title: Stiffness of cancer cells measured with an AFM indentation method.
abstract: The stiffness of cancer cells and its changes during metastasis are very important for understanding the pathophysiology of cancer cells and the mechanisms of metastasis of cancer. As the first step of the studies on the mechanics of cancer cells during metastasis, we determined the elasticity and stiffness of cancer cells with an indentation method using an atomic force microscope (AFM), and compared with those of normal cells. In most of the past AFM studies, Young׳s elastic moduli of cells have been calculated from force-indentation data using Hertzian model. As this model is based on several important assumptions including infinitesimal strain and Hooke׳s linear stress-strain law, in the exact sense it cannot be applied to cells that deform very largely and nonlinearly. To overcome this problem, we previously proposed an equation F=a[exp(bδ)-1] to describe relations between force (F) and indentation (δ), where a and b are parameters relating with cellular stiffness. In the present study, we applied this method to cancer cells instead of Young׳s elastic modulus. The conclusions obtained are: 1) AFM indentation test data of cancer cells can be very well described by the above equation, 2) cancer cells are softer than normal cells, and 3) there are no significant locational differences in the stiffness of cancer cells between the central and the peripheral regions. These methods and results are useful for studying the mechanics of cancer cells and the mechanisms of metastasis.
authors.affiliation: Department of Biomedical Engineering, School of Engineering, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama 700-0001, Japan; Department of Biomedical Engineering, College of Engineering, National Cheng Kung University, Tainan, Taiwan; Division of Bioengineering, Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan. Electronic address: kozaburohayashi@gmail.com.
authors.forename: Kozaburo
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Department of Biomedical Engineering, School of Engineering, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama 700-0001, Japan. Electronic address: pqqdg359@ybb.ne.jp.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Iwata
mesh_terms: D001696:Biomechanical Phenomena; D006367:HeLa Cells; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D009362:Neoplasm Metastasis; D013314:Stress, Mechanical
keywords: Atomic force microscopy (AFM); Cancer cell; Indentation test; Stiffness; Young׳s elastic modulus