Quantification of CD4+ cell count via a nanofibre-based biosensor

Lloyd, Alexander M. (2019-04)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Antigen-substrate binding has been found to cause a change in the resistance of conductive nanofibre substrates. This thesis endeavoured to exploit this phenomenon to produce sensors capable of quantifying CD4+ cell count. Producing nanofibre substrates with appropriate robustness and reproducibility cheaply remains challenging. Previous methods coated non-conductive nanofibres with a non-uniform conductive coating or used carbon nanofibre mats that were very susceptible to mechanical stress. To address these factors that negatively affect reproducibility, intrinsically conductive nanofibres were electrospun from an organic semiconducting polymer through an adaptation of an existing method that decreased the overall material cost. The production process was tuned so as to produce mats with appropriate electrical characteristics and the fibres were aligned in a uniform direction so as to provide directed current paths. These mats were then spun directly onto interdigitated electrodes that had been printed onto semi-hydrophobic paper with silver ink via a modified inkjet printer. By employing appropriate cross-linking chemistry, antibodies were bound to the produced nanofibres. These antibodies served as the biorecognition element for the sensor. The data were analysed and it was evident that the binding event did indeed cause a change in resistance. While this resistance could not be repeatably quantified owing to base variance between electrodes, this thesis lays the groundwork for further research.

AFRIKAANSE OPSOMMING: Daar is al bevind dat antigeen-substraat binding ’n verandering veroorsaak in die weerstand van geleidende nanovesel-substrate. Hierdie tesis het gepoog om hierdie verskynsel in te span met die oog op die vervaardiging van sensors wat in staat is om CD4+ seltelling te kwantifiseer. Om nanovesel-substrate met ’n gepaste vlak van robuustheid en reproduseerbaarheid op ’n goedkoop wyse te produseer, bly ’n uitdaging. Vorige metodes het behels dat nie-geleibare nanovesels bedek word met ’n nie-uniforme geleidende laag, of het gebruik gemaak van koolstof nanovesel matte wat baie vatbaar was vir meganiese stres. Dit was noodsaaklik om hierdie faktore aan te spreek weens hul negatiewe impak op reproduseerbaarheid. Gevolglik is inherent geleidende nanovesels ge-elektrospin uit ’n organiese semi-geleidende polimeer; dit is vermag deur ’n bestaande metode aan te pas op so ’n wyse dat die kostes verbonde daaraan verlaag is. Die proses is verfyn met die doel om matte met die gepaste elektriese eienskappe te produseer en vesels wat in ’n uniforme rigting le, te vervaardig; sodoende is direkte stroompaaie geskep. Hierdie nanoveselmatte is gespin op elektrodes; die elektrodes is met silwer ink gedruk op semi-hidrofobiese papier deur middel van ’n aangepaste injet drukker. Deur die gebruik van kruisbindingchemie is teenliggaampies gebind tot die geproduseerde nanovesels. Hierdie teenliggaampies het gedien as die ”biorecognitionëlement. Uit die analise van die data het dit geblyk dat die bindingproses wel ’n verandering in weerstand tot gevolg gehad het. Alhoewel die weerstand nie herhaalbaar gekwantifiseer kon word nie weens basis afwyking tussen die elektrodes, lê hierdie tesis die grondslag vir verdere navorsing.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106110
This item appears in the following collections: