Micropatterning of bioactive self-assembling gels

Abstract

Microscale topographical features have been known to affect cell behavior. An important target in this area is to integrate top down techniques with bottom up self-assembly to create three-dimensional (3D) patterned bioactive mimics of extracellular matrices. We report a novel approach toward this goal and demonstrate its use to study the behavior of human mesenchymal stem cells (hMSCs). By incorporating polymerizable acetylene groups in the hydrophobic segment of peptide amphiphiles (PAs), we were able to micro-pattern nanofiber gels of these bioactive materials. PAs containing the cell adhesive epitope arginine-glycine-aspartic acid-serine (RGDS) were allowed to self-assemble within microfabricated molds to create networks of either randomly oriented or aligned ~30 nm diameter nanofiber bundles that were shaped into topographical patterns containing holes, posts, or channels up to 8 μm in height and down to 5 μm in lateral dimensions. When topographical patterns contained nanofibers aligned through flow prior to gelation, the majority of hMSCs aligned in the direction of the nanofibers even in the presence of hole microtextures and more than a third of them maintained this alignment when encountering perpendicular channel microtextures. Interestingly, in topographical patterns with randomly oriented nanofibers, osteoblastic differentiation was enhanced on hole microtextures compared to all other surfaces.

Deconstructing the third dimension – how 3D culture microenvironments alter cellular cues

“…These materials typically possess a structural backbone, cell-binding ligands, and a 'cell-friendly' crosslinking mechanism. The most common of these include polyethylene glycol (PEG)-based hydrogels (D in Figure) (Mann et al, 2001;Burdick and Anseth, 2002;Raeber et al, 2005;Miller et al, 2010) and self-assembling peptides (Kisiday et al, 2002;Zhang, 2003;Mata et al, 2009). These gels are highly tunable and often modular in their inclusion of additional functionalities, such as matrix metalloprotease-cleavable domains or growth-factor-binding sites.…”

Peptide conjugate hydrogelators

“…PA molecules have also been chemically cross-linked to improve their toughness using pairs of acetylene groups within the hydrocarbon tail. 179 The 35 acetylene groups align perfectly due to the specific selfassembling of the peptidic segment. Once nanofibres are formed (by physical interactions only), light irradiation can be used to permanently hold the structure together, Figure 11.…”

“…The rate of gelation could be 65 tuned by altering the bulkiness of the amino acids used and the hydrophobicity of the overall peptide sequence. 179 Reproduced by permission of The Royal Society of Chemistry.…”

“…Additionally, Stupp"s group have shown that lithographical techniques can be employed to control the structure of the PA nanofibrous networks. 179,180 By combining lithography with structuredirecting PAs, one can begin to control the nanoparticle 80 morphology of a wide variety of materials, including metals like gold. 181 This latter example, controlling the growth of gold nanoparticles, actually uses a subtly different class of PA as the structure-directing scaffold.…”

Surface Engineering Using Peptide Amphiphiles

“…122 The studied PA is an extended version of the ones studied by Huang et al 123 via nanofibrous PAs may thus provide an excellent platform of biomaterials capable of influencing cytoskeleton organization and associated cell signaling pathways, leading to controlling key stem cell biology.…”