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Low-cost, portable biosensors for Escherichia coli detection in water

Maas, Michael Benjamin (2015-12)

Thesis (MEng)--Stellenbosch University, 2015.


ENGLISH ABSTRACT: Low-cost, portable biosensors for the detection of Escherichia coli (E. coli) in water were investigated. The operating principle of various biosensors is discussed at the hand of a biosensor model. These methods, including electrical and optical methods, are evaluated for use in low-cost sensors. An electrically and optically based biosensor are compared. An electrochemical impedance biosensor that detects bacteria using non-linear AC harmonics is evaluated. Various electrode geometries and materials patterned on glass chips were tested. Ionic solutions were tested and a sensitivity of 0.01 mg/L for NaCl, KCl and MgCl2 was achieved. E. coli B44 was tested, and bacterial concentration curves for the sensor was derived. The limit of detection (LOD) of the sensor was 1.1 x 1010 CFU/ml, and the response time less than 4 minutes. A fiber-optic biosensor, operating using evanescent wave modulation, was tested. A low-cost testing method, using simple optoelectronics, was derived and hand-made fibers were manufactured. The fibers were immobilised with primary anti-E. coli antibodies by covalent attachment with a (3-Glycidyl oxypropyl) trimethoxysilane (GPS) crosslinking agent. The immobilisation efficiency was determined using Wide Field Fluorescence microscopy. Bacterial concentrations (E. coli DH5 ) were tested, and bacteria was successfully detected. The LOD of the sensor was 3 x 107 CFU/ml, and the response time less than 120 minutes. The two sensors are compared and evaluated for use in low-cost, portable biosensing systems for water testing. Recommendations for future development of a low-cost, portable biosensing prototype is discussed, including a system model and possible specifications. Possible applications for future biosensor development is discussed in detail.

AFRIKAANSE OPSOMMING: Lae-koste, draagbare biosensors vir die opsporing van Escherichia coli (E. coli) in water word ondersoek. Die opsporingsmetode van onderskeie biosensors word bespreek, met die hulp van 'n biosensor model. Hierdie metodes, insluitend elektroniese en optiese metodes, word evalueer vir gebruik in lae-koste sensors. 'n Elektroniese en opties gebaseerde biosensor word vergelyk. 'n Elektrochemiese impedansie biosensor wat bakterieë opspoor met behulp van nie-lineêre WS harmoniese pieke word evalueer. Verskeie elektrode geometrie ë en materiale, wat op glass skyfies geëts is, is getoets. Ioniese oplossings is getoets en 'n sensitiwiteit van 0.01 mg/L vir NaCl, KCl en MgCl2 is bepaal. E. coli B44 is ook getoets, en bakteriële konsentrasiekurwes is afgelei. Die limiet van opsporing van die sensor was 1.1 x 1010 KVE/ml, en die reaksietyd minder as 4 minute. 'n Optiese vesel biosensor, wat van verganklike golfmodulasie gebruik maak, is getoets. 'n Lae-koste toetsmetode, wat gebruik maak van eenvoudige optoëlektroniese komponente, is ontwerp en handgemaakte vesels is vervaardig. Die vesels is geïmmobiliseer met primêre teenliggaampies deur kovalente bindings met 'n (3-Glycidyloxypropyl) trimethoxysilaan (GPS) kruisbindingsagent. Die immobiliseringseffektiwiteit is bepaal deurWye Veld Fluoressensie mikroskopie. Bakteriële konsenstrasies (E. coli DH5 ) is getoets, en bakterieë is opgespoor. Die limiet van opsporing van die sensor was 3 x 107 KVE/ml, en die reaksietyd minder as 120 minute. Die twee sensors is vergelyk en evalueer vir gebruik in lae-koste, draagbare biosensorstelsels vir watertoetse. Voorstelle vir die toekomstige ontwikkeling van 'n eenvoudige, draagbare biosensor-prototipe word bespreek, insluitend 'n stelselmodel en moontlike spesifikasies. Moontlike toepassings vir toekomstige biosensor ontwikkeling word in detail bespreek.

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