Citation: Wohl, I.; Sajman, J.; Sherman, E. Cell Surface Vibrations Distinguish Malignant from Benign Cells. Cells 2023, 12, 1901. https:// doi.org/10.3390/cells12141901 Academic Editor: Michael F. Olson Received: 23 June 2023 Revised: 14 July 2023 Accepted: 19 July 2023 Published: 21 July 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). cells Article Cell Surface Vibrations Distinguish Malignant from Benign Cells Ishay Wohl , Julia Sajman and Eilon Sherman * Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel; ishaywohl@gmail.com (I.W.); julia.sajman@mail.huji.ac.il (J.S.) * Correspondence: eilon.sherman@mail.huji.ac.il Abstract: The mechanical properties of living cells, including their shape, rigidity, and internal dynamics play a crucial role in their physiology and pathology. Still, the relations between the physiological cell state and its rigidity and surface vibrations remain poorly understood. Here, we have employed AFM measurements on T cells and found a negative relation between cell surface stiffness and its vibrations. Blocking T-type Ca ++ -channels using Mibefradil reduced cortical actin tension in these cells and enhanced their membrane vibrations and dissipation of intracellular mechanical work to the cell surroundings. We also found increased vibrations of cell membranes in five different malignant cells lines derived from T cell leukemia, lung, prostate, bladder, and melanoma cancers, as compared to their corresponding benign cells. This was demonstrated by utilizing TIRF microscopy in single cells and dynamic laser speckles measurements in an in vitro model of multiple cells in a tissue. Our results show that cell membrane vibrations and dissipation of mechanical work are higher in malignant cells relative to benign cells. Accordingly, these properties may be used to detect and monitor cellular and tissue malignancies. Keywords: stiffness; vibrations; mechanical work; dissipation; malignancy 1. Introduction The mechanical properties of living cells, including their shape, rigidity, and internal dynamics, play a crucial role in cell physiology and pathology [1,2]. The mechanical response of the cell generally depends on its three main mechanical components: the cytoskeleton, the nucleus, and the cytoplasm. The cell cytoskeleton largely determines its shape and rigidity [2,3]. An important component of the cell cytoskeleton is the dense cortical actin mesh at the outer borders of the cytoskeleton. That structure is mechanically connected to the inner surface of the cell membrane [4]. This actin mesh elasticity and cross-linking control the overall cell stiffness [4]. More specifically, interactions of molecular motors such as kinesin, dynein, and myosin II with the cytoskeleton produce forces and mechanical work that significantly affect the motion and diffusion of intracellular constituents [5]. These forces cause a direct motion of cell’s constituents such as organelles (the power of motion in this case is around 2; i.e., <Δr 2 >~CΔt α , where α = 2). A dissipative part of that intracellular mechanical work is generated by the incoherent component of the action of those molecular motors [5]. That dissipative part contributes to significant vibrations of the cytoskeleton elastic mesh. In turn, those vibrations have a major impact on the active intracellular diffusivity [6] (the power of motion/diffusion in this case is less than 2; i.e., α < 2) and intracellular organization [7]. The balance between cellular elasticity and intracellular mechanical work influences the motion of intracellular content, and thus significantly affects the dynamics and organi- zation of the cell’s constituents [6,7]. While intracellular elasticity increases cellular stiffness, dis-homogeneity of intra-organelles content and reduces intracellular constituent motion, Cells 2023, 12, 1901. https://doi.org/10.3390/cells12141901 https://www.mdpi.com/journal/cells