Portable Health Lab ( Glucowatch )

1. Portable Health Lab(Glucowatch) Final Year Project Unfinished portion EngrMuzzamilJavaid

2. Cygnus Inc. • GlucoWatch was launched in early 2002 by Cygnus Inc., a non-invasive glucose monitoring device. • We tried to add this amazing technology in our Final Year Project, but due to unavailability of its components from local markets we were unable to continue this dream, and this portion of our Portable Health Lab remained unfinished. • I gathered information from different sites and made this presentation. • Its sole purpose is to share this little information, that I was able to get, with those who want to learn.

3. BIOSENSOR

4. Main parts of a biosensor • the biological recognition elements that differentiate the target molecules in the presence of various chemical. • a transducer that converts the biorecognitionevent into a measurable signal. • a signal processing system that converts the signal into a readable value.

5. Biorecognition elements • Receptors • enzymes • Antibodies • nucleic acids • Microorganisms • lectins

6. Transducers • Electrochemical • Optical • Thermometric • Piezoelectric • Magnetic

7. Signal Processing System: • Microcontroller

8. Electrochemical transducers • Potentiometric • Amperometric • conductometric

9. Enzymes • Hexokinase • Glucose oxidase (GOx) • glucose-1-dehydrogenase (GDH)

10. Why Gox? • GOx is the standard enzyme for biosensors • GOxis easy to obtain • Cheap • Can withstand greater extremes of pH, ionic strength, and temperature than many other enzymes

11. Enzymaticamperometricglucosebiosensors

12. Basic Concept

13. The basic concept of the glucose biosensor is based on the fact that the immobilized GOxcatalyzes the oxidation of β-D-glucose by molecular oxygenproducing gluconic acid and hydrogen peroxide . In order to work as a catalyst, GOx requires a redox cofactor—flavin adenine dinucleotide (FAD). FAD works as the initial electron acceptor and is reduced to FADH2. Glucose + GOx– FADGlucolactone+ GOx – FADH2

14. The cofactor is regenerated by reacting with oxygen, leading to the formation of hydrogen peroxides. Gox–FADH2 + O2 Gox– FAD + H2O2

15. Hydrogen peroxide is oxidized at a catalytic, classically platinum (Pt) anode. H2O2 + 2H(+) O2 + 2e(-) The electrode easily recognizes the number of electron transfers, and this electron flow is proportional to the number of glucose molecules present.

16. Biosensors components Three electrodes: • Iontophoresis electrode (silver-silverchloride) • Working electrode (platinum) • Reference electrode

17. Glucowatch

18. Working • 20 Minutes cycle First half 10 minutes Second Half 10 minutes

19. First Half Cycle 10 minutes • Cycle starts as the sensor's silver-silverchlorideiontophoresis electrode applies a 300-microamp current to the skin • For the next three minutes, positive and negative ions travel through the patient's skin to GlucoWatch's side-by-side collection discs, which serve as an anode and cathode during glucose extraction.

20. This ion migration brings glucose along for the ride, depositing it at the cathode.

21. Next, enzymes in a cathode disc chemically break down the glucose, producing ananoamp-sized electrochemical signal that the device's platinum biosensing electrode measures over a seven-minute period. Glucose + GOx –FADGlucolactone + GOx – FADH2 Gox–FADH2 + O2 Gox– FAD + H2O2 H2O2 + 2H(+) O2 + 2e(-) Glucose  2e(-)

22. Second half cycle • For the next ten minutes of the cycle, the GlucoWatch repeats the same steps but with the sensor's polarity reversed. This way, the disc that acted as the anode in the first half of the cycle becomes the cathode in the second, in order to prevent the plating that would otherwise shorten sensor life.

23. Final Reading The final glucose reading displayed by the GlucoWatchaverages the two ten-minute cycles.