ABSTRACT

Abiosensormaybebroadlydefinedasanymeasuringdevicethatcontainsabiologicalelement.Aschematicdrawingforagenemlizedbiosensor isshowninFigure1.1.Atargetanalyte(illustratedbysolidcircles)inthe externalmediummustbeabletoenterthebiosensor.Theexternalmembraneofthebiosensormustbepermeabletotheanalyte,andifpossible, excludeotherchemicalspeciesthatthebiosensormightalsobesensitiveto. Thebiologicalelementinsidethebiosensortheninteractswiththeanalyte andrespondsinsomemannerthatcanbedetectedbyatransducer.Thebiologicalelementmayconverttheanalytetoanotherchemicalspecies(representedbyopencircles)throughabiochemicalreaction;produceorrelease anotherchemicalproductinresponsetotheanalytestimulus;changeits optical,electricalormechanicalproperties;ormakesomeotherresponse thatcanbereliablyquantified.Theremaybeanotherinternalmembrane nearthetransducerwhichmighthavedifferentpermeabilitypropertiesthan theexternalmembrane.Theoutputsignalfromabiosensordependsonthe typeoftransducerituses.Thetransducermaybeaconventionalelectrochemicalsensor,ormaybebasedonanothertechnology.