Biosensor

Miss. VRUSHALI V. DHOBLE
(sneha.dhoble@gmail.com)
Assistant Professor, Department of
Biotechnology
Walchand College of Arts and Science, Solapur
www.wcassolapur.org

Learning Outcomes
 At the end of this session students will be able to explain basic principle of
biosensor.
 Students will be able to describe function and application of glucose
oxidase biosensor, cholesterol biosensor, urease biosensor and antibodies as
biosensor.
2Walchand Centre For Biotechnology, WCAS,Solapur

Introduction
• A biosensor is an analytical device which is used for the detection of an
analyte.
• Biosensor consist of immobilized biological material ( enzyme, antibody,
nucleic acid, hormone, organelle etc) which can specifically interact with an
analyte and produce physical, chemical or electrical signals that can be
measured.
• An analyte is a compound whose concentration has to be measured.
Biosensor Device

 The interaction between the ana-lyte and the receptor on the solid biosensor
surface is detected either by a change in the refractive index or by changes
in the fluo-rometric intensity, ultraviolet light intensity, etc.
 Leland C Clark is the father of biosensor.
 He invented glucose biosensor to determine
glucose level in diabetic patient.
Glucose biosensor

Diagrammatic representation of biosensor

Basic Principle Of Biosensor
 The biological material is immobilized and a contact is made between the
immobilized biological material and the transducer.
 The analyte binds to the biological material to from bound analyte which in turn
produces the electronic response that can be measured.
 Sometimes the analyte is converted to a product which could be associated with the
release of heat, gas (oxygen),electrons or hydrogen ions.
 The transducer then converts the product linked changes into electrical signals
which can be amplified and measured.

First Component-Biological element
 The component used to bind the target molecule. Must be highly specific,
stable under storage conditions and immobilized.
 Example :- Microorganism, tissue, cells, nucleic acid, enzyme, antibody.
Function-
 To interact specifically with target compound i.e the compound to be
detected.
 It must be capable of detecting the presence of target compound in test
solution.

Second Component- Transducer
 Acts as interface, measuring the physical change that occurs with the
reaction at the bioreceptor then transferring that energy into measurable
electrical output.
Types of Transducer

Third Component Detector
 Signals from transducer are transferred to
processor where they are amplified and analyzed.
 The date is then converted into measurable
units then transferred to display or storage device.
Detector

Application
 Biosensors are used for the detection of glucose in the management of
diabetes mellitus (DM).
 Biosensors are used for the detection of pathogens in food.
 Biosensors can be used for military purposes at times of biological attacks.
 Used for the detection of pesticides and river water contaminants such as
heavy metal ions.

Glucose Biosensor
 Enzyme glucose oxidase catalyzes oxidation of glucose by molecular
oxygen producing glucolactone and H2O2.
 Glucose oxidase requires a cofactor FAD ( flavin adenine dinucleotide) as
an electron acceptor for its activity is reduced to FADH2
Reaction by glucose oxidase enzyme

 The cofactor is regenerated by reacting with oxygen, leading to the
formation of hydrogen peroxides.
 Hydrogen peroxide is oxidized at a catalytic, classically platinum (Pt)
anode. The electrode easily recognizes the number of electron transfers, and
this electron flow is proportional to the number of glucose molecules
present in blood.

Three general strategies are used for the electrochemical sensing of glucose;
 By measuring oxygen consumption
 By measuring the amount of hydrogen peroxide produced
 By using diffusible or immobilized mediator to transfer electron from
enzyme to electrode

Cholesterol Oxidase Biosensor-
 Estimation of cholesterol level in blood is most important and challenging
task in medical field.
 Conventionally lieberman- Buchard test were used to determine
cholesterol level in blood.
 Lieberman- Buchard is a reagent used in colorimetric test to detect
cholesterol, which gives a deep green colour.
 This test uses acetic anhydride and sulfuric acid as reagent.

 ChOx catalyzes the oxidation of the C3‐OH group of cholesterol
(and other sterols) to give the corresponding Δ5‐3‐ketone
(cholest‐5‐en‐3‐one).
 A cholesterol biosensor is prepared by immobilizing cholesterol
oxidase enzyme in a layer of silica gel matrix on carbon electrode.
 It is based on detection of hydergen peroxide produced by oxidase
enzyme.

Urease Biosensor
 Urease catalyzes the hydrolysis of urea to ammonia and carbon
dioxide.
 A urease biosensor for the determination of urea in solutions and
blood serum is made by immobilising urease in a bovine serum
albumin membrane.

Antibodies As Biosensor
 Immunosensors worked on the principle of immunological specificity
coupled with measurement based on amphometric and potentiometric
biosensor.
 There are several configuration for immuno sensors some of them are-
 An immobilized antibody to which antigen can bind directly.
 An immobilized antigen that can bind to antibody which in turn can bind
to free second antigen.
 An immobilized antibody binding free antigen an enzyme labelled
antigen in compitition.

Reference
 Biosensors fundamentals and applications, 2nd edition by Chandra Mouli
Pandey, Bansi Dhar Malhotra.
 Introduction to biosensors from electric sensors to immunosensors, 2nd
edition by Jeong- Yeol Yoon.
Walchand Centre For Biotechnology, WCAS,Solapur 19

Thank You..

Biosensor

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