Characterization of red blood cells infected by Plasmodium falciparum using optical tweezers

Abstract

The biological function of the human red blood cell (RBC) is primarily determined by its biconcave shape and deformability. However, this property of red blood cells can be disrupted by certain diseases such as malaria. In this article, we studied the mechanical properties of healthy and Plasmodium falciparum-infected human red blood cells (IRBCs) based on the deformation produced by lateral indentation with an optically trapped silica bead. The cell and the microbead float freely in the liquid. The microbead is trapped first and then brought into interaction with the red blood cell. The Boltzmann statistical method was used for force calibration from images captured with a CCD camera. With forces below 80 pN and using the Hertz model, the elasticity modulus (Young's modulus) and the shear modulus for different types of red blood cells were determined. The mean values of the cell shear modulus measured during indentation were $\left(3.37\pm 0.80\right)\mu N/m$ for healthy RBCs and $\left(13.78\pm 2.30\right)\mu N/m$ for infected RBCs. These values, compared to those in the literature, show that these developed approaches are well-suited for studying the mechanical properties of biological cells. These results are important for elucidating information about malaria and for aiding in the development of new diagnostic methods.