Micro- and nano-patterned elastin-like polypeptide hydrogels for stem cell culture
Journal article, 2017
We show that submicron-sized patterns can be imprinted into soft, recombinant-engineered protein
hydrogels (here elastin-like proteins, ELP) by transferring wavy patterns from polydimethylsiloxane
(PDMS) molds. The high-precision topographical tunability of the relatively stiff PDMS is translated to a
bio-responsive, soft material, enabling topographical cell response studies at elastic moduli matching
those of tissues. Aligned and unaligned wavy patterns with mold periodicities of 0.24–4.54 mm were
imprinted and characterized by coherent anti-Stokes Raman scattering and atomic force microscopy.
The pattern was successfully transferred down to 0.37 mm periodicity (width in ELP: 250 50 nm,
height: 70 40 nm). The limit was set by inherent protein assemblies (diameter: 124–180 nm) that
formed due to lower critical solution temperature behavior of the ELP during molding. The width/height
of the ELP ridges depended on the degree of hydration; from complete dehydration to full hydration,
ELP ridge width ranged from 79 9% to 150 40% of the mold width. The surface of the ridged ELP
featured densely packed protein aggregates that were larger in size than those observed in bulk/flat ELP.
Adipose-derived stem cells (ADSCs) oriented along hydrated aligned patterns with periodicities Z0.60 mm
(height Z170 100 nm), while random orientation was observed for smaller distances/amplitudes, as well
as flat and unaligned wavy ELP surfaces. Hence, micro-molding of ELP is a promising approach to create
tissue-mimicking, hierarchical architectures composed of tunable micron-sized structures with nano-sized
protein aggregates, which opens the way for orthogonal screening of cell responses to topography and
cell-adhesion ligands at relevant elastic moduli.