The Use of Microrheology in the Study of Cells as Active Materials

Brenton Hoffman
Duke University
Thursday, April 25, 2013
NCSU 136 Monteith Research Center, Centennial Campus| 4:00pm

Passive microrheology techniques, based on the quantification of Brownian fluctuations in soft matter, are often used to study the mechanical properties of polymeric or self-assembled materials. However, in contrast to standard materials, living cells internally generate fluctuating stresses, likely due to the activity of molecular motors and the presence of polymerizing cytoskeletal filaments. Over the last decade, microrheology techniques have been extended to enable the determination of the spectroscopic properties of these active fluctuating forces, providing a new window into both the molecular biology of the cytoskeleton in living cells and the behavior of active materials. Through the use of multiple high-speed microrheology techniques, we have probed cytoskeletal fluctuations over 5 decades in frequency, enabling the separation of Brownian and active fluctuations. Remarkably this data suggests the mechanical behavior of the cytoskeleton is consistent with a simple, theoretically tractable physical description, a system of polar filaments driven by directionally-biased molecular motors.