Compensation of Temperature and Concanavalin A Concentratration Effects for Glucose Determination by the Viscometric Affinity Assay

Beyer, Uwe; Ehwald, R.

doi:10.1021/bp000119b

Cited by 17 publications

(12 citation statements)

References 8 publications

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“…ConA has been successfully used in a viscomechanical glucose-sensing device in vivo, 19,20 and it has been employed in various optical sensors measuring fluorescence changes in vitro that correlated with glucose concentrations. 18,[21][22][23][24][25][26][27][28][29][30][31] Schultz and co-workers introduced the scheme of a minimally invasive fluorescence microdialysis sensor residing in skin tissue only a few millimeters underneath the dermis.…”

Section: Military Metabolic Monitoringmentioning

confidence: 99%

Fluorescence Resonance Energy Transfer-Based Near-Infrared Fluorescence Sensor for Glucose Monitoring

Ballerstädt

Gowda

McNichols

2004

Diabetes Technology & Therapeutics

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A novel near-infrared (NIR) fluorescence affinity sensor for continuous glucose monitoring was developed and characterized. The sensor operates by fluorescence resonance energy transfer between a NIR chromophore linked to concanavalin A (ConA) and an NIR fluorophore linked to free dextran. The binding of dextran with ConA in the absence of glucose results in low fluorescence due to quenching; however, the quenching is reversed by competitive displacement of dextran from ConA by glucose. In order to increase thermodynamic stability and the lifetime of the sensor, ConA was immobilized within a macroporous bead matrix. The sensor was contained within a sealed hollow dialysis fiber (o.d. 215 microm, wall thickness 20 microm), preventing the macromolecules from leaking out and enabling glucose to rapidly enter the fiber lumen. A glucose-insensitive reference fluorophore was also incorporated to allow for ratiometric measurements, resulting in a robust sensor output that is independent of positional and/or light intensity changes. The response of the fluorescence affinity sensor to glucose was tested continuously in an automated test chamber at 37 degrees C. The sensor showed good dynamic range within physiologically relevant glucose concentration range (15% change over 2.5-30 mM, no hysteresis), fast response time (2-4 min), and a remarkable long-term stability (6 months). We interpret the improved longevity of this sensor to be the result of an optimized photo exposure regime and immobilization of ConA to the matrix. Its small size, ratiometric output, and NIR fluorescence make this sensor well suited for dermal implantation and continuous transdermal monitoring.

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Section: Military Metabolic Monitoringmentioning

confidence: 99%

Fluorescence Resonance Energy Transfer-Based Near-Infrared Fluorescence Sensor for Glucose Monitoring

Ballerstädt

Gowda

McNichols

2004

Diabetes Technology & Therapeutics

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“…It should be emphasised that the concept of the relative fluidity [31] has been straightforward for the design of the VAS, as it facilitates calibration and reduces the undesired influence of variations in temperature, air pressure, flow rate and polymer concentrations, all of which strongly affect the absolute measure of viscosity.…”

Section: Discussionmentioning

confidence: 99%

“…The relative fluidity (F r ) of the sensitive liquid, which shows a linear dependence on the glucose concentration C [31], is obtained from the signals given by pressure transducer 1 (p 1 ) and pressure transducer 2 (p m ) by:…”

Section: Methodsmentioning

confidence: 99%

“…Saturating concentrations of free glucose reduce this viscosity by more than one order of magnitude [28]. By using a suitable reference measurement, the viscometric glucose assay is insensitive to variations in measuring conditions such as temperature and polymer concentration [31]. Although different concepts of viscometric sensors have been developed [29, 32±33], applicable miniaturised prototypes for continuous measurement in the subcutaneous tissue have not been available before.…”

Section: : 416±423]mentioning

confidence: 99%

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Recording of subcutaneous glucose dynamics by a viscometric affinity sensor

Beyer¹,

Schafer²,

Thomas³

et al. 2001

Diabetologia

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Portable glucose sensors with an accurate and longterm stable in vivo function have been in demand for several decades because such devices are of strategic importance in the diagnosis and treatment of diabetes mellitus [1±3]. Despite remarkable progress, the development of new and improvement of existing prototypes is desirable.Efforts have focused on transdermal glucose sensors because the glucose concentrations of capillary blood and interstitial liquid of the subcutaneous tissue are closely related [4±8]. These sensors measure the glucose concentration either after electroosmotic transfer of the interstitial liquid to the skin surface [9] or by a microsensor implanted into the subcutaneous tissue. Most work has been carried out using needle-like transdermal amperometric sensors with immobilised glucose oxidase (GOD) [10±18]. To render the highly sensitive and oxygen-dependent enzyme reaction glucose-limited, the immobilised enzyme is usually covered by a membrane that is less Diabetologia (2001) Abstract Aims/hypothesis. To provide a nonenzymatic sensor for glucose monitoring in subcutaneous tissue. Methods. A continuously working affinity sensor based on the glucose-dependent viscosity of a sensitive liquid containing dextran and concanavalin A has been designed by arranging a microdialysis probe, two flow-resisting capillaries and two pressure transducers in a linear flow system. It allows synchronous processing of the viscosity of the sensitive liquid at the standard glucose concentration and the glucose concentration to be measured. In preliminary human trials the sensor was implanted into the subcutaneous tissue of the forearm and its read-out was compared with capillary blood concentrations.Results. In vitro, the viscometric sensor shows a linear and long-term stable dependence on the glucose concentration without detectable drift. At the applied flow rate of the sensitive liquid (about 5 ml/h) the technical delay is 5 to 10 min. The read-out of the implanted sensor followed the dynamics of the capillary blood glucose concentrations with a time-shift of 10 to 15 min but showed a systematic error when based on precalibration with polymer-free glucose solutions. After appropriate in vivo calibration, the readout was in good or acceptable coincidence with capillary blood concentrations according to the error grid method and did not show any detectable reduction of sensitivity during the periods of measurement (up to 44 h). Conclusion/interpretion. The viscometric-affinity sensor is an efficient tool for current research on glucose monitoring in the subcutaneous tissue and can potentially be further developed for routine clinical use.[ Diabetologia (2001) 44: 416±423]

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“…In case of sensitive liquids making use of aqueous solutions out of high molecular, polyvalent dextran and the tetravalent glucose receptor ConA, free glucose reduces the cross-links by ConA between the dextran molecules in the aqueous solution and decreases viscosity. 10,[28][29][30] A CGM system based on such a sensor with continuous pressure measurement on fluidic resistances was tested in clinical trials. 31,32 More recently MEMS-based viscometric sensors were developed with optical or capacitive signal transduction, 33 some of them making use of synthetic glucose receptors with phenyl boronic acids.…”

mentioning

confidence: 99%

Glucose Measurement by Affinity Sensor and Pulsed Measurements of Fluidic Resistances

Beyer¹,

Wyss²,

Robin³

et al. 2014

J Diabetes Sci Technol

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Continuous glucose monitoring (CGM) of changes in the glucose levels in the interstitial fluid (ISF) in the subcutaneous tissue is a diagnostic option that allows patients with diabetes to optimize their metabolic control. 1,2 Over the past decade, different types of needle sensors from 3 manufacturers became commercially available: Medtronic (Northridge, CA), 3 Abbott Diabetes Care (Alameda, CA), 4 and DexCom (San Diego, CA). 5 The amperometric enzymatic measuring principle allows all these CGM systems to measure the rate of glucose consumption by an enzyme. This measurement principle depends on the rate of glucose flow from the ISF to the enzyme immobilized on the sensor surface through membranes covering the sensor. A stable sensor signal requires a constant diffusion rate of glucose; this however usually is not the case in situ as biofouling of the membrane takes place. This not well-defined process includes the deposition of cells or proteins to the sensor surface that become additional barriers hampering glucose diffusion. This causes signal drift and changes in the intensity of the sensor raw signal within days. To overcome such shortcomings, glucose sensors were developed that couple the amperometric measurement with the micro-dialysis principle. The latter allows generation of a fluid with a glucose concentration that is closely correlated to that in the ISF but which is practically protein-free. The glucose signals generated by such systems were accurate and stable over time. 6,7 To date, only one microdialysis system (GlucoDay; Menarini, Florence, Italy) is available on the market in Europe. 8 This is mainly used for research purposes. Affinity sensors employ a different measuring principle; these are based on the reversible binding of the analyte to a specific receptor. In the case of glucose, the protein 6957D STXXX10.

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Compensation of Temperature and Concanavalin A Concentratration Effects for Glucose Determination by the Viscometric Affinity Assay

Cited by 17 publications

References 8 publications

Fluorescence Resonance Energy Transfer-Based Near-Infrared Fluorescence Sensor for Glucose Monitoring

Fluorescence Resonance Energy Transfer-Based Near-Infrared Fluorescence Sensor for Glucose Monitoring

Recording of subcutaneous glucose dynamics by a viscometric affinity sensor

Glucose Measurement by Affinity Sensor and Pulsed Measurements of Fluidic Resistances

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