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Fast Fluorescence Laser Tracking Microrheometry, I: Instrument Development

Maxine Jonas ^*, Hayden Huang , Roger D. Kamm ^*  and Peter T. C. So ^* 

^* Departments of Biological Engineering and Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; and Brigham and Women's Hospital, Boston, Massachusetts

Correspondence: Address reprint requests to Maxine Jonas, E-mail: jonas_m{at}mit.edu.

To gain insight into cellular mechanotransduction pathways, we have developed a fluorescence laser tracking microrheometer (FLTM) to measure material rheological features on micrometer length scales using fluorescent microspheres as tracer particles. The statistical analysis of the Brownian motion of a particle quantifies the viscoelastic properties of the probe's environment, parameterized by the frequency-dependent complex shear modulus G*(). This FLTM has nanometer spatial resolution over a frequency range extending from 1 Hz to 50 kHz. In this work, we first describe the consecutive stages of instrument design, development, and optimization. We subsequently demonstrate the accuracy of the FLTM by reproducing satisfactorily the known rheological characteristics of purely viscous glycerol solutions and cross-linked polyacrylamide polymer networks. An upcoming companion article will illustrate the use of FLTM in studying the solid-like versus liquid-like rheological properties of fibroblast cytoskeletons in living biological samples.

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				M. Jonas, H. Huang, R. D. Kamm, and P. T. C. So Fast Fluorescence Laser Tracking Microrheometry, II: Quantitative Studies of Cytoskeletal Mechanotransduction Biophys. J., July 15, 2008; 95(2): 895 - 909. [Abstract] [Full Text] [PDF]