Combining constitutive materials modeling with atomic force microscopy to understand the mechanical properties of living cells

doi:10.1073/pnas.082520599

Combining constitutive materials modeling with atomic force microscopy to understand the mechanical properties of living cells

^*Lawrence Livermore National Laboratory, Livermore, CA 94550; ^‡Department of Engineering Mechanics, University of Nebraska, Lincoln, NE 68588; and ^§Biometrology, Incorporated, 851 West Midway Avenue, Alameda, CA 94501

Edited by Calvin F. Quate, Stanford University, Stanford, CA, and approved February 21, 2002 (received for review October 1, 2001)

Abstract

The goal of this work is to study the properties of living cells and cell membranes by using atomic force microscopy. During atomic force microscopy (AFM) measurement, there is a strong mechanical coupling between the AFM tip and the cell. The purpose of this paper is to present a model of the overall mechanical response of the cell that allows us to separate out the mechanical response of the cell from the local surface interactions we wish to quantify. These local interactions include recognition (or binding) events between molecules bound to an AFM tip (e.g., an antibody) and molecules or receptors on the cell surface (e.g., the respective antigen). The computational model differs from traditional Hertzian contact models by explicitly taking into account the mechanics of the biomembrane and cytoskeleton. The model also accounts for the mechanical response of the living cell during arbitrary deformation. The indentation of a bovine sperm cell is used to test the validity of this model, and further experiments are proposed to fully parameterize the model.

Footnotes

↵ † To whom reprint requests should be addressed at: Materials Research Institute; L-418, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550. E-mail: mcelfresh1{at}llnl.gov.
This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “Nanoscience: Underlying Physical Concepts and Phenomena,” held May 18–20, 2001, at the National Academy of Sciences in Washington, DC.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

AFM,

atomic force microscopy;

CSG,

coverslip glass;

TSB,

Tris–saline buffer;

F(d),

force–distance