reaction constants to be calculated. From the analytical chemistry point of view the models allow the prediction of the method sensitivity for other analytes involved in this type of reaction if the kinetic constants are known and can be used in the design of optical sensors.
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Affiliation(s)
- Vanesa Sanz
- GEAS, Analytical Chemistry Department, Faculty of Sciences, University of Zaragoza, Zaragoza-50009, Spain
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Staiano M, Bazzicalupo P, Rossi M, D'Auria S. Glucose biosensors as models for the development of advanced protein-based biosensors. MOLECULAR BIOSYSTEMS 2005; 1:354-62. [PMID: 16881003 DOI: 10.1039/b513385h] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Glucose sensing is used as a model to explore the advantages and problems deriving from the use of either enzymes or sugar binding proteins to develop stable fluorescence biosensors. We report on a novel approach to address the problem of substrate consumption by sensors based on enzymes, namely the utilization of apo-enzymes as non-active forms of the protein which are still able to bind the substrate/ligand. We also review studies in which derivatization of a naturally thermostable sugar-binding protein with a fluorescent probe allows quantitative monitoring of glucose binding even after immobilization on a solid support.
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Affiliation(s)
- Maria Staiano
- Institute of Protein Biochemistry, CNR, Italian National Research Council, Via Pietro Castellino, Naples, Italy
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Liang F, Pan T, Sevick-Muraca EM. Measurements of FRET in a Glucose-sensitive Affinity System with Frequency-domain Lifetime Spectroscopy. Photochem Photobiol 2005; 81:1386-94. [PMID: 16120004 DOI: 10.1562/2005-02-14-ra-440] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We report measurements of fluorescence resonance energy transfer (FRET) for glucose sensing in an established concanavalin A-dextran affinity system using frequency-domain lifetime spectroscopy. A dextran (MW 2,000,000) labeled with a small fluorescent donor molecule, Alexa Fluor 568, was used to competitively bind to a sugar-binding protein, concanavalin A, labeled with acceptor molecule, Alexa Fluor 647, in the presence of glucose. The FRET-quenching kinetics of the donor were analyzed from frequency-domain measurements as a function of both glucose and acceptor-protein concentrations using a Förster-type decay kinetics model. The results show that the frequency-domain measurements and donor decay kinetics can quantitatively indicate changes in the competitive binding of 0.09 microM dextran to labeled concanavalin A at a solution concentration of 10.67 microM in the presence of glucose at concentrations ranging from 0 to 224 mg/dL.
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Affiliation(s)
- Feng Liang
- The Photon Migration Laboratory, Department of Chemistry, Texas A&M University, College Station, USA
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Ye K, Schultz JS. Genetic Engineering of an Allosterically Based Glucose Indicator Protein for Continuous Glucose Monitoring by Fluorescence Resonance Energy Transfer. Anal Chem 2003; 75:3451-9. [PMID: 14570197 DOI: 10.1021/ac034022q] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Real-time monitoring of blood glucose could vastly reduce a number of the long-term complications associated with diabetes. In this article, we present a novel approach that relies on a glucose-binding protein engineered such that a 20% reduction in fluorescence due to the fluorescence resonance energy transfer occurs as a result of glucose binding. This change in fluorescence provides a signal for the optical detection of glucose. The novel glucose indicator protein (GIP) was created by fusing two fluorescent reporter proteins (green fluorescent proteins) to each end of an Escherichia coli glucose-binding protein in such a manner that the spatial separation between the fluorescent moieties changes when glucose binds, thus generating a distinct optical signal that can be used for glucose detection. By placing the GIP within a dialysis hollow fiber sensor, a microsensor has been developed for continuous monitoring of glucose. The sensor had a response time to sudden glucose changes within 100 s and was reversible. The sensor was shown to have an optional range on the order of 10 microM of glucose.
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Affiliation(s)
- Kaiming Ye
- Center for Biotechnology and Bioengineering, University of Pittsburgh, 300 Technology Drive, Pittsburgh, Pennsylvania 15219, USA.
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