Download Biosensors - Portal UniMAP

PTT 104: Introduction to Biotechnology
Department of Chemical Engineering Technology, UniMAP
Week 5: 10 October 2013
[email protected]
TECHNIQUES IN BIOTECHNOLOGY:
BIOSENSORS
COURSE OUTCOME
Able to demonstrate important recent advances in
methods and applications of biotechnology with
regards to microorganisms and plants.
Topic:
 Demonstrate the basic principles of Recombinant
DNA Technology and illustrate other methods used
in biotechnological field, to include tissue culture,
electrophoresis, Polymerase Chain Reaction (PCR)
and biosensor.

LECTURE OUTLINE

Biosensor Background
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What is a Biosensor?
Components of a Biosensor
Principles of Detection
Applications
INTRODUCTION TO BIOSENSORS

A biosensor is a special type of sensor
often used in bioanalysis.

Humankind has been performing
bioanalysis since the dawn of time,
using the sensory nerve cells of the
nose to detect scents and those of the
tongue to taste dissolved substances.
4
BIOSENSORS

Analogy with the nose as a sensor
(it is actually a biosensor).
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WHAT IS BIOSENSOR?
bioreceptor
Transducer
Biosensor
Bioreceptor: biomolecule that recognizes target analyte
Transducer: converts the recognition event into a measurable signal.
Biosensor: the two components are integrated into a single sensor.
Eg: glucose conc in blood sample can be measured directly by biosensor, by
simply dipping the sensor into the sample.
Advantages:
save time and cost
Require no specialized lab skills
1ST COMPONENT: BIOLOGICAL
ELEMENT/BIORECEPTOR
Component that is capable of recognizing a specific
target molecule.
Must be highly specific, stable under storage conditions, and immobilized.
Microorganism
Tissue
Cell
Organelle
Nucleic Acid
Enzyme
Enzyme Component
Receptor
Antibody
2ND COMPONENT: PHYSIOCHEMICAL
TRANSDUCER
Acts as an interface, measuring the physical change that occurs with the reaction at the
bioreceptor then transforming that energy into measurable electrical output.
Typically, this is done by measuring the change that occurs in the bioreceptor reaction.
Eg: enzyme glucose oxidase is used as a bioreceptor in a glucose biosensor that catalyzes
the following reaction:
Glucose + O2  Gluconic acid + H2O2
To measure glucose in a solutions, 3
different transducers can be used:
1. An O2 sensor that measures O2
conc
2. A pH sensor that measures acid
3. A peroxidase sensor that
measures H2O2 conc.
Transducer converts:
- O2 conc into electrical
current
- pH change into voltage
change
- H2O2 conc into electrical
current.
IMMOBILIZATION OF BIORECEPTOR
Major requirement for biosensor is the
bioreceptor be immobilized in the vicinity of the
transducer.
 Immobilization can be done via:
- Physical entrapment
- Chemical attachment
 Only minute quantity needed and used
repeatedly for measurements.
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PERFORMANCE CHARACTERISTICS OF
BIOSENSOR
Response time: time
required for the sensor
to indicate 63% of its
final response due to
change in analyte
conc.
-
Reproducibility:
accuracy of the output
obtained
Range: Conc range
over which the
sensitivity of the
sensor is good.
Detection limit: lowest
conc of the analyte to
which there is a
measurable response
Life time: period of the
sensor can be used
without significant
deterioration in
performance
Selectivity: ability of the
sensor to respond only
to target analyte.
Desired feature.
Sensitivity:
Response of sensor to
per unit change in
analyte conc.
Biosensor
characteristics
Stability: characterizes
the change in its
sensitivity over fixed
period of time
CONSIDERATIONS IN BIOSENSOR
DEVELOPMENT
Selection of a suitable
bioreceptor or recognition
molecule
Selection of suitable
immobilization method
Design of biosensor
considering measurement
range, linearity and
minimization of interference
and enhancement of
sensitivity
Selection and design of a
transducer that translate
binding reaction into
measurable signal
Packaging of the biosensor
into a complete device
TRANSDUCTION MECHANISMS IN BIOSENSORS
Conventional transducers
 Major transducers used:
- Amperometry: based on H2O2 and O2
measurement
- Potentiometry: based on pH or pI measurement
- Photometry: utilizing optical fiber
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AMPEROMETRY
Biorecognition reactions often generate
chemical species that can be measured using
electrochemical method.
 Eg: the reaction product is H2O2 can be
measured by a pair of electrodes.
 When suitable voltage is impressed on one of
the electrodes against a ref electrode (Ag/AgCl)
the target species (H2O2) is reduced and
generate electrical current.

POTENTIOMETRY
A glass or polymeric membrane electrode is
used for measuring membrane potential
 Resulting the difference in the conc of H+
across the membrane
 Measured for voltage

PHOTOMETRY
Light from indicator molecule is the measured
signal
 In this method, reactants/products of
biorecognition reaction results in colorimetric,
fluorescent or luminescent changes and
measured using photodetectors.

Examples
of biosensor:
Pregnancy test:
To detects the hCG
protein in urine.
Glucose monitoring device
(for diabetes patients):
To monitor the glucose level
in the blood.
Infectous disease
biosensor
Examples
Biosensor
for
research
works
of biosensor:
Ring
Sensor
Smart Shirt
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APPLICATIONS OF BIOSENSOR
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Health care/clinical diagnostics
Need a rapid and accurate methods of
detection.
Eg:diabetes (type I, type II and gestational):
detection of blood sugar levels
Insulin therapy: for treatment of insulindependent diabetes (Type I diabetes)
INDUSTRIAL PROCESS CONTROL
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Bioreactor control
The productivity depends on bioreactor conditions.
Real-time monitoring of carbon sources, dissolved
O2 and CO2 and products of metabolism in
fermentation can increased products yield at
decreased processing and material cost.
Using biosensors to improve the process
productivity.
MILITARY AND HOMELAND SECURITY
APPLICATIONS
Using sensors for chemical and biological
warfare agents.
 Rapid analysis: monitoring hazards due to
terrorist activity.
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ENVIRONMENTAL MONITORING
Environmental Protection Agency (EPA) Air and
Water Monitoring
 Environmental analytes:
 biological oxygen demand (BOD), atmospheric
acidity, and river water pH, detergent,
herbicides, & fertilizer concentrations in
drainage and river

MICROBIAL YEAST SENSORS
Biosensors using living immobilized microbes
play an important part in environmental testing
 Yeasts such as Trichosporon cutaneum and
Artxula adenivorans are the most frequently
used species to measure the organic pollution

The idea using microbial sensors developed
from the traditional measuring of the
Biochemical Oxygen Demand in 5 days
 By using Microbial Sensors, only 5 minutes are
required instead of 5 days.
 HOW????

The living yeast cells are immobilized in a
polymer gel and mounted on an oxygen
electrode.
 The sensor measures how much oxygen the
“starving” cells are taking up.
 When clean water, containing non degradable
substances, is added, the yeast does not take
up additional oxygen.
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