The document summarizes the key components and characteristics of biosensors, with a focus on glucose biosensors. It describes: 1) The basic components of a biosensor including the bioreceptor, transducer, and signal processing. 2) The characteristics of biosensors such as linearity, sensitivity, and selectivity. 3) The different generations of glucose biosensors, including first generation using oxygen, second generation using redox mediators, and third generation with direct electron transfer. 4) Applications of glucose biosensors based on carbon nanotube nano electrode ensembles which can selectively detect glucose without interference.

1. 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(1st 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
DisplayBioreceptor 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 FADH2.
Glucose + GOx –FAD+ Glucolactone + GOx – FADH2

10. • The cofactor is regenerated by reacting with oxygen, leading to the
formation of hydrogen peroxide
GOx – FADH2 + O2 GOx – FAD + H2O2
• 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.
H2O2 2H+ +O2 + 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.

12. Types of glucose biosensors
Enzymatic glucose biosensors
• First generation glucose biosensor
• Second generation glucose biosensor
• Third generation glucose biosensor
Non-enzymatic glucose
biosensors

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

14. 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.

15. 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.

16. 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.

17. 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.

18. 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/FADH2 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.

19. 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 OHads that mediate oxidation of the adsorbed species.

20. Glucose Biosensors Based on Carbon
Nanotube Nano electrode Ensembles
 The 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.

21. • 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.

22. 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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