title: A microfabricated platform with hydrogel arrays for 3D mechanical stimulation of cells.
abstract: Cellular microenvironments present cells with multiple stimuli, including not only soluble biochemical and insoluble matrix cues but also mechanical factors. Biomaterial array platforms have been used to combinatorially and efficiently probe and define two-dimensional (2D) and 3D microenvironmental cues to guide cell functions for tissue engineering applications. However, there are few examples of array platforms that include dynamic mechanical forces, particularly to enable stretching of 3D cell-seeded biomaterials, which is relevant to engineering connective and cardiovascular tissues. Here we present a deformable membrane platform that enables 3D dynamic mechanical stretch of arrayed biomaterial constructs. Cell-seeded polyethylene glycol norbornene (PEG-NB) hydrogels were bound to miniaturized deformable membranes via a thiol-ene reaction with off-stoichiometry thiol-ene based polydimethylsiloxane (OSTE-PDMS) as the membrane material. Bonding to OSTE-PDMS enabled the 3D hydrogel microconstructs to be cyclically deformed and stretched by the membrane. As a first demonstration, human mesenchymal stromal cells (MSCs) embedded in PEG-NB were stretched for several days. They were found to be viable, spread in the 3D hydrogels, and exhibited a contractile myofibroblast phenotype when exposed to dynamic 3D mechanical deformation. This platform, which is readily scalable to larger arrays, enables systematic interrogation of the relationships between combinations of 3D mechanobiological cues and cellular responses, and thus has the potential to identify strategies to predictably control the construction of functional engineered tissues.
  
  
  CONCLUSIONS
  Current high-throughput biomaterial screening approaches fail to consider the effects of dynamic mechanical stimulation, despite its importance in a wide variety of regenerative medicine applications. To meet this need, we developed a deformable membrane platform that enables 3D dynamic stretch of arrayed biomaterial constructs. Our approach combines microtechnologies fabricated with off-stoichiometry thiol-ene based polydimethylsiloxane membranes that can covalently bond cell-seeded polyethylene glycol norbornene 3D hydrogels, a model biomaterial with tunable adhesive, elastic and degradation characteristics. As a first demonstration, we show that human mesenchymal stromal cells embedded in hydrogels and subjected to dynamic mechanical stimulation undergo myofibroblast differentiation. This system is readily scaled up to larger arrays, and will enable systematic and efficient screening of combinations of 3D mechanobiological and biomaterial cues on cell fate and function.
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto M5S 3G8, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto M5S 3G9, Canada.
authors.forename: Haijiao
authors.initials: H
authors.lastname: Liu
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto M5S 3G9, Canada.
authors.forename: Jenna
authors.initials: J
authors.lastname: Usprech
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto M5S 3G8, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto M5S 3G9, Canada. Electronic address: sun@mie.utoronto.ca.
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, Toronto M5S 3G8, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto M5S 3G9, Canada. Electronic address: simmons@mie.utoronto.ca.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Simmons
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D019245:Compressive Strength / Q000187:drug effects; D004129:Dimethylpolysiloxanes / Q000737:chemistry / Q000494:pharmacology; D055119:Elastic Modulus / Q000187:drug effects; D020342:Finite Element Analysis; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D008422:Materials Testing; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects; D055616:Microtechnology / Q000379:methods*; D009636:Norbornanes / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D013314:Stress, Mechanical; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013718:Tensile Strength / Q000187:drug effects
chemical_list: D004129:Dimethylpolysiloxanes; D009636:Norbornanes; D013438:Sulfhydryl Compounds; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; C046060:2-norbornene; D011092:Polyethylene Glycols; C013830:baysilon
keywords: Hydrogel; Mechanical stimulation; Mesenchymal stromal cell; Microdevice; Three-dimensional