Fluorescence laser tracking microrheology

Microrheology allows for the characterization of a material stress-strain relationship in sample volumes of less than a milliliter that are particularly adapted to biological studies. It enables one to elucidate the mechanical properties of the cytoskeleton of the cell, which are crucial for understanding biological responses such as cell migration and structural dynamics. To gain insight in this field, we choose to monitor the frequency-dependent complex shear modulus G*(ω) by a nondestructive method that does not incorporate any foreign body into the cell. This method of laser tracking extracts information from the Brownian motion of individual spherical particles embedded in the viscoelastic cytoskeletal mesh. We will use a differential detection system in a novel laser device to ascertain the trajectory of the particle with subnanometer and near-microsecond resolution, information that can be related to G*(ω). This technique provides a way to quantify the viscoelastic behavior of the cell with wide bandwidth (five decades of frequencies). Additionally, incorporating fluorescence in this assay will allow us to discriminate organelles or cellular locations of interest.