Design of an electrochemically reactive HIV DNA biosensor by use of hairpin DNA Probes on carbon nanofibers.

Lawrenson, Nicholas (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: A low cost, electrochemical HIV DNA biosensor was investigated using hairpin DNA probes immobilized on carbon nanofibers. The basic biosensor model, as well as electrochemical and optical based biosensor techniques, were explored. The electrochemical and optical techniques were evaluated for use in low-cost HIV DNA detection. A resistive based electrochemical technique was chosen to detect the presence of HIV single stranded DNA. A carbon nanofiber mat was used as the selected transducer, with hairpin probe DNA immobilized by self assembled monolayers. The self assembled monolayers were formed by gold-thiol bonding where gold was sputter coated onto the carbon nanofibers. The immobilization of the hairpin probe was validated by use of a fluorescent label and confocal microscopy. A high precision and low current sensing circuit was designed to detect the change in resistance of the transducer during a hybridization event. A user friendly graphic user interface was designed to conduct, display and record all data during testing. A ferrocene labelled hairpin probe was used for all electronic based testing. It is believed that a ferrocene modification will increase electrochemical reactions in biosensors. It was found that the designed hairpins operated as expected during fluorescent based testing, but it was not possible to obtain an electronic signal. Various post processing methods were explored to increase the chance of detection of HIV DNA and it was found that the sensor was able to detect the addition of a sample solution, but not necessarily HIV DNA. Various optimizations and alternative solutions were suggested and it is believed that, with some minor changes, a resistive based biosensor to detect HIV DNA is very possible.

AFRIKAANSE OPSOMMING: 'n Lae-koste elektrochemiese MIV DNS biosensor is ondersoek deur middel van haarnaald DNS probes wat aan koolstof nanovesels vasgeheg was. Basiese biosensor modelle, insluitende elektrochemiese en optiese tegnieke, was ondersoek. Die elektrochemiese en optiese tegnieke is geevalueer vir lae-koste MIV DNS herkenning. Dit was gekies om gebruik te maak van 'n elektriese weerstand-gebaseerde elektrochemiese meet tegniek om die teenwoordigheid van enkelstring MIV DNS te bepaal. 'n Laag van koolstof nanovesels is gekies as koppelvlak, met DNS haarnaald probes daaraan geheg deur middel van 'n molekulere enkellaag. Die enkellaag is gevorm deur middel van goud-tiol bindings, waar die goud deur 'n plasma deponeeringsproses op die nanovesels neergele is. Fluoressente merkers en gefokusde fluoressensie mikroskopie is gebruik om die suksesvolle aanhegting van die haarnaald probes te ondersoek en verifieer. 'n Hoe-akkuraatheid en laestroom meetbaan is ontwerp om die weerstandsverandering in die nanovesel laag waar te neem gedurende die hibridiseringsproses. 'n Gebruikersvriendelike grafiese koppelvlak is ook ontwerp om alle gemete data aan 'n gebruiker te vertoon en te stoor vir latere verwerking. Alle elektroniese toetse het gebruik gemaak van ferroseen-germekte haarnaald probes omdat daar geglo word dat elektrochemiese reaksies in biosensors verhoog word deur ferroseen aanpassings. Die ontwerpte haarnaald probes het soos verwag opgetree gedurende fluoressensiegebaseerde toetse, maar geen ooreenstemmende elektriese verandering kon gemeet word nie. Verskeie verwerkingsprosesse is ondersoek om die waarskynlikheid dat MIV DNS opgemerk word te verhoog, maar daar is gevind dat die sensor die toevoeging van 'n monster oplossing kon meet, maar nie noodwendig die teenwoordigheid van MIV DNS nie. Verskeie optimerings en alternatiewe oplossings is voorgestel en daar word geglo dat dit baie moontlik is om met klein veranderings 'n effektiewe weerstand sensor vir MIV DNS te realiseer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103493
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