Programmable Multivalent DNA-Origami Tension Probes for Reporting Cellular Traction Forces
2018-06-18T00:00:00Z (GMT)
by
Mechanical
forces are central to most, if not all, biological processes,
including cell development, immune recognition, and metastasis. Because
the cellular machinery mediating mechano-sensing and force generation
is dependent on the nanoscale organization and geometry of protein
assemblies, a current need in the field is the development of force-sensing
probes that can be customized at the nanometer-length scale. In this
work, we describe a DNA origami tension sensor that maps the piconewton
(pN) forces generated by living cells. As a proof-of-concept, we engineered
a novel library of six-helix-bundle DNA-origami tension probes (DOTPs)
with a tailorable number of tension-reporting hairpins (each with
their own tunable tension response threshold) and a tunable number
of cell-receptor ligands. We used single-molecule force spectroscopy
to determine the probes’ tension response thresholds and used
computational modeling to show that hairpin unfolding is semi-cooperative
and orientation-dependent. Finally, we use our DOTP library to map
the forces applied by human blood platelets during initial adhesion
and activation. We find that the total tension signal exhibited by
platelets on DOTP-functionalized surfaces increases with the number
of ligands per DOTP, likely due to increased total ligand density,
and decreases exponentially with the DOTP’s force-response
threshold. This work opens the door to applications for understanding
and regulating biophysical processes involving cooperativity and multivalency.