University Greifswald, Greifswald, Germany
Mechanocytometry Session: Friday, October 1st, 2021: 09:00am-10:30am
Role of normal forces mediated by methyl cellulose in cell mechanical assays
Cell mechanical assays, such as Real-Time Deformation Cytometry (RT-DC), have proven to give insight into cells cytoskeletal structure for diagnostic applications. Translating the observed cell deformation to mechanical parameters, e.g. cellular Young’s modulus, is key for understanding underlying physiological effects. In RT-DC strain on co-flowing cells is typically mediated by an aqueous solution of Methyl cellulose (MC) which is known to posses pronounced non-Newtonian behavior leading to cell shearing and additional normal forces. To shed light on the relation between flow profile and the distribution of shear and normal stress we utilize micrometer resolution particle image velocimetry. Small tracer particles are introduced and follow the flow profile faithfully. Observing the motion of the entrained tracer particles reveals that the flow profile of MC solution deviates substantially from a simple Poiseuille flow due to outward directed normal forces. In steady-state MC develops a plug flow, with a steep velocity drop at the channel wall. Our findings suggest that MC undergoes a shear rate induced sol-gel phase transition. Consequently, in steady-state a significant shear rate is localized only in close vicinity to the channel wall minimizing the strain on the cells throughout the channel core.