Sequential Click Reactions for Synthesizing and Patterning 3D Cell Microenvironments

Department of Chemical and Biological Engineering, University of Colorado, UCB Box 424 Boulder, Colorado 80309-0424, USA.
Nature Material (Impact Factor: 36.5). 07/2009; 8(8):659-64. DOI: 10.1038/nmat2473
Source: PubMed


Click chemistry provides extremely selective and orthogonal reactions that proceed with high efficiency and under a variety of mild conditions, the most common example being the copper(I)-catalysed reaction of azides with alkynes. While the versatility of click reactions has been broadly exploited, a major limitation is the intrinsic toxicity of the synthetic schemes and the inability to translate these approaches into biological applications. This manuscript introduces a robust synthetic strategy where macromolecular precursors react through a copper-free click chemistry, allowing for the direct encapsulation of cells within click hydrogels for the first time. Subsequently, an orthogonal thiol-ene photocoupling chemistry is introduced that enables patterning of biological functionalities within the gel in real time and with micrometre-scale resolution. This material system enables us to tailor independently the biophysical and biochemical properties of the cell culture microenvironments in situ. This synthetic approach uniquely allows for the direct fabrication of biologically functionalized gels with ideal structures that can be photopatterned, and all in the presence of cells.

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Article: Sequential Click Reactions for Synthesizing and Patterning 3D Cell Microenvironments

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    • "Our lab has already utilized click reactions for both microsphere formation and inter-microsphere cross-linking for scaffold stability [44]. Because copper, a common catalyst for these reactions, can be toxic to cells, we have focused on copper-free strain-promoted azide– alkyne cycloadditions, which have high conversions, fast kinetics, insensitivity to oxygen and water, stereospecificity, regiospecificity, and mild reaction conditions [45] [46] [47] [48]. "
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    • "Recently, ''4-D'' hydrogels that enable spatial and temporal patterning of specific ligand geometries in 3-D—the ''fourth dimension'' being time—have been developed in order to guide cellular behaviours such as polarization and migration in real time [124]. For example, Anseth and colleagues exploited the orthogonality between the copper-free azide-alkyne and thiol–ene systems by creating a PEG hydrogel—formed via the former reaction—that could be selectively [125] and reversibly [126] photo-patterned using the latter reaction, post-gelation. In addition to these and other PEG-based hydrogels [127] [128] [129], photo-patterning has also been achieved in ligand-functionalized agarose [130] [131] [132] [133], hyaluronic acid [134] [135] and alginate [136] hydrogels. "
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