i. A biosensor consists of a bioreceptor element and a transducer. The bioreceptor detects the analyte and the transducer converts the biological response into an electrical signal. ii. Biosensors have various applications in clinical diagnosis, food safety, environmental monitoring and more. Electrochemical biosensors are commonly used in clinical settings to detect glucose and lactate levels. Optical and piezoelectric biosensors also have applications in detecting pathogens, chemicals and other biomolecules. iii. Emerging technologies like quantum dots are expanding biosensor applications. For example, quantum dot biosensors show potential in noninvasive glucose monitoring and cancer detection. Overall, biosensors provide sensitive, rapid and cost-effective

1. Biosensors
MICBIO: biosensors and its applications.

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

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

7. Measurement flow for a biosensor

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.

12. Assays by piezoelectric biosensors

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

20. Question

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.