2. INTRODUCTION
• A biosensor is a self-contained integrated device that is capable of
providing specific quantitative or semi-quantitative analytical
information using a biological recognition element which is
in direct spatial contact with a transduction element. A
biosensor isananalyticaldevice containinganimmobilized biological
material (enzyme,antibody,nucleic acid,hormone,organelleorwhole
cell)whichcanspecificallyinteract withananalyte andproducephysical,
chemicalorelectricalsignalsthatcan bemeasured.An analyteisa
compound(e.g.glucose,urea,drug, pesticide)whoseconcentrationhasto
bemeasured.
3. BASICPRINCIPLE OF BIOSENSOR
The desired biological material is immobilized by
conventional methods (covalent or non-covalent
binding).This immobilized biological material is in
intimate contact with the transducer. The analyte
binds to the biological element to form a bound
analyte which in turn produces the electronic
response that can be measured.
• WORKING PRINCIPLE
1. Analyte diffuses from the solution to the surface of the
Biosensor.
2. Analyte reacts specifically and efficiently with the biological
component of the Biosensor.
3. This reaction changes the physiochemical properties of the
transducer surface.
4. This leads to a change in the optical/electronic properties
of the transducer surface.
5. The change in the optical/electronic properties is
measured and converted into electric signal, which is
detected.
4. TYPESOFBIOSENSORS
Based on bio receptors:
• Enzyme biosensor
• Microbial biosensor
• Affinity biosensor
Based on transducer:
• Potentiometric biosensor
• Amperometric biosensor
• Conductometric biosensor
• Optical biosensor
• Acoustic or piezoelectric
1)Itshouldbehighlyspecificfortheanalyte.
2)Thereactionusedshouldbeindependentofmanageablefactors likepH,temperature,stirring,etc.
3)Theresponseshouldbelinearoverausefulrangeofanalyte concentrations.
4)Thedeviceshouldbetinyandbio-compatible.
5)Thedeviceshouldbecheap,small,easytouseandcapableof repeateduse.
FEATURES OF BIOSENSOR
5. ELECTROCHEMICALBIOSENSOR
• Electrochemical biosensors are normally based on enzymatic catalysisof a reaction that produces or
consumes electrons (such enzymes are rightly called redox enzymes). The sensor substrate usuallycontains
three electrodes: a reference electrode, a workingelectrode and a counter electrode. The target analyte is
involved in the reaction that takes place on the activeelectrode surface, and the reaction maycause either
electron transfer across the double layer(producing a current) or can contribute to the double layerpotential
(producing a voltage). Wecan either measure the current (rate of flow of electrons is now proportional to the
analyte concentration) at a fixed potential or the potential can be measured at zero current (this givesa
logarithmic response)..
6. AMPEROMETRICBIOSENSORS
• Amperometric biosensors are self- contained integrated devices based on the
measurement of the current resulting from the oxidation or reduction of an electro-
active biological element providing specific quantitative analytical information.
• Amperometricbiosensorsfunctionbytheproductionofa currentwhenapotentialisapplied
betweentwoelectrodes. Themagnitudeofcurrentbeingproportionaltothesubstrate
concentration.Thesebiosensorsareused tomeasureredoxreactions.
7. PIEZOELECTRIC SENSORS
• Piezoelectric sensors utilizecrystalswhichundergo an elasticdeformation when an electricalpotential is
applied to them. An alternating potential (A.C.) produces astanding wavein the crystalat acharacteristic
frequency.This frequency ishighlydependent on the elasticproperties of the crystal,such that ifacrystalis
coated with abiologicalrecognition element the binding of a (large)target analyteto areceptor will
produce achange in the resonance frequency,whichgivesabinding signal.In amode that uses surface
acoustic waves(SAW),the sensitivityisgreatlyincreased. This isaspecialized applicationof the Quartz
crystalmicrobalance asa biosensor.
Acousticsensorsusepiezoelectricmaterials,typicallyquartzcrystals,inordertogenerateacousticwaves.Theirsurfaceis
usuallycoatedwithantibodieswhichbindto thecomplementaryantigenpresentinthesamplesolution.Thisleadsto
increasedmasswhichreducestheirvibrational frequency;thischangeisusedtodeterminetheamountofantigen present
inthesamplesolution.
8. OPTICALBIOSENSOR
• Optical biosensors have high specificity,sensitivity,smallsize and cost-effectiveness. Multipleadvanced concepts and
highly multidisciplinary approaches including microelectronics, microelectromechanical systems (MEMSs),
micro/nano- technologies, molecular biology,biotechnology and chemistry are applied in the implementation of
new optical biosensors.
• They measure change in light absorption asreactants are converted into products.
• Photon output for luminous or fluorescent process can be
• detected with photomultiplier tubes or photodiode systems.
Theseinvolvedeterminingchangesinlightabsorptionbetween thereactantsandproductsofareaction,ormeasuringthelight output
byaluminescentprocess.A mostpromisingbiosensorinvolvingluminescenceuses fireflyenzymeluciferasefordetectionofbacteriain
foodorclinicalsamples.
9. APPLICATIONSOF BIOSENSORS
Food Analysis
Study of biomolecules and their interaction
Drug development
Crime detection
Medical diagnosis(both clinical and laboratory
use)
Environmental field monitoring
Quality control
Industrial Process Control
Detection systems for biological warfare agents
Manufacturing of pharmaceuticals and
replacement organs.
• Biological Applications:
• DNA sensors : genetic monitoring,
• disease diagnosis .
• Immunosensors: HIV, hepatitis.
• Cell based sensors: functional sensors ,
drug testing.
• Point-of-care sensors: Urine ,
• blood, steroids.
10. THE ROLE OF BIOSENSORS IN COVID-19
EC biosensors
• EC biosensors have attained much attention of the analytical researchers because of their simplicity, low cost, ease in miniaturization
and bulk fabrication. They have also point-of-care usability at homes or at clinics. Due to the absence of any vaccine or specific drugs
available for the treatment of COVID-19 infection, early diagnostics are the only way to manage and combat with this virus. The MERS-
CoV and other human CoV have been detected by Eissa's research group using recombinant spike protein S1 which acted as a
biomarker for MERS-CoV and the design of multiplexed electrode array has been presented in Figure A. The bioassay with turnout of
20 min achieved low detection limits of 0.4 pg/mL and 1 pg/mL for human CoV and MERS-CoV, respectively . The fabricated EC
immunosensor was fruitfully employed in spiked nasal samples and no any obvious interference was measured in the presence of
influenza A and B. Another simple, economical, and easy-to-use EC genosensor was constructed on gold films by Abad-Valle et al. for
the detection of SARS-CoV gene. The genosensor achieved a detection limit of 6 pM for this DNA sequence applying square wave
voltammetry.
11. CANCERDETECTION
• Weknow canceristhe first leadingcauseof death in the world.There are nearly200distinct forms mainlylung, prostrate, breast, ovarian,skin etc.
• The use of biosensors in cancer detection and monitoring holds vastpotential. Biosensors can be designedto detect emergingcancerbiomarkers and to determine
drug effectiveness at varioustarget sites.Biosensor technology has the potential to provide fast and accuratedetection, reliableimagingof cancercells,and
monitoring of angiogenesisand cancermetastasis,and the abilityto determine the effectiveness of anticancer chemotherapy agents.
• Biomarkerscan be of variousmolecular origins, includingDNA(ie., specificmutation, translocation, amplification, and loss of heterozygosity),RNA, or protein(ie.,
hormone, antibody, oncogene, or tumor suppressor).
• In terms of cancer, the analytebeingdetected bythe biosensor isatumor biomarker. Thus, bymeasuring levelsof certain proteins expressed and/or secreted by
tumor cells,biosensors can detect whether atumor ispresent, whether it isbenign or cancerous, and whether treatment has been effective in reducing or eliminating
cancerous cells.Biosensors that can detect multipleanalytesmayprove particularlyuseful in cancer diagnosisand monitoring, sincemost typesof cancer involve
multiple biomarkers. The abilityof abiosensor to test for multiplemarkers at once not only helps with diagnosis, but alsosaves time and financial resources.
• Piezoelectric and acousticwavebiosensors make up the classof mass-based biosensors. In terms of cancer detection, piezoelectricbiosensors are more commonly
used. Piezoelectric sensors are based on changes in the mass of quartz crystals when potential energy isapplied to them. This change in mass generates afrequency,
whichcan be converted into asignal. Immunosensors and microcantileversensors that use piezoelectrictechnology have proven useful in the identification of cancer
biomarkers.The unique feature of these sensors isthat theyidentifychange in mass in nanoscale,and hence used for early detection whichismandatory in certain
forms of cancer ;especiallybreast cancer.These sensors are user friendlyand it provides privacyfor patients to detect certain cancers like
breast,ovarian,prostrate,cervical etc.at early stages.
12. PREGNANCYTEST
• hCG(human chorionic gonadotropin) is a hormone secreted in pregnancy that is made by the developing
embryo soon after conception.
• This hormone is detected using a biosensor strip.The widely used strip uses manual reading technique
which employs lateral/ capillary flow assay.The other method uses digital biosensor technology which
givesa positive result only in the presence of hCG hormone in urine.The advantage of this is that the
chance of getting a wrong result is less;as it’smore specific.The reason for its less acceptance in the society
is due to higher cost compared to the former one.
13. EPIGENETICS
photonicbiosensorshavebeendeveloped,whichcan
detect tumorcellinaurinesampletoanultra-
sensitivitylevel.
epigeneticmodificationsaredetectedafterexploitation
of integratedopticalresonators(e.g.,post-translational
modificationsin histoneanddna methylation)using
bodyfluidsofpatientssuffering fromcancerorother
ailments.
BiosensorsinDrugDiscoveryandDrug Analysis
Enzyme‐basedbiosensorscanbeappliedin
thepharmaceutical industryformonitoring
chemicalparametersintheproduction
process(inbioreactors).
Affinitybiosensorsare suitablefor
high‐throughputscreeningof
bioprocess‐producedantibodies and for
drugscreening.
Oligonucleotide‐immobilizedbiosensorsfor
interactionsstudies betweenasurfacelinked
DNAandthe target drug or for
hybridisation studies.
Biosensorsin Food Industry
• Biosensors areusedforthedetectionofpathogens in food.
• PresenceofEscherichia coli invegetables,isabioindicator offaecal
contaminationin food.E. coli has been measured by detecting variationin
pHcausedbyammonia(producedbyurease–E.
• coli antibodyconjugate)using potentiometricalternatingbiosensing
systems.
• Enzymaticbiosensors arealsoemployedinthedairyindustry
.
