Detecting, quantifying and distinguishing malarial species with surface plasmon microscope

In this work we develop a refractive index-based methodology with a surface plasmon microscope to detect, then quantize and eventually differentiate various malarial species in human whole blood. A nanometric flat metal surface can support surface plasmons. The plasmon propagates along the metal surface with a propagation constant that reveals a direct dependency on a refractive index in the optical near field of the surface. This surface plasmon microscope is a sensitive measurement probe for the refractive index with standard deviation ∼10 −4 on the metal surface. Whole blood samples from patients infected with malaria were evaluated. The quantification of unprocessed whole blood infected with 2000 parasites/µl of Plasmodium falciparum and Plasmodium vivax species revealed significant differences in refractive index ∼10 −1 AU. While that with 200 parasites/µl of Plasmodium falciparum and Plasmodium vivax species revealed differences in refractive index ∼ 10 −2 AU. ● The probe can detect refractive indices ∼ 10 −4 RIU. ● Significant changes in refractive index for Plasmodium vivax and Plasmodium falciparum species observed. ● Ability of this probe to detect and distinguish Plasmodium even for low parasitemia (demonstrated for ∼ 60 parasites/μl). ● Simultaneous detection, quantification and distinction of malarial species possible in a label free manner.