title: Magnetic microposts as an approach to apply forces to living cells.
abstract: Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via microfabricated magnetic posts containing cobalt nanowires interspersed among an array of elastomeric posts, which acted as independent sensors to cellular traction forces. A magnetic field induced torque in the nanowires, which deflected the magnetic posts and imparted force to individual adhesions of cells attached to the array. Using this system, we examined the cellular reaction to applied forces and found that applying a step force led to an increase in local focal adhesion size at the site of application but not at nearby nonmagnetic posts. Focal adhesion recruitment was enhanced further when cells were subjected to multiple force actuations within the same time interval. Recording the traction forces in response to such force stimulation revealed two responses: a sudden loss in contractility that occurred within the first minute of stimulation or a gradual decay in contractility over several minutes. For both types of responses, the subcellular distribution of loss in traction forces was not confined to locations near the actuated micropost, nor uniformly across the whole cell, but instead occurred at discrete locations along the cell periphery. Together, these data reveal an important dynamic biological relationship between external and internal forces and demonstrate the utility of this microfabricated system to explore this interaction.
authors.affiliation: Department of Bioengineering, University of Pennsylvania, 510 Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA 19104, USA.
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Sniadecki
authors.forename: Alexandre
authors.initials: A
authors.lastname: Anguelouch
authors.forename: Michael T
authors.initials: MT
authors.lastname: Yang
authors.forename: Corinne M
authors.initials: CM
authors.lastname: Lamb
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Liu
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Kirschner
authors.forename: Yaohua
authors.initials: Y
authors.lastname: Liu
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Reich
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Chen
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D000818:Animals; D001696:Biomechanical Phenomena; D002448:Cell Adhesion / Q000502:physiology; D018929:Cell Culture Techniques; D003035:Cobalt / Q000737:chemistry; D003599:Cytoskeleton / Q000502:physiology; D005347:Fibroblasts / Q000648:ultrastructure; D005374:Filtration; D007150:Immunohistochemistry; D008280:Magnetics; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D051379:Mice; D041681:NIH 3T3 Cells; D053770:Nanowires / Q000737:chemistry; D016062:Porosity; D013314:Stress, Mechanical; D013997:Time Factors