![]() Light-intensity scattering patterns of (d) healthy RBCs, (e) ring, (f) trophozoite, and (g) schizont stage of Pf-RBCs. (c) The retrieved light scattering pattern of the same cell. (a) Amplitude and (b) phase map of a healthy RBC. From the measured E-field, the far-field scattering intensity is calculated by using a 2-D Fourier transform, This E-field is divided by the E-field without samples to normalize the intensity of the incident beam. 15, 16 For each individual RBC, we measured the E-field E ( x, y t ) = A ( x, y t ) exp, where A ( x, y t ) is the amplitude, and ϕ ( x, y t ) is the phase at a position of ( x, y ) at time t [Figs. To quantitatively measure the E-field maps of Pf-RBCs, we employed diffraction phase microscopy (DPM). 6, 7 The physical principle of FTLS is to measure the complex E-field at the image plane and then numerically propagate this E-field to the far-field scattering plane. We first measured the light-intensity scattering patterns of individual Pf-RBCs by FTLS. We prepared RBCs in four different groups following the standard protocol 14: healthy RBCs, and three parasite maturation stages of Pf-RBCs with 14 to 24 h (late ring stage), 24 to 36 h (trophozoite stage), and 36 to 48 h (schizont stage) after the invasion of the P. We also present dynamic light scattering to characterize transitions from intact membranes of healthy RBCs to modified membranes of Pf-RBCs. We show that the static light scattering patterns of Pf-RBCs are significantly different among different disease states at specific scattering angle windows. In this study, the E-field maps of individual Pf-RBCs were measured and utilized to determined both static and dynamic light scattering distributions. These changes could affect both static and dynamic light scattering of Pf-RBCs. In response to these changes, the characteristic biconcave shape of the RBC is lost, the dynamics of membrane fluctuations are altered, and the Hb concentration in RBC cytoplasm decreases. 12, 13 The parasite causes modifications in the structure, mechanical properties, and biochemical characteristics of the host RBCs. falciparum host RBCs undergo substantial changes. When invaded by the malaria-inducing parasite P. 11 These membrane fluctuations are influenced by mechanical properties of the membrane, and serve as an important indicator of RBC deformability, which in turn plays an important role in the evolution of a number of human diseases. 10 The RBC membrane cortex is sufficiently soft and elastic, and it exhibits dynamic membrane fluctuations driven by both thermal and metabolic energies. ![]() 9 Dynamic light scattering has been used to study the dynamic motion of RBC membranes. 8 Numerical models have been introduced to simulate static light scattering of RBCs. Static light scattering of RBCs has been widely used in flow cytometry for measuring size and hemoglobin (Hb) concentration distribution. Light scattering of red blood cells (RBCs) has also been extensively studied. 5 Recently, Fourier transform light scattering (FTLS), which numerically calculates far-field scattering patterns from the electric field (E-field) measurement, has been developed. 2 Several techniques have been used to study light scattering, including photon correlation spectroscopy, 17 diffuse wave spectroscopy, 3 dynamic scattering microscopy, 4 and single-cell partial-wave spectroscopy. 1 Dynamic (quasielastic) light scattering is the extension of elastic light scattering to study dynamic inhomogeneous systems. Static (elastic) light scattering measures the angular distribution of the scattering intensity to infer structural information of scatterers, which is utilized to probe the structure of living cells or tissues. ![]() Static and dynamic light scattering techniques have been widely used to study the structure and dynamics of scattering objects.
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