محبوبه مهرباني

In recent years, identifying cancerous transformations in living cells based on their mechanical properties an‎d surface topography has gained attention as a non-invasive method for cancer diagnosis. Atomic force microscopy, with its nanometric precision an‎d capability to operate under physiological conditions, serves as a powerful tool for studying cells. However, challenges such as slow scanning speed an‎d the potential risk of damaging living tissues still exist. To overcome these limitations, manipulation process modeling has been proposed to determine the permissible force range for non-damaging manipulation. In this study, to enhance the accuracy of cell manipulation modeling in liquid environments, the effects of three key parameters—friction, folding factor, an‎d adhesion—were analyzed. Given the increasing incidence of breast cancer an‎d hematological malignancies in recent years, healthy an‎d cancerous breast cells, healthy an‎d cancerous blood cells, as well as healthy red blood cells an‎d minor thalassemic red blood cells were studied using atomic force microscope. Contact mechanics modeling an‎d experimental testing were conducted on these samples for a more precise analysis of the contact behavior of these cells, various contact mechanics theories were applicated. Additionally, red blood cell contacts mechanics simulations using COMSOL software have been employed to validate the mathematical modeling, an‎d the optimal positioning angle of the two AFM probes has also been investigated using this method. The results indicated that at the nanometric scale, due to negligible adhesive forces an‎d the small Tabor number, the Derjaguin-Muller-Toporov theory provides a more accurate description compared to the Johnson-Kendall-Roberts theory. However, in cases of significant cellular deformation, the Tatara an‎d Chang contact theories offer higher accuracy. Additionally, V-shaped cantilevers were found to be a more appropriate choice for biological cell manipulation due to their high flexibility. In the dual-probe configuration with a 120-degree angle, it has reduced the indentation depth into the cell by up to 26% for each probe compared to the single-probe mode. Furthermore, environmental property analysis demonstrated that with increasing density an‎d viscosity of the surrounding medium, the indentation depth under an identical contact force increase. For cell sample preparation, two methods—"fresh" an‎d "stamp" state—were employed to prevent unwanted cell aggregation. The results showed that breast an‎d white blood cell malignancy reduced their dimensions. For example, leukemia cells in "stamp" an‎d "fresh" state conditions were at least 45% an‎d 48% smaller, an‎d at most 61% an‎d 63% smaller compared to healthy white blood cells, respectively. Moreover, while breast cell malignancy decreased its elastic modulus, red blood cell malignancy increased it. The elastic modulus of leukemia cells in "stamp" an‎d "fresh" state conditions was measured as 1.45 kPa an‎d 0.85 kPa, respectively, showing an increase of 23% an‎d 5% compared to healthy white blood cells. Importantly, cancerous transformation did not induce significant changes in the topography of breast an‎d white blood cells. Additionally, leukemia cells in the "fresh state" condition exhibited greater deformability, leading to a 17% lower elastic modulus than in the "stamp state" condition. Moreover, the adhesion force an‎d work of adhesion of leukemia cells were significantly higher in "fresh state" compared to "stamp state". Overall, these investigations revealed that while cancerous transformation does not notably alter cell topography, mechanical characterization of cells provides a more suitable approach for assessing their health status.

ميكروسكوپ نيروي اتمي دو سوزن , مكانيك تماس , نانومنيپوليشن , نانوذرات زيستي , محيط سيال

double-tip atomic force microscope , contact mechanics , fluid environment , biological nanoparticles

Mahboube Mehrabani

Dr. Moharam Habibnejad Korayem