Magnetic Tweezer System Development

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

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

3. Force-Displacement Curves MDCK cells P120 Knockout Wild-type

4. Viscosity (Pa-s-m) N = 10

5. Elasticity (Pa-m) N = 10

6. Relaxation Time (s) N = 10

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

8. 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.

9. Strain Hardening Stiffness (Pa-m) • The stiffness of the adhesion protein linker system increases when stress is repeatedly applied.