Micro- and nano-patterned elastin-like polypeptide hydrogels for stem cell culture

We show that submicron-sized patterns can be imprinted into soft, recombinant-engineered proteinhydrogels (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 abio-responsive, soft material, enabling topographical cell response studies at elastic moduli matchingthose of tissues. Aligned and unaligned wavy patterns with mold periodicities of 0.24–4.54 mm wereimprinted 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) thatformed due to lower critical solution temperature behavior of the ELP during molding. The width/heightof 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 ELPfeatured 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 wellas flat and unaligned wavy ELP surfaces. Hence, micro-molding of ELP is a promising approach to createtissue-mimicking, hierarchical architectures composed of tunable micron-sized structures with nano-sizedprotein aggregates, which opens the way for orthogonal screening of cell responses to topography andcell-adhesion ligands at relevant elastic moduli