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Plasmonic nanostructured sensors for malaria biosensing
Thesis (PhD)--Stellenbosch University, 2026.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867614126445953024 |
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| access_status_str | Open Access |
| author | Kiyumbi, Amos Sospeter |
| author2 | Tame, M. S. |
| author_browse | Kiyumbi, Amos Sospeter Tame, M. S. |
| author_facet | Tame, M. S. Kiyumbi, Amos Sospeter |
| author_sort | Kiyumbi, Amos Sospeter |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2026. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/136193 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:47:05.324Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/136193 Plasmonic nanostructured sensors for malaria biosensing Kiyumbi, Amos Sospeter Tame, M. S. Bosman, G. W. Stellenbosch University. Faculty of Science. Dept. of Physics. Thesis (PhD)--Stellenbosch University, 2026. Kiyumbi, A. S. 2026. Plasmonic nanostructured sensors for malaria biosensing. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/f3259fdf-c165-4d61-911a-86e65717c7c7 Recently, there has been growing interest in the development of new types of biosensors for infectious disease diagnostics, particularly for malaria, due to the need to overcome the limitations of conventional methods, such as sensitivity and specificity. Optical biosensors offer a rapid, sensitive, and specific means of detecting malaria biomarkers, making them a valuable tool for timely diagnosis and effective treatment. In this dissertation, we investigate the detection of low concentrations of a malaria biomarker, namely plasmodium lactate dehydrogenase (pLDH), in a buffer solution using plasmonic-based optical biosensors made from metasurfaces comprised of gold and aluminium nanohole arrays. The protein pLDH is a key enzyme in the glycolytic pathway of malaria parasites. We study the sensitivity and limit of detection of these nanostructured plasmonic sensors and compare them with standard biosensors such as the enzyme-linked immunosorbent assay. In the first part of this dissertation, we theoretically study a non-functionalized surface plasmon resonance (SPR) sensor using the software COMSOL Multiphysics. The sensor is made of equal distance periodic circular nanoholes on a gold planar surface. It is an array of nanoholes patterned in a 100 nm thick gold film, where the diameter of the nanoholes is 150 nm and the center-to-center separation is 400 nm. We consider the bulk sensing of analytes whose refractive index n represents different malaria infection stages, that is, the normal stage n = 1.408, the ring stage n = 1.396, the trophozoite stage n = 1.381 and the schizont stage n = 1.371. We show that, in terms of refractive index unit (RIU), a limit of detection (LOD) of 1.00 × 10−4 RIU can be achieved. In the second part, we develop an effective microscopic model for plasmonic sensing of the malaria biomarker pLDH with a functionalized gold metasurface. Using Maxwell Garnett effective medium theory, we link the refractive index of the pLDH adsorbed layer on the sensor surface to the bulk concentration in the buffer. The effective model reflects the combined optical properties of the biochemical matrix, bound pLDH, and buffer medium, which allows one to predict the functionalized sensor response. The model accurately predicts binding interactions due to changes in pLDH concentration on the sensor surface. Using the model, we calculated the sensor sensitivity and the theoretical LOD. The lowest LOD calculated was 0.02 nM of pLDH (equivalent to 0.70 ng/mL). The model is quite general, and can be used to interpret and predict the optical response of any functionalized SPR biosensor, not only metasurface based sensors. It may therefore be useful in guiding the design of effective biosensors in real clinical settings. In the third part, we perform an actual biosensing experiment to detect pLDH in a buffer solution. This part reports on the design, functionalization, probing, and experimental performance of an aluminium-metasurface biosensor to detect pLDH. The majority of plasmonic-based biosensors have been fabricated using gold, which is why we studied it in detail in the first two parts of this work. However, a more cost-effective alternative plasmonic material for commercialization is aluminium. The aluminium sensor is based on SPR and, similar to the gold metasurface biosensors studied theoretically, it operates based on extraordinary optical transmission resonance shifts. The sensor has an LOD of 1.3 nM of pLDH (equivalent to 45.6 ng/mL) obtained by intensity detection interrogation. This optical biosensor offers a better LOD than conventional methods for detecting active infections and may provide an economical option for early and asymptomatic malaria detection in endemic areas. Doctoral 2026-04-24T12:32:13Z 2026-04-24T12:32:13Z 2026-03 Thesis https://scholar.sun.ac.za/handle/10019.1/136193 en Stellenbosch University 118 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Kiyumbi, Amos Sospeter Plasmonic nanostructured sensors for malaria biosensing |
| title | Plasmonic nanostructured sensors for malaria biosensing |
| title_full | Plasmonic nanostructured sensors for malaria biosensing |
| title_fullStr | Plasmonic nanostructured sensors for malaria biosensing |
| title_full_unstemmed | Plasmonic nanostructured sensors for malaria biosensing |
| title_short | Plasmonic nanostructured sensors for malaria biosensing |
| title_sort | plasmonic nanostructured sensors for malaria biosensing |
| url | https://scholar.sun.ac.za/handle/10019.1/136193 |
| work_keys_str_mv | AT kiyumbiamossospeter plasmonicnanostructuredsensorsformalariabiosensing |