A. S. Kiyumbi | Searcharxiv

arXiv2026

Experimental plasmonic sensing of malaria using an aluminum metasurface

A wide range of methods currently exist for testing the presence of malaria, each with its own advantages and disadvantages. New technologies are urgently needed to develop more effective diagnosis tools to fight and eradicate malaria. Optical biosensors that employ surface plasmon resonance (SPR) techniques are a promising category of devices for detecting malaria biomarkers. One such biomarker is plasmodium lactate dehydrogenase (pLDH), a protein produced during the life cycle of the malaria parasite, which is a metabolic enzyme found in all plasmodium species, including the most widespread falciparum. This work reports on the design, probing, and experimental performance of an optical biosensor for detecting pLDH based on SPR and extraordinary optical transmission. The biosensor is composed of an aluminum metasurface made from an array of nanoholes. The sensor operates in the visible spectral region and achieves label-free sensing of plasmodium falciparum LDH (pfLDH) spiked in phosphate-buffered saline. The sensor has a spectral sensitivity of 360 nm/RIU and an LOD of 1.3 nM, equivalent to 45.6 ng/mL of pfLDH. This type of optical biosensor may offer a cost-effective and high sensitivity method for active infection diagnosis.

physics.med-ph↗

arXiv2026

An effective microscopic model for plasmonic sensing of malaria

Malaria remains a major health threat in low-resource regions and rapid diagnostic tests often lack the sensitivity required for early detection. To address this and help establish more sensitive testing devices, we develop a predictive microscopic model for plasmonic biosensing using metasurfaces. Specifically, we consider the detection of plasmodium lactate dehydrogenase (pLDH), a well-known malaria biomarker. An example metasurface is studied to showcase the effective microscopic model - it consists of a gold nanohole array (150nm film; 150nm diameter; 400nm period) and the biochemistry above it is modelled as stacks of closely packed adlayers. Using Maxwell Garnett effective medium theory we link the refractive index of the pLDH biomarker adsorbed layer on top of the metasurface to the bulk concentration of pLDH in the buffer. This effective microscopic model accounts for the combined optical properties of the biochemistry matrix, bound pLDH and the buffer medium. By simulating the sensor using the finite element method and an approximate analytical method, we show that the effective model allows one to determine the sensor response, predict binding interactions, and quantify concentration changes on the sensor surface. We then calculate the sensor sensitivity for our example metasurface and its theoretical limit of detection (LOD). The lowest LOD calculated based on the model is 0.02nM of pLDH, equivalent to 0.7ng/mL, which is a 30 times improvement over current rapid diagnostic tests. While this improvement in performance is highly promising, further work on transferring the ideal theory developed here to field-tested empirical performance will be required. The effective microscopic model we introduce is quite general and the framework developed offers a broadly applicable tool for the design and optimization of other types of highly sensitive plasmonic biosensors.

physics.optics↗