Glucose sensor

GLUCOSE SENSOR

1. Glucose Sensors Supervised by: Dr. Satyabrata Mohapatra Assistant Professor of Nanoscience & Technology School of Basic and Applied Sciences Room No. 201, Block - B, Guru Gobind Singh Indraprastha University Made by: Nikita Gupta Enrollment no-01140801014 Mtech-NST(1 st Sem)

2. Block diagram of biosensor A biosensor is an analytical device which is used to determine the presence and concentration of a specific substance in a biological analyte Biosensor Display Bioreceptor Transducer Signal Processing Desired molecule Introduction to Biosensors Biosample

3. Basic characteristics of a biosensor LINEARITY: Maximum linear value of the sensor calibration curve. Linearity of the sensor must be high for the detection of high substrate concentration. SENSITIVITY : The value of the electrode response per substrate concentration. SELECTIVITY : Interference of chemicals must be minimized for obtaining the correct result. RESPONSE TIME: The necessary time for having 95% of the response.

4. Introduction to Biosensors Bioreceptor Transducer Antibody Enzyme Nucleic Acid (DNA) Cell MIP Optical Electrochemical Mass based Temperature based potentiometric amperometric conductimetric Electric & Magnetic Dielectric properties Permeability properties Voltage or Current Fluorescence Interference Absorption

5. Applications of biosensors Glucose monitoring in diabetes patients  ←historical market driver Environmental applications e.g. the detection of pesticides and river water contaminants such as heavy metal ions . Remote sensing of airborne bacteria e.g. in counter-bioterrorist activities Detection of pathogens . Determining levels of toxic substances before and after bioremediation Detection and determining of organophosphate Routine analytical measurement of folic acid, biotin, vitamin B12 and pantothenic acid as an alternative to microbiological assay Determination of drug residues in food, such as antibiotics and growth promoters, particularly meat and honey. Drug discovery and evaluation of biological activity of new compounds. Protein engineering in biosensors Detection of toxic metabolites such as mycotoxins

6. Amperometric biosenor Amperometric biosensors are self-contained integrated devices based on the measurement of the current resulting from the oxidation or reduction of an electroactive biological element providing specific quantitative analytical information .

7. Blood Glucose Monitoring What is it? Blood Glucose Monitoring is a way of checking the concentration of glucose in the blood using a glucometer. What is the purpose? Provides quick response to tell if the sugar is high or low indicating a change in diet, exercise or insulin. Over time, it reveals individual of blood glucose changes.

8. Why monitor blood glucose? Reduces risk of developing complications with diabetes. Allows diabetics to see if the insulin and other medications they are taking are working. Gives diabetics an idea as to how exercise and food affect their blood sugar. May prevent hypoglycemia or hyperglycemia

9. Amperometric Glucose Biosensor Developed by Updike and Hicks Enzyme Glucose oxidase catalyze the oxidation of glucose by molecular oxygen producing glucolactone and hydrogen peroxide. In order to work as a catalyst, GOx requires a redox cofactor – flavin adenine dinucleotide (FAD), works as an initial electron acceptor and is reduced to FADH 2 . Glucose + GOx –FAD + Glucolactone + GOx – FADH 2

10. The cofactor is regenerated by reacting with oxygen, leading to the formation of hydrogen peroxide GOx – FADH 2 + O 2 GOx – FAD + H 2 O 2 Hydrogen peroxide is oxidized at a platinum electrode. The number of electron transfers, at electrode surface is directly proportional to the number of glucose molecules present in the blood. H 2 O 2 2H + +O 2 + 2 e - Three strategies used for the electrochemical sensing of glucose are By measuring oxygen consumption By measuring the amount of hydrogen peroxide produced by the enzyme reaction By using a diffusible or immobilized mediator to transfer the electrons from Gox to the electrode.

11. Types of glucose biosensors

12. Generations 1 st generation: the normal product of the reaction diffuses to the transducer and causes electrical response 2 nd generation : involves specific mediators between reaction and transducer to generate improved response 3 rd generation: reaction itself causes the response

13. First generation glucose biosensors The first generation glucose biosensors estimated glucose concentration in the sample based on hydrogen peroxide production by glucose oxidase utlizing dissolved oxygen. Based on this technology, Yellow spring Instrument company, launched the first commercial glucose biosensor in market in 1975 for the direct measurement of glucose. The usage of the most expensive metal platinum for the fabrication of this electrode restricted the biosensor to clinical laboratories only.

14. Major drawbacks of first generation glucose biosensors Amperometric measurement of hydrogen peroxide required a high operating potential (0.6 V) for high selectivity. Restricted solubility of oxygen in biological fluids, which produced fluctuations in the oxygen tension. Deactivation of the enzyme due to the production of hydrogen peroxide.

15. Second generation glucose biosensor The second generation glucose biosensor utilized redox mediator to transfer electrons from the enzyme to the working electrode surface. A variety of redox mediators, such as ferrocene , ferricyanide , quinines, methylene blue etc were used to improve sensor performance. Usage of redox mediator eliminated the need of oxygen for electron transfer at the electrode surface, thus overcoming the drawback of limited oxygen pressure observed in the first generation biosensor. The lower redox potential of chosen mediators (0-2 V) results in no interference from other electroactive species such as uric acid, ascorbic acid. Redox mediator enhances the electron transfer between the redox center of enzyme and the electrode surface.

16. Major drawbacks of second generation glucose biosensors High competition between redox mediator and oxygen. Interference of other electroactive species lead to false and inaccurate results. Small size and highly diffusive nature of mediators poses problem of leaching of mediator from intermediate region between enzyme and electrode surface.

17. Third generation glucose biosensors The third generation glucose biosensors are based on the direct electron transfer between the active center of enzyme and the electrode. The intrinsic barrier to electron flow is the globular structure of glucose oxidase with the active site, containing FAD/FADH 2 redox cofactor, buried deep inside a cavity of ~ 13 A ◦ is a major hinderance for direct electron transfer. Carbon nanotubes immobilized electrode surface provide suitable orientation for enzyme immobilization and establish connection between electrode surface and deeply buried active site of enzyme.

18. Non-enzymatic glucose biosensors The use of non-enzymatic electrodes as glucose sensors potentially promises a fourth generation to analytical glucose oxidation. The active metal nanoparticle undergo a oxidation step that forms a hydrous oxide layer OH ads that mediate oxidation of the adsorbed species.

19. Glucose Biosensors Based on Carbon Nanotube Nano electrode Ensembles T he development of glucose biosensors based on carbon nanotube (CNT) Nano electrode ensembles (NEEs) for the selective detection of glucose. CNTs have a high electrocatalytic effect and a fast electron-transfer rate. Glucose oxidase was covalently immobilized on CNT NEEs via carbodiimide chemistry by forming amide linkages between their amine residues and carboxylic acid groups on the CNT tips. The catalytic reduction of hydrogen peroxide liberated from the enzymatic reaction of glucose oxidase upon the glucose and oxygen on CNT NEEs leads to the selective detection of glucose. The biosensor effectively performs a selective electrochemical analysis of glucose in the presence of common interferents (e.g., acetaminophen, uric and ascorbic acids), avoiding the generation of an overlapping signal from such interferers. Such an operation eliminates the need for permselective membrane barriers or artificial electron mediators, thus greatly simplifying the sensor design and fabrication.

20. The fabrication of glucose biosensors based on CNT NEEs for the selective and sensitive detection of glucose. CNT NEEs eliminate potential interference through the preferential detection of hydrogen peroxide. Such development of interference-free transducers should simplify the design and fabrication of conventional and miniaturized sensing probes. The glucose biosensor based on an aligned CNT NEE is thus suitable for the highly selective detection of glucose in a variety of biological fluids (e.g., saliva, sweat, urine, and serum). The biosensor fabrication technology demonstrated in this work is readily applicable to the fabrication of other biosensors based on oxidases, such as biosensors for cholesterol, alcohol, lactate, acetylcholine, choline, hypox - anthine , and xanthine.

21. Glucose biosensor test strips Meter Read glucose Dry coating of GO + Fc Patient adds drop of blood, then inserts slide into meter I t Patient reads glucose level on meter e’s electrodes

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