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  1. Biosensor Boot Camppart 2 David E Williams

  2. Title: ELECTRODE SYSTEMS FOR CONTINUOUS MONITORING IN CARDIOVASCULAR SURGERY Author(s): CLARK, LC; LYONS, C Source: ANNALS OF THE NEW YORK ACADEMY OF SCIENCES Volume: 102 Issue: 1 Pages: 29-& DOI: 10.1111/j.1749-6632.1962.tb13623.x Published: 1962 Times Cited: 1,093 (from Web of Science Glucose oxidase-containing membrane

  3. Gox-containing membrane Ag anode Pt cathode oxygen glucose Signal decreases as glucose increases in this configuration

  4. In 1970, Dr. Clark demonstrated the enzyme-activated polarographic measurement of glucose in water and pointed out that glucose could be measured in whole blood with the presence of the glucose oxidase enzyme. Within a couple of years, YSI was able to market its pioneering Model 23 Glucose Analyzer with a polarographic electrode. This model was the first whole-blood glucose analyzer. The instrument directly measures the whole-blood glucose level from a 25-microliter sample within a ±2% accuracy. The sensor created for the Model 23A was the first commercial biosensor and was used in the Miles Biostator, the first artificial pancreas. The U.S. Food and Drug Administration has identified the YSI Model 23A and subsequent designs as the reference standard for measuring glucose. http://www.ysi.com/history.php http://www.chemheritage.org/discover/collections/collection-items/scientific-instruments/ysi-blood-glucose-analyzer-model-23a.aspx

  5. Hydrogen peroxide readily depolarizes the polarographicanode and current flow, at a given applied voltage (usually about 0.9 volt), is proportional to the hydrogen peroxide concentration. If glucose were to be measured in blood by mixing the enzyme and the blood, no glucose would be detected because blood contains the enzyme, catalase, which destroys hydrogen peroxide at a very fast rate. This difficulty, and others, are circumvented through the use of a cellulose or other membrane which is permeable to small molecules, such as glucose, but is impermeable to proteins. The membrane serves to keep the glucose oxidase on the side of the membrane with the anode and at the same time to keep other enzymes, some of which, such as catalase, would ruin the reaction, on the other side of the membrane. Glucose has a molecular weight of 180 and can freely diffuse through the membrane. The product of the reaction, hydrogen peroxide, has a low molecular weight, only 34, but by virtue of the design of the present invention is formed directly on the platinum electrode surface where it is detected, and in the process of being detected is, in part at least converted to H20 and oxygen. Ag/AgCl cathode Pt anode: H2O2 oxidation

  6. In 1970, Dr. Clark demonstrated the enzyme-activated polarographic measurement of glucose in water and pointed out that glucose could be measured in whole blood with the presence of the glucose oxidase enzyme. Within a couple of years, YSI was able to market its pioneering Model 23 Glucose Analyzer with a polarographic electrode. http://www.chemheritage.org/discover/collections/collection-items/scientific-instruments/ysi-blood-glucose-analyzer-model-23a.aspx This model was the first whole-blood glucose analyzer. The instrument directly measures the whole-blood glucose level from a 25-microliter sample within a ±2% accuracy. The sensor created for the Model 23A was the first commercial biosensor and was used in the Miles Biostator, the first artificial pancreas. The U.S. Food and Drug Administration has identified the YSI Model 23A and subsequent designs as the reference standard for measuring glucose. http://www.ysi.com/history.php

  7. Think a bit… the assumptions connecting the measurement to the desired quantity In the space: Glucose + O2 -> H2O2 At the electrode: H2O2 -> O2 Glucose conc Current ~ gradient of H2O2 at electrode Oxygen conc concentration Small gap underneath membrane relative to membrane thickness Gap is controlled – another membrane Large excess of Gox – fast reaction H2O2conc position

  8. Home use glucose

  9. Development of the home-use glucose sensor Ferrocene-Mediated Enzyme Electrode for Amperometric Determination of Glucose Anthony E. G. Cass,’ Graham Davis, Graeme D. Francis, and H. Allen 0. Hill* Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, United Kingdom William J. Aston, I. John Higgins, Elliot V. Plotkin, Lesley D. L. Scott, and Anthony P. F. Turner Biotechnology Centre, Cranfield Institute of Technology, Bedford MK43 OAL, United Kingdom Anal. Chem., 1984, 56 (4), pp 667–671 Removes oxygen dependence Eliminates uric acid and ascorbate interference Concept for a single use, batch calibrated device Fc + glucose + GOx Fc or Fc + glucose or Fc + GOx

  10. glucose + M(ox) gluconolactone+ M(red) Fc Fc+ GOx the reaction : Fc+ + glucose + GOx regenerates Fc near the electrode so current doesn’t decrease Fc → Fc+ + e- anodic current decreases when Fc is depleted near the electrode for glucose measurement, hold potential constant at ~ 0.4 V and measure current

  11. The reaction of Fc+ and GOx(red): a classic ErCi’ system E = electrochemical step C’ = homogeneous catalytic chemical reaction r = reversible i = irreversible Examples of some other classic mechanisms: ErCr ErCiEr CrEi (C = homogeneous chemical reaction)

  12. bulk concentrations, i.e. what’s added at the start Fc/GOx system R (Fc) O (Fc+)+ e O (Fc+) + Z (glucose) R + Y (gluconolactone) k’ A.J. Bard, L.R. Faulkner, Electrochemical Methods: Fundamentals and Applications, ed. John Wiley: New York, 2001; Chapter 12.

  13. Reaction consumes ‘O’ and regenerates ‘R’ in the boundary layer near the electrode as ‘O’ is produced at the electrode R (Fc) O (Fc+)+ e O (Fc+) + Z (glucose) R + Y (gluconolactone) k’

  14. Technology and market drivers • Lower blood volume • More precision • Avoiding other peoples’ patents • -> coulometers • -> high concentration solutions of enzyme and mediator • -> old (ferrocyanide) and new (osmium) mediators

  15. Chamber of precisely known volume, capillary fill Dried reagents give high concentration solutions Complete conversion of glucose in sample to gluconolactone with equivalent reduction of ferricyanide Coulometric determination of amount of ferrocyanide produced Precision determined by precision of manufacture of the defined sample volume

  16. Lifescan ‘one-touch’ reagents spacer 100um gap Electrodes in chamber ~1uL sample volume; 5s measurement; made by web printing process : 106 / hr

  17. http://ubimon.doc.ic.ac.uk/bsn/public/bsn-2005-Heller.pdf Therasense : Adam Heller Glucose  gluconolactone GoX Os(III)  Os(II)

  18. http://ubimon.doc.ic.ac.uk/bsn/public/bsn-2005-Heller.pdf

  19. http://www.boots.com/en/Pharmacy-Health/Health-shop/Diagnostics-electrical-health/Blood-glucose-monitors/http://www.boots.com/en/Pharmacy-Health/Health-shop/Diagnostics-electrical-health/Blood-glucose-monitors/

  20. Random Thoughts list • Strep – antigen extraction • Glucose – how devices changed and the assumptions behind operation • Flow injection, protective membranes, Bourtelle and Albery, one shot • Microfluidics • Surfaces and interactions • Immunoassay theory

  21. Freckmannet al.“System Accuracy Evaluation of 27 Blood Glucose Monitoring Systems According to DIN EN ISO 15197”. Diabetes Technol. Ther. 2010, 12. 221-231, DOI: 10.1089/dia.2009.0128