Multifractal characterization of morphology of human red blood cells membrane skeleton

The purpose of this paper is to show applicability of multifractal analysis in investigations of the morphological changes of ultra‐structures of red blood cells (RBCs) membrane skeleton measured using atomic force microscopy (AFM). Human RBCs obtained from healthy and hypertensive donors as well as healthy erythrocytes irradiated with neutrons (45 μGy) were studied. The membrane skeleton of the cells was imaged using AFM in a contact mode. Morphological characterization of the three‐dimensional RBC surfaces was realized by a multifractal method. The nanometre scale study of human RBCs surface morphology revealed a multifractal geometry. The generalized dimensions D_q and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of their membrane skeleton organization. Surface characterization was made using areal ISO 25178‐2: 2012 topography parameters in combination with AFM topography measurement. The surface structure of human RBCs is complex with hierarchical substructures resulting from the organization of the erythrocyte membrane skeleton. The analysed AFM images confirm a multifractal nature of the surface that could be useful in histology to quantify human RBC architectural changes associated with different disease states. In case of very precise measurements when the red cell surface is not wrinkled even very fine differences can be uncovered as was shown for the erythrocytes treated with a very low dose of ionizing radiation.     

Atomic force microscopy and cells: Indentation profiles around the AFM tip,cell shape changes,and other examples of experimental factors affecting modeling

We use atomic force microscopy in conjunction with a fluorescence microscope capable of optical sectioning to acquire images of white blood cells while force is applied with the AFM tip. The indentation profile within the cell is compared to the profile of the AFM tip: examples are shown for indentations at the center of the cell which are reasonable matches to the tip profile, and an additional example is shown for an indentation that is on the tilted side of a highly rounded cell and that differs from the tip shape. We also demonstrate that the AFM tip can interact with internal cell structures, we show that the contact area between the cell and the substrate can increase under applied pressure, that the main body of the cell can fuse with the extended lamellipodium, and that the cell can be displaced laterally by the AFM tip. The features illustrated here are relevant to the interpretation of indentation experiments that measure cell elasticity properties, as is discussed briefly. Microsc. Res. Tech. 78:626–632, 2015. © 2015 Wiley Periodicals, Inc.