posted on 2022-02-03, 18:05authored byLina Alhalhooly, Matthew I. Confeld, Sung Oh Woo, Babak Mamnoon, Reed Jacobson, Shrinwanti Ghosh, Jiha Kim, Sanku Mallik, Yongki Choi
Integrin-targeting arginine–glycine–aspartic
acid
(RGD)-based nanocarriers have been widely used for tumor imaging,
monitoring of tumor development, and delivery of anticancer drugs.
However, the thermodynamics of an RGD–integrin formation and
dissociation associated with binding dynamics, affinity, and stability
remains unclear. Here, we probed the binding strength of the binary
complex to live pancreatic cancer cells using single-molecule binding
force spectroscopy methods, in which RGD peptides were functionalized
on a force probe tip through poly(ethylene glycol) (PEG)-based bifunctional
linker molecules. While the density of integrin αV receptors on the cell surface varies more than twofold from cell
line to cell line, the individual RGD–integrin complexes exhibited
a cell type-independent, monovalent bond strength. The load-dependent
bond strength of multivalent RGD–integrin interactions scaled
sublinearly with increasing bond number, consistent with the noncooperative,
parallel bond model. Furthermore, the multivalent bonds ruptured sequentially
either by one or in multiples, and the force strength was comparable
to the synchronous rupture force. Comparison of energy landscapes
of the bond number revealed a substantial decrease of kinetic off-rates
for multivalent bonds, along with the increased width of the potential
well and the increased potential barrier height between bound and
unbound states, enhancing the stability of the multivalent bonds between
them.