Biosensors

BIOSENSORS

By
Dr.Arun Babu.N.B.
I Yr M.D. Biochemistry
V.M.K.V.M.C.,Salem.

DEFINITION
 Self-contained integrated device that is capable of
providing specific qualitative or semi-quantitative
analytical information using a biological
recognition element which is in direct-spatial
contact with a transduction element.
(IUPAC,1998)

CURRENT DEFINITION
A sensor that integrates a biological element with a
physiochemical transducer to produce an
electronic signal proportional to a single analyte
which is then conveyed to a detector.

 Any device that has specific biochemical
reactions to detect chemical compounds in
biological samples.

FATHER OF BIOSENSOR.
Professor Leland C Clark Jnr
(1918–2005)

COMPONENTS

Detector

BIOSENSOR.

Analyte
Response

Analysis Detection Sample
handling/preparation
Signal

THE ANALYTE.
(What do you want to detect?)
Molecule
Protein, toxin, peptide, vitamin, sugar, metal ion

Cholera toxin Glucose

SAMPLE HANDLING.
(How to deliver the Analyte to the Sensitive Region?)

•(Micro) fluidics
•Concentration (increase/decrease)
•Filtration/selection

DETECTION/RECOGNITION.
(How do you specifically recognise the analyte?)
Fab

Active site Membrane receptors
Competitive binding

Fc
Antibody Enzyme Cell Polymer/Hydrogel

SIGNAL
(How do you know there was a detection?)
Specific recognition?
Common Signalling Principles
Optical(SPR,ELM,IR).
Electrical(Voltametry,Potentiometry,
Conductivity).
Electromechanical(QCM).
Thermal.
Magnetic.
Pressure.

Often the detector is immobilized on a solid support/sensor.
(The immobilisation permits repeated use of the costly Biological
Molecule.)

WORKING PRINCIPLE
Analyte diffuses from the solution to the surface of
the Biosensor.
Analyte reacts specifically & efficiently with the
Biological Component of the Biosensor.
This reaction changes the physicochmical properties
of the Transducer surface.
This leads to a change in the optical/electronic
properties of the Transducer Surface.
The change in the optical/electronic properties is
measured/converted into electrical signal, which is
detected.

BASIC CHARACTERESTICS

 LINEARITY - Should be High – For the
detection of High Substrate Concentration.
 SENSITIVITY - Value of Electrode Response
per Substrate Concentration.
 SELECTIVITY - Chemical Interference must be
minimised for obtaining Correct Result.
 RESPONSE TIME – Time necessary for having
95% of the Response.

ADVANTAGES

Highly Specific.
Independent of Factors like stirring, pH, etc.
Linear response, Tiny & Biocompatible.
Easy to Use, Durable.
Require only Small Sample Volume.
Rapid, Accurate, Stable & Sterilizable.

TYPICAL SENSING TECHNIQUES
 Fluorescence.
 DNA Microarray.
 SPR (Surface Plasma Resistance).
 Impedance Spectroscopy.
 SPM (Scanning Probe Microscopy, AFM, STM).
 QCM (Quartz Crystal Microbalance).
 SERS (Surface Enhanced Raman Spectroscopy).
 Electrochemical.

TYPES
 Calorimetric/Thermal Detection Biosensors.
 Optical Biosensors.
 Resonant Biosensors.
 Piezoelectric Biosensors.
 Ion Sensitive Biosensors.
 Electrochemical Biosensors.
 Conductimetric Sensors.
 Amperometric Sensors.
 Potentiometric Sensors.

 Calorimetric / Thermal Detection Biosensors.
 Uses Absorption / Production of Heat.
 Total heat produced/absorbed is ᾶ Molar
Enthalpy/Total No. of molecules in the rn.
 Temp. measured by Enzyme Thermistors.
Advantages:
• No need of Frequent recalibration.
• Insensitive to the Optical & Electrochemical
Properties of the sample.
Uses:
Detection of: (1) Pesticides .
(2) Pathogenic Bacteria.

 Optical Biosensors.
 Colorimetric for colour - Measures change in
Light Adsorption.
 Photometric for Light Intensity - Detects the
Photon output.

 Resonant Biosensors.
 An Acoustic Wave Transducer is coupled with
Bioelement.
 Measures the change in Resonant Frequency.

 Piezoelectric Biosensors.
 Uses Gold - To detect specific angle at which ȇ waves
are emitted when the substance is exposed to laser
light/crystals like quartz, which vibrates under the
influence of an electric field.
 Change in Frequency ᾶ Mass of Absorbed
material.
 Ion Sensitive Biosensors.
 Are semiconductor FETs with ion-sensitive surface.
 Surface Electrical Potential changes when the ions &
semiconductors interact.
 Measures the Change in Potential.
Uses:
o pH Detection.

 Electrochemical Biosensors.
Underlying Principle – Many chem.rns produce or
consume ions or ȇs causing some change in the
elctrical properties of the solution that can be sensed
out & used as a measuring parameter.
Uses:
Detection of :
o Hybridized DNA
o DNA- binding Drugs &
o Glucose Concentration.
 Conductimetric Sensors.
 Measures Electrical Conductance/Resistance of the
solution.

 Conductance Measurements have relatively Low
Sensitivity.
 Electrical Field is generated using sinusoidal(ac)
voltage, which helps in minimizing undesirable
effects like:
i. Faradaic processes.
ii. Double layer charging &
iii. Concentration polarization.

 Amperometric Biosensors.
 High Sensitivity Biosensor.
 Detects electroactive species present in the
biological test samples.
 Measured Parameter – Current.

 Potentiometric Sensors.
 Working Principle – When ramp voltage is
applied to an electrode in solution, a current flow
occurs because of electrochemical reactions.
 Measured Parameter – Oxidation / reduction
Potential of an Electrochemical rn.

Food Analysis.
Study of Biomolecules & their Interaction.
Drug Development.
Crime Detection.
Medical Diagnosis (Clin&Lab).
Environmental Field Monitoring.
Quality Control.
Industrial Process Control.
Detection Systems for Biological Warfare Agents.
Manf. Of Pharmaceuticals & Replacement organs.

BIOSENSOR FOR AGRICULTURAL
& FOOD INDUSTRY.
o Detection of viral, fungal, bacterial diseases of
plants.
o In food industry, detection of total microbes &
food quantification in soft drinks.
o To determine the freshness of other fish, beef &
other food items.
o Makes Bacteria GLOW by OPTICAL Biosensor

The DNA capture Glucometer- for
element instrument- for measurement of
hereditary diseases glucose in blood.

Pregnancy Test. Infectious Disease Biosensor.
•Detects the hCG protein in urine. •Data analysis and interpretation
• Interpretation and data analysis performed by a microprocessor.
performed by the user.

Old time coal miners’ Biacore Biosensor platform.
Biosensor. General and flexible, good tool for
Data analysis and interpretation development of specific biosensors.
performed by the coal miner.

BIOSENSOR FOR DETECTION OF POLLUTION &
OF THE CHEMICALS PRESENT IN THE
ENVIRONMENT.

Biosensors

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