title: Characterizing single suspended cells by optorheology.
abstract: The measurement of the mechanical properties of individual cells has received much attention in recent years. In this paper we describe the application of optically induced forces with an optical stretcher to perform step-stress experiments on individual suspended fibroblasts. The conversion from creep-compliance to frequency-dependent complex shear modulus reveals characteristic viscoelastic signatures of the underlying cytoskeleton and its dynamic molecular properties. Both normal and cancerous fibroblasts display a single stress relaxation time in the observed time and frequency space that can be related to the transient binding of actin crosslinking proteins. In addition, shear modulus and steady-state viscosity of the shell-like actin cortex as the main module resisting small deformations are extracted. These values in combination with insight into the cells' architecture are used to explain their different deformability. This difference can then be exploited to distinguish normal from cancerous cells. The nature of the optical stretcher as an optical trap allows easy incorporation in a microfluidic system with automatic trapping and alignment of the cells, and thus a high measurement throughput. This carries the potential for using the microfluidic optical stretcher to investigate cellular processes involving the cytoskeleton and to diagnose diseases related to cytoskeletal alterations.
authors.affiliation: Institute for Soft Matter Physics, Department of Physics and Geosciences, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany.
authors.forename: Falk
authors.initials: F
authors.lastname: Wottawah
authors.forename: Stefan
authors.initials: S
authors.lastname: Schinkinger
authors.forename: Bryan
authors.initials: B
authors.lastname: Lincoln
authors.forename: Susanne
authors.initials: S
authors.lastname: Ebert
authors.forename: Karla
authors.initials: K
authors.lastname: Müller
authors.forename: Frank
authors.initials: F
authors.lastname: Sauer
authors.forename: Kort
authors.initials: K
authors.lastname: Travis
authors.forename: Jochen
authors.initials: J
authors.lastname: Guck
mesh_terms: D000818:Animals; D002460:Cell Line; D002477:Cells; D051379:Mice; D044085:Microfluidics; D012212:Rheology