Extracellular microenvironment is highly dynamic where spatiotemporal regulation of cell-instructive cues such as matrix topography tightly regulates cellular behavior. Recapitulating dynamic changes in stimuli-responsive materials has become an important strategy in regenerative medicine to generate biomaterials which closely mimic the natural microenvironment. Here, light responsive liquid crystal polymer networks are used for their adaptive and programmable nature to form hybrid surfaces presenting micrometer scale topographical cues and changes in nanoscale roughness at the same time to direct cell migration. This study shows that the cell speed and migration patterns are strongly dependent on the height of the (light-responsive) micrometer scale topographies and differences in surface nanoroughness. Furthermore, switching cell migration patterns upon in situ temporal changes in surface nanoroughness, points out the ability to dynamically control cell behavior on these surfaces. Finally, the possibility is shown to form photoswitchable topographies, appealing for future studies where topographies can be rendered reversible on demand.

Beyond forming bone, osteoblasts play pivotal roles in various biologic processes, including hematopoiesis and bone metastasis. Extracellular vesicles (EVs) have been implicated in intercellular communication via transfer of proteins and nucleic acids between cells. We focused on the proteomic characterization of nonmineralizing (NMOBs) and mineralizing (MOBs) human osteoblast (SV-HFOs) EVs and investigated their effect on human prostate cancer (PC3) cells by microscopic, proteomic, and gene expression analyses. Proteomic analysis showed that 97% of the proteins were shared among NMOB and MOB EVs, and 30% were novel osteoblast-specific EV proteins. Label-free quantification demonstrated mineralization stage-dependent 5-fold enrichment of 59 and 451 EV proteins in NMOBs and MOBs, respectively. Interestingly, bioinformatic analyses of the osteoblast EV proteomes and EV-regulated prostate cancer gene expression profiles showed that they converged on pathways involved in cell survival and growth. This was verified by in vitro proliferation assays where osteoblast EV uptake led to 2-fold increase in PC3 cell growth compared to cell-free culture medium-derived vesicle controls. Our findings elucidate the mineralization stage-specific protein content of osteoblast-secreted EVs, show a novel way by which osteoblasts communicate with prostate cancer, and open up innovative avenues for therapeutic intervention.-Morhayim, J., van de Peppel, J., Demmers, J. A. A., Kocer, G., Nigg, A. L., van Driel, M., Chiba, H., van Leeuwen, J. P. Proteomic signatures of extracellular vesicles secreted by nonmineralizing and mineralizing human osteoblasts and stimulation of tumor cell growth. FASEB J. 29, 274-285 (2015). www.fasebj.org

Mesenchymal stem cells (MSCs) are intensively investigated for regenerative medicine applications due to their ease of isolation and multilineage differentiation capacity. Hence, designing instructive microenvironments to guide MSC behavior is important for the generation of smart interfaces to enhance biomaterial performance in guiding desired tissue formation. Supported lipid bilayers (SLBs) as cell membrane mimetics can be employed as biological interfaces with easily tunable characteristics such as biospecificity, mobility, and density of predesigned ligand molecules. Arg-Gly-Asp (RGD) ligand functionalized SLBs are explored for guiding human MSC (hMSC) adhesion and differentiation by studying the effect of changes in ligand density and mobility. Cellular and molecular analyses show that adhesion occurs through specific interactions with RGD ligands where the extent is positively correlated to changes in ligand density. Furthermore, cell area is significantly regulated by ligand density on ligand-mobile SLBs when compared to ligand-immobile SLBs. Finally, the osteogenic differentiation capacity of hMSCs is positively correlated to ligand density on ligand-mobile SLBs indicating that regulation of cell spreading is linked to cell differentiation capacity. These results demonstrate that hMSC behavior can be directed on SLBs by molecular design and presents SLBs as versatile platforms for future engineering of smart biomaterial coatings.

Light responsive materials that are able to change their shape are becoming increasingly important. However, preconfigurable bistable or even multi‐stable visible light responsive coatings have not been reported yet. Such materials will require less energy to actuate and will have a longer lifetime. Here, it is shown that fluorinated azobenzenes can be used to create rewritable and pre‐configurable responsive surfaces that show multi‐stable topographies. These surface structures can be formed and removed by using low intensity green and blue light, respectively. Multistable preconfigured surface topographies can also be created in the absence of a mask. The method allows for full control over the surface structures as the topographical changes are directly linked to the molecular isomerization processes. Preliminary studies reveal that these light responsive materials are suitable as adaptive biological surfaces.

There is an increasing interest in coupling reactions for cross-linking of cell-encapsulating hydrogels under biocompatible, chemoselective, and tunable conditions. Inspired by the biosynthesis of luciferins in fireflies, here we exploit the cyanobenzothiazole-cysteine (CBT-Cys) click ligation to develop polyethylene glycol hydrogels as tunable scaffolds for cell encapsulation. Taking advantage of the chemoselectivity and versatility of CBT-Cys ligation, a highly flexible gel platform is reported here. We demonstrate luciferin-inspired hydrogels with important advantages for cell encapsulation applications: (i) gel precursors derived from inexpensive reagents and with good stability in aqueous solution (>4 weeks), (ii) adjustable gel mechanics within physiological ranges (E = 180−6240 Pa), (iii) easy tunability of the gelation rate (seconds to minutes) by external means, (iv) high microscale homogeneity, (v) good cytocompatibility, and (iv) regulable biological properties. These flexible and robust CBT-Cys hydrogels are proved as supportive matrices for 3D culture of different cell types, namely, fibroblasts and human mesenchymal stem cells. Our findings expand the toolkit of click chemistries for the fabrication of tunable biomaterials.