Development of a Novel Biosensor Based on Localized Surface Plasmon Resonance Using Gold Nanoparticles for Detection of Malaria Antigens in Nigerian Clinical Settings

Malaria remains a leading cause of mortality in Nigeria, claiming over 100,000 lives annually, with rapid and accurate point-of-care diagnosis critical for effective case management in low-resource clinical settings. Localized surface plasmon resonance biosensors exploiting the wavelength-shifting optical response of gold nanoparticles to surface binding events offer a label-free, instrument-light detection platform potentially well suited to Nigerian healthcare settings. This research develops an original localized surface plasmon resonance biosensor for detection of Plasmodium falciparum histidine-rich protein-2 antigen, the primary malaria diagnostic target, using functionalized gold nanoparticles synthesized and characterized at the University of Ibadan, Oyo State, South West Nigeria. The theoretical foundation derives the relationship between antigen binding-induced changes in the local dielectric environment around gold nanoparticles and the resulting plasmon resonance wavelength shift using an extended Mie theory incorporating a core-shell model for the bioconjugated nanoparticle. This analytical model predicts sensor wavelength sensitivity as a function of nanoparticle size, shape, and ligand shell thickness. Nanoparticles of 20, 40, and 60 nm diameter were synthesized by citrate reduction and functionalized with anti-HRP2 monoclonal antibodies. Plasmon resonance spectra were measured before and after antigen incubation using a fiber optic microspectrometer to quantify wavelength shift as a function of antigen concentration. A linear calibration range of 0.5 to 100 ng/mL was established, with a detection limit of 0.35 ng/mL, below the clinical positivity threshold. Clinical validation against 80 malaria patient and control blood samples from the University College Hospital Ibadan achieved 94 percent sensitivity and 96 percent specificity relative to PCR gold standard diagnosis. Keywords: plasmon resonance, biosensor, malaria, gold nanoparticles, point-of-care diagnostics