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Biosensor

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  1. Biosensor M. Fatih Abasıyanık

  2. Biosensorsareactivelyused in science • Self-Monitoring of BloodGlucosewithGlucose Sensor has a market (8.8 BillionDollars in 2008) • Biosensor :

  3. Aim: • Understandtheparts of biosensors • Howtheywork • To be abletodiscriminatebiosensorsaccordingtotheirquality • To be abletodesignnewbiosensors • To be abletodiscussthepapersaboutbiosensors • To be abletoimprovebiosensors • To be abletoclassifyresults of sensors.

  4. Contents • Introduction to Sensors • Transduction Elements • Sensing Elements • Performance Factors • Electrochemical Sensors and Biosensors • Photometric Applications • Mass-Sensitive and Thermal Sensors • Specific Applications

  5. Book • “CHEMICAL SENSORS AND BIOSENSORS”

  6. Sensor? • A device or organ • To detects certain external stimuli and responds in a distinctive manner

  7. Basic sensors • An acid turns blue litmus paper red and a base turns red litmus paper blue

  8. pH meter

  9. Types • Physical sensors: measure • Distance • Mas • Temperature • Pressure • Chemical sensors: measure • Chemical substrances by chemical or physical response • Biosensors: measure • Chemical substrances by using a biological sensing element. • All of them  connected to a transducer visible response occurs

  10. Chemical Sensors and biosensors detect chemicals called analyte. • If analyte is a biomolecule, the device can be called biosensor Recognation element

  11. Types of transducer • Electrochemical biosensor: mostly used • Potentiometric: measure potential • Voltammetric : an increasing (decreasing) potential is applied to the cell until Ox. (re.) of the substrance to be analysed occure and a sharp rise (fall) in the current to give a peak. • Conductometric • FET based • Optical • Piezo electric • Thermal

  12. İmmobilization

  13. Performance factors • Selectivity • Sensitivity • Accuracy • Response time • Recovery time • Lifetime

  14. Biosensor: BiorecognationUnit (Sensing Element; biologicdetectionunit)

  15. SensingElements • Itis concerned with various ways in which a sensor can recognizean analyte. • specific for that analyte alone, • Selective ;responding to the required analytemore than to other species. Types of SensingElements • İonic (chemicalsensors) • Molecular (chemical sensor andbiosensor) • Biological (biosensor)

  16. A- IonicRecognation: Ion-SelectiveElectrodes • Possibleto be used in biosensors. • Example: urea ammonia • Theyare based on the principle of the emf of a concentration cell. • A potentiometric device in which the change in emf is proportional to the logarithmof the analyte concentration. • The selectivity by the membraneseparatingthe analyte solution from the internal reference solution. 0.0 0.5

  17. Interferences • Sensorsrespondto one ion more than to others, although there is often a small response tounwanted ions. This is known as interference. • For example, • a fluoride ISEresponds to hydroxide at one tenth of the response level (to fluoride) for equalconcentrations of the ions. • The level of interference is measured by the selectivitycoefficient • kij=the selectivity coefficient. 0.0 0.5 0.1 ISAB (ionic-strengthadjustmentbuffer): [OH] declinedto 10-9M pOH:9 . it is lowerthandetection limit for OH

  18. A- IonicRecognation: ConductingDevices • ionsconductorforelectreicty • quantitymeasurement • resistance (1/conductivity) • conductancedepends on…..; • degree of ionization (storngorweak) • charge of ion • number of ions • mobility of ions (relatedto size, smallfastermoreconductive) • conductivity not usedalone • ionchromography (extensivily)

  19. A- IonicRecognation: Modifiedelectrodes • selectivityimportant • electrodes not selectivealone • togain a selectivitymodifythem • twoways • modifythemselves • modifyitssurfacecoatedwithpolymers • modifythemselves • bestexampleCPE(Carbonpasteelectrode) suitableelectrodegraphitepowderwithNugola stiffpaste   mixwith a modifiedcomponent (electroactive;such as ferrocene) or a complexingagentextractingelectroactiveanalyteintothesurface of thepaste

  20. A- IonicRecognation: Modifiedelectrodes • modifyelectrodesurfacebycoatingwithdifferenttypes of polymers • Mainly 3 types • conductingpolymers • ion-exchangepolymers • redoxpolymers • a) Conductingpolymers • moststudiedones: polyacetylene, polypyrrole, polyanilineandpolythiophene • easytopolymerize: electrochemicallyoxidizingthesubstrade on theelectrode. • solventsandcounterions effect on thepolymer

  21. B- MolecularRecognition: 1. ChemicalRecognitionAgents  Thermodynamiclyrxnto be controlled M= analyte L=RecognitionAgent • M-L complex, or M or L respondto a particulartransducer (optical, electrochemicaletc) • Opticalresponse: an absorptionorfluorescencechangetotheanalyte • PVC (polyvintylchloride) successfullyusedforsuchbiosensor (ion-selectiveelectrodesalso) • Potentiometic e. (used)

  22. SomeApplicationwithsuchrecognitinagents • Analyte: Iron (II) • RecognationAgent: 2,2’-bipyridyl in a poly (vinylpyridine) (PVP) membrane. • Method: iron(II) oxidizedbylinear-sweepvoltametry. • Complexationrxn (M-L) accumulation of iron • İndicators can be usedtoanalyzetheanalytes. • Optodes: Opticalbiosensors (colorimeterorspectrophotometer)…. Usedtodetectthecolourchange

  23. Molecular Size: • Iftheanalyte is smallerthantheothers in thesample, size is selectiveandmolecularsievesareused as recognitionagent. Examples: • Theantibiotic, valinomycin is a neutralionophore • Makingcomplexwithpotassiumionsselectively • K fitsintoitscavity • Valionmycinused as a recognitionreagenttodetect K

  24. B- MolecularRecognition: 2. BiologicalRecognitionAgents • Biologicalsystemsthemajorselectiveelements • Theymustattachthemselvestooneparticularsubstrate, but not toothers. • Enzymes • Antibodies • Nucleicacids • Receptors Affinitybiosensors: Sensorswithantibodies of receptors as RecognitionElements

  25. 1. Enzymes • Free (purified) Enzmyes • TissueMaterials • Micro-organisms • Organelles (Mitochondria)

  26. Enzymes A. PurifiedEnzyme Manyenzymesoxidation-reduction (electrochemically) S:substrate ; E: Enzyme; ES:enzyme-substratecomplex; P:product

  27. enzymes Michaelis-MentenEquation

  28. enzymes

  29. enzymes Double-reciprocal plot

  30. AdvantagesandDisadvantages of usingEnzymes in sensors ADVANTAGES DISADVANTAGES • Highlyselective • Catalyticallyactiveimprovesensitivity • Fairlyfast-acting • One of themostknownbiologicalcomponents • Expensive • A lossactivitywhenimmobilized on a transducer • Tendingtoloseactivityafter a relativelyshortperiod time

  31. enzymes B. TissueMaterials: • Tissuemultiplicity of enzymes • Thus, not selective as purifiedenzymes • But, longer life protected (in itsenviron.) • Responseslow (diffusion) • Cheaper • Example: Banana tissue sensor: • [Eggins (1997)] Banana biosensor

  32. enzymes • Fordopamine, a catcholaminefound in braincontaining a complex of polyphenolaseswhichcatalysetheoxidation of polyphenoliccompounds • İtsderivatives: flavanolsfound in beersandwine • Polyphenoloxidasecatalysetherxn. • İt is found in banana

  33. enzymes • Advantages: • Enzyme in naturalenvironment • Activitystable • Lessexpensive • Theysometimesworkwhenpurifiedenzymes fail • Disadvantages: • Lossselectivity • Diffusionproblems

  34. enzymes C. Microorganisms: • Theyplayimportant role in • Brewing • Pharmaceuticalsynthesis • Foodmanufacture • Waste-watertreatment • Energyproduction • MO immobilizedtotransducerdirectly • MO can ….. • Assimilateorganiccompounds • Produceelectroactivemetabolites

  35. enzymes • Advantages: • Cheaper • Lesssensitivetoinhibitonbysolutes, moretoleranttopH & temperature • Longerlifetimes • Disadvantages: • Longerresponse time • Longerrecoveryactivitytimes • Manyenzymesandlessselectivity

  36. enzymes D. Mitochondria (organelles) • Sub-cellularmulti-enzymeparticelscatalyze an analyte

  37. antibodies 2. Antibodies: • Versitile (largespectrum) • Possibletodevelopeforanyantigen • İtsfunction: tobind an invadingantigenandremove it fromharm

  38. Heavy chain hinges Fab: antigen-binding fragment light chain Fc: crystalizable F Gerald edelman & Rondey porter

  39. antibodies • Labelling Ab • Radioisotopes • Enzymes • Redcells (RBC) • Fluorescentprobes • Chemiluminescentprobes • Metal tags • Masschangeetcalso can be seen

  40. antibodies • Advantages: • Highselectivity • Ultra sensitive • Bindverypowerfull • TNT also can be detectedbyantibodies R.D. Shankaran, K.V. Gobi, K. Matsumoto, T. Imato, K. Tokoand N. Miura, Highlysensitivesurfaceplasmonresonanceimmunosensorforparts-per-trillionleveldetection of 2,4,6-trinitrophenol, Sens. Actuators B: Chem.100 (2004), pp. 425–430. • Disadvantages. • No catalytical

  41. nucleic acids 3. Nucleic Acids: • likeantibodies • DNA probesusedtodetectgeneticdiseases, cancersandviralinfections • DNA assays can involvetheaddition of labelled DNAtothesystem • Radioactive • Photometric • Enzymic • Electroactive

  42. nucleic acids • Examplesto NA biosensor

  43. 4. Receptors: • A receptor is a structure in a cell, which can trigger an amplified physiological response when it is bound to a particular ligand (an agonist). • An agonist a chemical binding to a receptor and triggers a response by the cell. An agonist often mimics the action of a naturally occurring substance.An agonist produces an action. An antagonist blocks an action of an agonist. The response may be either … • ion-channel opening, • production of second messenger systems, or • activation of enzymes.

  44. Receporstendtohave an affinityfor a range of structuralrelatedcompounds. • Likeothers, alsotheyarelabelled • Examples: • BiosensorforAnaestherics

  45. Transducers

  46. Types of transducers • ElectrochemicalTransducers • Potentiometric • VoltammetryandAmperometric • Conductivity • FieldEffectiveTransistors • PhotometricSensors • Others

  47. ElectrochemicalTransducers

  48. metal (such as silver) is placed in a solution containing ions (such as silver ions), there is a charge separation across the boundary betweenthe metal and the solution. an electronpressure, usuallytermed a porential. It cannot be measured directly, and requires two such electrode-electrolyte combinations. Each of these is called a half-cell.Such a combination is called an electrochemical cell