The 5th Korean-US NanoForum: Nanobiotechnology. Jeju Island, April 17th-19th, 2008
Focal Adhesion Mechanotransduction:Focal Adhesion Mechanotransduction:Cellular Response to Nanoscale Cellular Response to Nanoscale
Mechanical FactorsMechanical Factors
Nathan J. Sniadecki, Ph.D.
Mechanical Engineering DepartmentUniversity of Washington
Seattle, Washington
Mechanotransduction at Focal AdhesionsMechanotransduction at Focal Adhesions
Focal adhesions are force sensitive integrin-receptor complexes (100 nm – 1 μm).
Extracellular Matrix (ECM)
CellActin
Myosin
Extracellular matrix (ECM)
Focal Adhesion (FA)
Structural proteinsStructural proteins link integrins to actin to develop traction force for cellular migration or contraction
Signaling proteinsSignaling proteins activated with integrin-matrix binding and force vinvin
taltal
FAK
tal
p130
Actin
Integrins Integrins
α-ActFAK
Srcpax
Traction Force
External Force
Traction forces or external forces are transduced into biological signals that can regulate cell function
Traction Force Sensor ArrayTraction Force Sensor Array
20 nN
DAPI Actin PDMS Vinculin10 μm
Arrays of flexible microposts to measure traction forces
Made with soft lithography of polydimethlysiloxane (PDMS)
3-μm diameter, 10-μm heightmicroposts
Magnetic MicropostsMagnetic Microposts
Sensor and Actuator SystemSensor and Actuator System• Measure traction forces with microposts
• Apply forces with magnetic nanowires
Cobalt NanowiresCobalt Nanowires• 300 nm diameter, 5-7 μm long• High magnetic moment (µ) along long axis
Nanowire
NanowiresN.J. Sniadecki, et al., PNAS, 2007, 104:114553-8
N.J. Sniadecki, et al., Rev Sci Instr, 2008, 79, 044302
2 2
3 ( )2( )
wMag
w w
L LFL L L Lτ +
=+ +
d
3
3 Eδ δ 64LtrF K π
= =
Bµ ⋅= ⊥τ
Magnetic NanowiresMagnetic Nanowires
2e-
Co2+
Co
Co2+
Co2+
Co2+
Co2+(aq) + 2e- → Co(s)
2 µm
Template
Cobalt Electrodeposition Vibrating Sample Magnetometer
N.J. Sniadecki, et al., PNAS, 2007, 104:114553-8N.J. Sniadecki, et al., Rev Sci Instr, 2008, 79, 044302
FabricationFabrication
1. Lithography
Nanowires magnetically embedded into PDMS mold
4. Deposit Nanowires
2. Develop 5. Encase in PDMS
3. Cast in PDMS 6. Release
SEM Image
EDS Measurement
N.J. Sniadecki, et al., PNAS, 2007, 104:114553-8N.J. Sniadecki, et al., Rev Sci Instr, 2008, 79, 044302
Magnetic StimulationMagnetic Stimulation
N.J. Sniadecki, et al., PNAS, 2007, 104:114553-8
Magnetic actuation for external force
Focal adhesion protein recruitment
Stimulation relaxes traction forces
Spatial ResponseSpatial Response
JumpJump GradualGradual
ControlControl
Magnetic Post
Relaxation occurs at remote sites along cell periphery but not at interior posts
Binomial Analysis:Edge posts have significant loss versus interior posts (p<0.05)Post local to magnetic posts have no significant difference to distal posts (p>0.25)
N.J. Sniadecki, et al., PNAS, 2007, 104:114553-8
NanopostsNanoposts
Sloped-wall cantilever
High Spatial Resolution of Traction Forces
830 nm dia, 3.3 μm tal16 nN/μm
830 nm dia, 3.0 μm tall28 nN/μm
670 nm dia, 3.3 μm tal8 nN/μm
M.T. Yang, N.J. Sniadecki, C.S. Chen, Adv Mat, 2007, 104:114553-8
SUPPORT: National Institutes of Health National Science FoundationThe Hartwell FoundationUW Royalty Research Fund
Nathan J. SniadeckiSangyoon HanAimi Ahmad Shukri
Collaborators:Christopher S. Chen (UPenn)Daniel H. Reich (JHU)
AcknowledgementsAcknowledgements
J. L. Tan, et al., Proc. Nat. Acad. Sci., 2003, 100:1484-1489C. A. Lemmon, et al., Mech. & Chem. Biosystems., 2005, 2(1) 1-16
Micropost Force SensorsMicropost Force Sensors
4
3
3 EdF 64L
K πδ δ
= =
F … Cellular ForceK… Spring Stiffness (32 nN/μm)δ … DisplacementE … Elasticity Modulus of PDMSd … Post diameter (3 μm dia)L … Post Length (10 μm)
Posts deflects as simple cantilever springs:
Microcontact printing:No adhesion blocking: Adhesion only on tips:Post Array:
Fibronectin
Measurements:
PEO
PPO
