Biophysical Study of Babesia Infected Red Blood Cell using Diffraction Phase Microscopy

Abstract

Babesiisa microti is a protozoan parasite which causes a tick-borne zoonotic disease through blood meditated infection. Conventionally, it is hard to detect the location of parasite infection inside a host blood cell, its progress and physical properties simultaneously with invasive staining method. Thus, we present the biophysical study of Babesia infected red blood cell (RBC) using non-invasive diffraction phase microscopy (DPM) (1, 2). DPM is a quantitative phase imaging technique employing a common-path laser interferometry that measures dynamics of biological samples with nanometer sensitivity. In addition, three -dimensional refractive-index map is also measured simply by tomographic DPM reconstruction with various incident illumination angles (3). Since the hemoglobin is a major optical contrast inside a RBC, the refractive- index map allows visualizing the babesia- infected sites, and that it can be used to determine the infection stage. Secondly, the dynamic membrane fluctuations of RBCs, measured by DPM, are analyzed to address the cell deformability by Babesia infection. Other physiological characteristics such as morphology and dry mass, which were not revealed in conventional method, are also investigated. These results lead us to non-invasively and quantitatively investigate new biological insights for internal structures as well as physiological condition of parasite- infected RBC. 1. Park, Y. K., et al. 2006. Diffraction phase and fluorescence microscopy. Optics Express 14:8263-8268. 2. Popescu, G., et al. 2006. Diffraction phase microscopy for quantifying cell structure and dynamics. Optics. Letters. 31:775-777. 3. Park, Y., et al, and S. Suresh. 2008. Refractive index maps and membrane dynamics of human red blood cells parasitized by Plasmodium falciparum. Proceedings of the National Academy of Sciences of the United States of America 105:13730-13735.