Towards a Paper-based Biosensor to Distinguish Between Bacterial and Viral Infections

Retief, Johannes Daniel (2019-04)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The increasing threat of antimicrobial resistance has become more prominent in recent years due to strains of common bacteria becoming resistant to the medication used to cure the infections they cause. One of the causes of this problem is the indiscriminate prescription of antibiotics to patients with ambiguous symptoms, breeding antimicrobial resistance. The current management strategy for this problem is to develop more effective means of distinguishing between bacterial and viral infections, and specifically to develop biosensors for this purpose. This project aimed to develop a low-cost paper-based electrochemical transistor sensor to measure and detect the concentration of C-reactive protein in solution, with the goal of the transducers being used to distinguish between bacterial and viral infections in patients with ambiguous symptoms. C-reactive protein is known to be one of a group of proteins with promise in aiding diagnosis of different types of infections, and was chosen for its relatively low cost when compared to the alternatives. An inkjet printing system was developed to aid in the manufacturing process. After extensive modification, a regular desktop inkjet printer was converted to a flatbed configuration and could print structures with a minimum size of 70 μm. Layers of printed material could be aligned with a repeatability of 25 μm. Following successful implementation of the printer, a method was developed to manufacture organic electrochemical transistors onto paper substrates using printed silver electrodes. The transistors were subsequently functionalised and antibodies specific to C-reactive protein were immobilised onto the transducer surface. The transducers were tested and found to respond to CRP concentrations between 2:5 μg.ml-1 and 19.5 ng.ml-1, and the transducers were capable of quantifying protein concentrations over most of the clinically relevant range of concentrations for CRP. This means that the project was successful in developing a low-cost paper-based transducer to potentially aid in the differentiation between viral and bacterial infections.

AFRIKAANSE OPSOMMING: Die hedendaagse probleem van antibakterieële weerstandigheid het onlangs begin om meer aandag te geniet weens die ontluiking van allerdaagse bakterieë wat weerstandigheid ontwikkel het teen die middels wat voorheen gebruik is om hul te bestry. Een van die oorsake van hierdie probleem is die onverskillige voorskrif van antibiotika aan pasiënte met dubbelsinnige simptome, wat antimikrobiese weerstand vererger. Die huidige bestuurstrategieë vir hierdie probleem is om nuwe metodes te ontwikkel waardeur onderskei kan word tussen die oorsake van verskillende soorte infeksies, en spesifiek om nuwe biosensors vir hierdie toepassing te ontwikkel. Die doel van heirdie projek was om ’n laekoste papier-gebaseerde elektrochemiese transistor sensor te ontwikkel om die konsentrasie van C-reaktiewe proteïene in oplossing te meet, met die doel dat die sensors gebruik kan word om tussen bateriële- en virsuinfeksies te onderskei vir pasiënte met dubbelsinnige simptome. Dié keuse van proteïne is gemaak omdat C-reatiewe proteïene deel vorm van groep proteïene met potensiaal om gebruik te word om tussen verskillende infeksiesoorte te onderskei. Van die groep is C-reaktiewe proteïene ook die goedkoopste. ’n Inkspuit drukker is as deel van die projek ontwikkel om sodoende die vervaardiginsproses van die sensors te vergemaklik deur silver elektrodes op papier te duk. Na voltoiïng van die drukker kon strukture tot ’n resolusie van 70 μm gedruk word, en opeenvolgende lae kon tot binne 25 μm van mekaar belyn word. Volgende is ’n vervaardingingsproses ontwikkel waardeur organiese elektrochemiese transistors op papier vervaardig kon word deur van die drukker gebruik te maak. Die vervaardigde transistors is later met teenliggampies bewapen, en getoets. Die transistors was suksesvol darin om konsentrasies van CRP tussen 2:5 μg.ml-1 en 19:5 ng.ml-1 te meet, wat oor die meeste van die bereik van kliniese belang vir CRP strek. Dit beteken dat die projek darin geslaag het om ’n sensor te ontwikkel waarmee daar gepoog kan word om verskillende soorte infeksies van mekaar te onderskei.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106164
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