Directional Migration of Vascular Smooth Muscle Cells
Guided by a Molecule Weight Gradient of Poly(2-hydroxyethyl methacrylate)
Brushes
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Abstract
Directional
migration of cells mediated by gradient cues <i>in vitro</i> can mimic the corresponding biological events <i>in vivo</i> and thereby provides a way to disclose the cascade
responses in tissue regeneration processes and to develop novel criteria
for design of tissue-inductive biomaterials. In this work, a molecular
weight gradient of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes
with a thickness ranging from 3 to 30 nm and slopes of 0.8–3.2
nm/mm were fabricated by using surface-initiated atom transfer radical
polymerization (ATRP) and a dynamically controlled reaction process.
The PHEMA gradients were characterized by X-ray photoelectron spectrometry
(XPS) and ellipsometry. The adhesion number, spreading area, adhesion
force, and expression of focal adhesion and actin fibers of vascular
smooth muscle cells (VSMCs) decreased along with the increase of the
PHEMA brushes length. The VSMCs exhibited preferential orientation
and enhanced directional migration toward the direction of reduced
PHEMA thickness, whose extent was dependent on the gradient slope
and polymer thickness. Most of the cells were oriented, and 87% of
the cells moved directionally at the optimal conditions