title: Photoresponsive elastic properties of azobenzene-containing poly(ethylene-glycol)-based hydrogels.
abstract: The elastic modulus of the extracellular matrix is a dynamic property that changes during various biological processes, such as disease progression or wound healing. Most cell culture platforms, however, have traditionally exhibited static properties, making it necessary to replate cells to study the effects of different elastic moduli on cell phenotype. Recently, much progress has been made in the development of substrates with mechanisms for either increasing or decreasing stiffness in situ, but there are fewer examples of substrates that can both stiffen and soften, which may be important for simulating the effects of repeated ECM injury and resolution. In the work presented here, poly(ethylene glycol)-based hydrogels reversibly stiffen and soften with multiple light stimuli via photoisomerization of an azobenzene-containing cross-linker. Upon irradiation with cytocompatible doses of 365 nm light (10 mW/cm(2), 5 min), isomerization to the azobenzene cis configuration leads to a softening of the hydrogel up to 100-200 Pa (shear storage modulus, G'). This change in gel properties is maintained over a time scale of several hours due to the long half-life of the cis isomer. The initial modulus of the gel can be recovered upon irradiation with similar doses of visible light. With applications in mechanobiology in mind, cytocompatibility with a mechanoresponsive primary cell type is demonstrated. Porcine aortic valvular interstitial cells were encapsulated in the developed hydrogels and shown to exhibit high levels of survival, as well as a spread morphology. The developed hydrogels enable a route to the noninvasive control of substrate modulus independent of changes in the chemical composition or network connectivity, allowing for investigations of the effect of dynamic matrix stiffness on adhered cell behavior.
authors: Howard Hughes Medical Institute and the BioFrontiers Institute and ‡Department of Chemical and Biological Engineering, University of Colorado Boulder , Boulder, Colorado 80303, United States.
authors: Adrianne M
authors: AM
authors: Rosales
authors: Kelly M
authors: KM
authors: Mabry
authors: Eric Michael
authors: EM
authors: Nehls
authors: Kristi S
authors: KS
authors: Anseth
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001391:Azo Compounds / Q000737:chemistry* / Q000494:pharmacology; D001672:Biocompatible Materials / Q000737:chemistry; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004548:Elasticity; D020100:Hydrogels / Q000737:chemistry* / Q000494:pharmacology; D007536:Isomerism; D008422:Materials Testing; D008969:Molecular Sequence Data; D055668:Photochemical Processes; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000494:pharmacology; D034421:Sus scrofa
chemical_list: D001391:Azo Compounds; D001672:Biocompatible Materials; D020100:Hydrogels; D011092:Polyethylene Glycols; C009850:azobenzene
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