Magnetic Tweezer System Development Probing mechanical properties across multiple scales Jason Sherfey Senior BME, Vanderbilt University Advisor: Dr. Franz Baudenbacher

Force displacement measurements on magnetic beads linked to the cell surface through E-Cadherin 1 nN 1 2 3 displacement [mm] Time [s] F T=0 s T=1.5 s Fit to Mechanical Analog Extract Model parameter

Force-Displacement Curves MDCK cells Wild-type P120 Knockout

Viscosity (Pa-s-m) N = 10

Elasticity (Pa-m) N = 10

Relaxation Time (s) N = 10

Viscosity (Pa-s-m) Elasticity (Pa-m) Relaxation Time (s) p = 0.364 0.0020 0.0044 Wild-type MDCK 0.0019 0.0038 P120 Knockout MDCK Standard Deviation Mean p = 0.364 No significant difference in WT & KO Viscosities Elasticity (Pa-m) 0.0088 0.0217 Wild-type MDCK 0.0106 0.0118 P120 Knockout MDCK Standard Deviation Mean p = 0.0028 WT Elasticity is significantly larger than KO Relaxation Time (s) 0.0006 0.0421 Wild-type MDCK 0.0725 P120 Knockout MDCK Standard Deviation Mean p = 0.0010 WT Relaxation Time is significantly faster than KO N = 10 cells

Conclusions The stiffness and relaxation time constants are significantly different in p120 knockout and wild-type MDCK cells. 2. The stiffness decreases & relaxation time slows down when p120 expression is reduced in MDCK cells.

Strain Hardening Stiffness (Pa-m) The stiffness of the adhesion protein linker system increases when stress is repeatedly applied. Pull  Wild-type Cell 1 0.0132 2 0.0152 3 0.0193 4 0.0249   Knockout Cell 0.0051 0.0063 0.0081