Synthesis of Photocleavable Linear Macromonomers by ATRP and Star Macromonomers by a Tandem ATRP−Click Reaction:  Precursors to Photodegradable Model Networks

Johnson, Jeremiah A.; Finn, M G; Koberstein, Jeffrey T.; Turro, Nicholas J.

doi:10.1021/ma062862b

Cited by 152 publications

(119 citation statements)

References 66 publications

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“…The synthesis of 1,3-dihydroxymethyl-2-nitrobenzene (E) has already been reported in the literature. 22,23 To synthesize 3-hydroxymethyl-2-nitrobenzoic acid, we first oxidize 2-nitrom-xylene using potassium permanganate to obtain 2-nitro-1,3-benzene dicarboxylic acid. We then partially esterify the dicarboxylic acid in refluxing ethanol overnight and isolate 3-(ethoxycarbonyl)-2-nitrobenzoic acid by flash column chromatography.…”

Section: Resultsmentioning

confidence: 99%

Photodegradable Macromers and Hydrogels for Live Cell Encapsulation and Release

Griffin¹,

Kasko²

2012

J. Am. Chem. Soc.

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Hydrogel scaffolds are commonly used as 3D carriers for cells because their properties can be tailored to match natural extra-cellular matrix. Hydrogels may be used in tissue engineering and regenerative medicine to deliver therapeutic cells to injured or diseased tissue through controlled degradation. Hydrolysis and enzymolysis are the two most common mechanisms employed for hydrogel degradation, but neither allows sequential or staged release of cells. In contrast, photodegradation allows external real-time spatial and temporal control over hydrogel degradation, and allows for staged and sequential release of cells. We synthesized and characterized a series of macromers incorporating photodegradbale ortho-nitrobenzyl (o-NB) groups in the macromer backbone. We formed hydrogels from these macromers via redox polymerization and quantified the apparent rate constants of degradation (k app ) of each via photorheology at 370 nm, 10 mW/cm 2 . Decreasing the number of aryl ethers on the o-NB group increases k app , and changing the functionality from primary to seconday at the benzylic site dramatically increases k app . Human mesenchymal stem cells (hMSCs) survive encapsulation in the hydrogels (90% viability post-encapsulation). By exploiting the differences in reactivity of two different o-NB linkers, we quantitatively demonstrate the biased release of one stem cell population (green-fluroescent protein expressing hMSCs) over another (red-fluorescent protein expressing hMSCs).

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Section: Resultsmentioning

confidence: 99%

Photodegradable Macromers and Hydrogels for Live Cell Encapsulation and Release

Griffin¹,

Kasko²

2012

J. Am. Chem. Soc.

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“…The same concept is commonly used to study the structures of macromolecules and control the mechanical properties of synthetic polymer networks (29,32,(35)(36)(37)(38)(39). Consider a general end-linked network comprised of R-A 2 and R′-B f monomers where f represents the network branch functionality.…”

Section: Nds Conceptsmentioning

confidence: 99%

Counting primary loops in polymer gels

Zhou¹,

Woo²,

Cok³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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198

223

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Much of our fundamental knowledge related to polymer networks is built on an assumption of ideal end-linked network structure. Real networks invariably possess topological imperfections that negatively affect mechanical properties; modifications of classical network theories have been developed to account for these defects. Despite decades of effort, there are no known experimental protocols for precise quantification of even the simplest topological network imperfections: primary loops. Here we present a simple conceptual framework that enables primary loop quantification in polymeric materials. We apply this framework to measure the fraction of primary loop junctions in trifunctional PEG-based hydrogels. We anticipate that the concepts described here will open new avenues of theoretical and experimental research related to polymer network structure.responsive materials | topology | network disassembly spectrometry | tetrazine T he properties of all known polymer networks, from commodity materials like nylon, rubber, and plastics, to biological tissues such as the extracellular matrix (ECM) and cartilage, are defined by the network's chemical composition and structural topology (1-3). Much of our fundamental knowledge related to polymer materials, e.g., theories of elasticity and gelation, was built more than half a century ago upon an assumption of ideal end-linked network structure (Fig. 1A) (2, 4-7). Real networks invariably possess imperfections such as first-order elastically inactive dangling chains and primary loops (Fig. 1B), and higher-order elastic loop structures and chain entanglements; modifications of classical network theories have been developed to account for these defects (8-11).First-order network imperfections (Fig. 1B) have the most direct negative impact on the mechanical properties of materials. Dangling chains can be minimized if efficient end-linking reactions are used between functional groups present at 1:1 ratio. In contrast, kinetic constraints demand that primary loops exist regardless of functional group conversion (12). Unlike dangling chains, which can be readily quantified via titration or spectroscopy, there are no known methods for quantification of primary loops. Their prevalence is estimated from pregel measurements or variations between the properties of a given material and theoretical model networks (2,4,(7)(8)(9)(12)(13)(14)(15)(16)(17). These molecular-level mechanical imperfections could critically impact modern applications of polymer networks and gels (18-28), especially those built on an end-linked network architecture (29-33).Here we present a simple conceptual framework called network disassembly spectrometry (NDS) that enables facile, simultaneous quantification of the fraction of primary loops and the numbers and structures of dangling chains in end-linked materials via site-selective network disassembly. We apply this framework to degradable PEG hydrogels, which are similar to materials frequently used in tissue engineering applications (29,32).

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“…The amphiphilic character of the block-copolymers was further demonstrated by surface tension measurements which allowed the critical micellization concentration to be determined. Another recent example of an auto tandem reaction was published by Turro and coworkers [37] combining ATRP and…”

Section: Irmentioning

confidence: 99%

Click Assisted One‐Pot Multi‐Step Reactions in Polymer Science: Accelerated Synthetic Protocols

Lundberg

Hawker

Hult

et al. 2008

Macromol. Rapid Commun.

138

101

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Presently, the majority of reports deal with combining chemical reactions, in a stepwise fashion, to obtain well‐defined polymers. In the future, chemists need to address new challenges such as increase in the range of available efficient reactions, developing libraries of compatible one‐pot reactions, and the application of obtained materials in key industries. Indeed, the rising importance of the click concept has now devised robust synthetic approaches in various fields of research. The unique selectivity of the click reaction is today a new found toolbox for scientists to investigate one‐pot multi‐step systems. Several accelerated protocols have elegantly been reported to obtain a library of advanced polymers.magnified image

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Synthesis of Photocleavable Linear Macromonomers by ATRP and Star Macromonomers by a Tandem ATRP−Click Reaction: Precursors to Photodegradable Model Networks

Cited by 152 publications

References 66 publications

Photodegradable Macromers and Hydrogels for Live Cell Encapsulation and Release

Photodegradable Macromers and Hydrogels for Live Cell Encapsulation and Release

Counting primary loops in polymer gels

Click Assisted One‐Pot Multi‐Step Reactions in Polymer Science: Accelerated Synthetic Protocols

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