2. A biosensor is an analytical device which converts a biological
response into an electrical signal
It determine the presence and concentration of a specific
substance in a biological analyte
“A chemical sensing device in which a biologically derived recognition
is coupled to a transducer, to allow the quantitative development of
some complex biochemical parameter.”
Biosensor
DisplayBioreceptor Transducer Signal
Processing
Desired molecule
Introduction to Biosensors
Biosample
3.
4. Components of biosensor
Biosensors are composed mainly of two elements:
i. Bio-Receptors (biological material)
ii. Transducers (detector element)
iii. Associated electronics (signal conditioning circuit/amplifier, processor and a display unit.)
5. 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
6. Principle of a Biosensor
Immobilize biological material (specific enzyme) by conventional
methods
Biological material should be in close contact with the transducer
Analyte binds to the biological material to form a bound analyte
Bound analyte produces the measureable electronic response
Analyte can also be converted to a product
Product might be associated with the release of heat, gas (oxygen),
electrons or hydrogen ions
Transducer can convert the product linked changes into electrical signals
(ES)
Amplification and measurement of ES
8. i. Bioreceptors
Biological recognition elements that consist of
Immobilised biocomponent that can detect the specific target
analyte
ii. Transducer
Converts a biochemical signal into an electrical signal
Intensity of signal is directly or inversely proportional to the analyte
concentration.
On the basis of the transducing elements, biosensors can be classified into following types
i. Electrochemical (EC) (potentiometric, amperometric, etc)
ii. Optical type (fiber optics, etc)
iii. Mass based (piezoelectric, etc)
9. i. Electrochemical Sensors
allow analysis of biomolecules with high specificity,
sensitivity, and
selectivity,
Have low response time and are cost-effective
EC biosensors measure the current produced as a result of the oxidation
and reduction reactions.
In an EC reaction, a potential is applied to the WE and the resulting current is
measured versus time
Electrode is used as the transduction element
EC biosensors fall into one of four categories: amperometric, potentiometric,
impedance and conductometric
10. ii. Optical Sensors
Optical fibers allow detection of analytes on the basis of absorption,
fluorescence or light scattering
Catalytic and affinity reactions can be measured
The reaction causes a change in fluorescence or absorbance
Created due to change in the refractive index of the surface between two media
which differ in density
11. iii. Piezoelectric Sensors:
Piezoelectric sensor uses the piezoelectric effect to measure changes
in pressure, acceleration, temperature, strain, or force by converting them to an electrical
charge
piezoelectric effect: ability of a material to produce voltage when mechanically stressed
Antibodies and antigens appear as promising biomolecules well compatible with a piezoelectric
sensor
Polyclonal antibody against Francisella tularensis was prepared
Antibody was immobilized on surface of a 10 MHz quartz crystal microbalances (QCM)
In examined sample,
Interaction of antigen – antibody occurs and frequency changes up to 40 Hz.
13. Bioluminescence-based biosensors
Bioluminescence-based biosensors’s reporter genes:
Comprises the luxCDABE operon from the donor marine microorganism Vibrio
fischeri
The luxAB genes which encode luciferase from V. harveyi
Reporter phage
Luciferase gene has been infused into the genome of bacteriophage
Cell became bioluminescent phenotypically if that virus infects a host bacterium
Reporter phages are considered as a rapid tool for detection and identification of
microbial host cell
Detection limit:
Low as 10 E. coli and entero-bacterial cells
100 S. typhimurium cells
14. APPLICATIONS OF BIOSENSORS IN VARIOUS
FIELDS
Advantages of biosensors include
low cost,
small size,
quick and easy use,
sensitivity and selectivity
Clinical and Diagnostic Applications:
Electrochemical variety is used in clinical biochemistry
laboratories for measuring glucose and lactic acid.
key features of this is the ability for direct measurement on
undiluted blood samples.
15. Industrial Applications:
Monitoring of the delicate and expensive processes in industrial fermentation
Agricultural Industry:
Enzyme biosensors have been used:
to detect organophosphates and carbamates from pesticides
Microbial sensors for measurement of ammonia and methane.
Commercially available biosensors for wastewater quality control are
biological oxygen demand (BOD) analyzers
based on micro-organisms like the bacteria Rhodococcus erythropolis
immobilized in collagen or polyacrylamide.
16. FOOD INDUSTRY
Applications of enzyme based biosensors to food quality control include:
Measurement of amino acids, amines, amides, heterocyclic compounds,
carbohydrates, carboxylic acids, gases, cofactors, inorganic ions, alcohols,
and phenols
Used in industries for yogurt, and soft drinks
Immunosensors for detecting pathogenic organisms in fresh meat,
poultry, or fish.
Recombinant phage A511::luxABwas a feasible, sensitive detection of
viable Listeria cells in contaminated food
17. Presence of Escherichia coli in vegetables, (bioindicator
of faecal contamination)
Detecting variation in pH caused by ammonia (produced by
urease–E. coli antibody conjugate) using potentiometric
alternating biosensing systems
Wash the vegetables with peptone water provides to
have liquid phase
18. Quantum Dots (QDs) and QD-Based
Biosensors
A biosensor using QDs as an interface element
Quantum dots (QDs) are semiconductor nanocrystals with unique photophysical
properties and are comprised of elements from the periodic groups II–VI, III–V or IV–VI
A genetically-encoded FRET
biosensor developed for
detection of Bcr-Abl kinase
activity was used on cancer patient
19. Electrochemical biosensors used for glucose oxidase or glucose
dehydrogenase detection from blood to interstitial fluid
A noninvasive and non-contacting technique,
the wavelength modulated differential laser photothermal radiometry
(WM-DPTR), has been developed for continuous or intermittent glucose
monitoring
Can be applied to measure serum-glucose levels in human skin
21. Refrences
Anwarul Hasan et al., 2014. Recent Advances in Application of Biosensors
in Tissue Engineering.
Miroslav Pohanka. 2017. The Piezoelectric Biosensors: Principles and
Applications, a Review. Int. J. Electrochem. Sci. 12: 496-506.
Shagun Malhotra, Verma A., Tyagi N., Kumar V. 2017. Biosensors: principle
and applications. IJARIIE. 3: 3641-3644.
Sungyeap Hong and Cheolho Lee. 2018. The Current Status and Future
Outlook of Quantum Dot-Based Biosensors for Plant Virus Detection.
Plant Pathol. J. 34: 85-92.
Editor's Notes
They are based on the measurement of changes in resonance frequency of a piezoelectric crystal due to mass changes on the crystal structure.