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Unformatted text preview: Photodegradable hydrogels for dynamic tuning of physical and chemical properties April M. Kloxin 1 , Andrea M. Kasko 1,2, , Chelsea N. Salinas 1 , and Kristi S. Anseth 1,2 April M. Kloxin: ; Andrea M. Kasko: ; Chelsea N. Salinas: ; Kristi S. Anseth: Kristi.Anseth@colorado.edu 1 Department of Chemical and Biological Engineering, University of Colorado, 424 UCB ECCH 111, Boulder, CO 80309 USA, Phone: 303.492.7471, Fax: 303.735.0095 2 Howard Hughes Medical Institute, University of Colorado, 424 UCB ECCH 111, Boulder, CO 80309 USA, Phone: 303.492.7471, Fax: 303.735.0095 Abstract We report a strategy to create photodegradable poly(ethylene glycol)-based (PEG) hydrogels through rapid polymerization of cytocompatible macromers for remote manipulation of gel properties in situ. Post-gelation control of the gel properties is demonstrated to introduce temporal changes, creation of arbitrarily shaped features, and on-demand pendant functionality release. Channels photodegraded within a hydrogel containing encapsulated cells allow cell migration. Temporal variation of the biochemical gel composition is utilized to influence chondrogenic differentiation of encapsulated stem cells. Photodegradable gels that allow real-time manipulation of material properties or chemistry provide dynamic environments with the scope to answer fundamental questions about material regulation of live cell function and may impact an array of applications from design of drug delivery vehicles to tissue engineering systems. Hydrogels are hydrophilic polymers swollen by water that are insoluble owing to physical or chemical crosslinks. These water-swollen gels are used extensively as biomaterials for complex device fabrication (1), cell culture for tissue regeneration (2), and targeted drug release (3). Often, sophisticated control of the gel structure in space and time is required to elucidate the dynamic relationship between biomaterial properties and their influence on biological function (4,5). For example, progenitor cells are often expanded and differentiated in hydrogel microenvironments, and researchers have demonstrated how the initial gel properties, including mechanics (6,7) and chemical functionality (8), influence cellular fate. In regenerative medicine, the structure and composition of gels are also regulated temporally, through hydrolytic (9) and enzymatic (10-12) degradation mechanisms, to promote cell secretory properties and encourage the development of tissue-like structures in vitro and in vivo. A major challenge is determining which biochemical and biophysical features must be presented in a gel culture environment. Hydrogel structure and functionality have evolved from the direct encapsulation of cells in simple homogeneous materials to those with highly regulated structures spanning multiple size scales (e.g., through self-assembly (13) or microengineering (14)). These hydrogel structures are further modified locally by cells with the synthetic incorporation of bioresponsive...
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- Spring '08