Synthesis and orthogonal photopatterning of hyaluronic acid hydrogels with thiol-norbornene chemistry.
TL;DR: An orthogonal photopatterning system that utilizes thiol-norbornene chemistry and permits extensive hydrogel modification, including with multiple signals, due to the number of reactive handles accessible for secondary reaction is presented.
About: This article is published in Biomaterials.The article was published on 2013-12-01 and is currently open access. It has received 250 citations till now. The article focuses on the topics: Self-healing hydrogels.
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TL;DR: The techniques that are available for fabricating HMPs, as well as the multiscale behaviours of HMP systems and their functional properties are discussed, highlighting their advantages over traditional bulk hydrogels.
Abstract: Hydrogel microparticles (HMPs) are promising for biomedical applications, ranging from the therapeutic delivery of cells and drugs to the production of scaffolds for tissue repair and bioinks for 3D printing. Biologics (cells and drugs) can be encapsulated into HMPs of predefined shapes and sizes using a variety of fabrication techniques (batch emulsion, microfluidics, lithography, electrohydrodynamic (EHD) spraying and mechanical fragmentation). HMPs can be formulated in suspensions to deliver therapeutics, as aggregates of particles (granular hydrogels) to form microporous scaffolds that promote cell infiltration or embedded within a bulk hydrogel to obtain multiscale behaviours. HMP suspensions and granular hydrogels can be injected for minimally invasive delivery of biologics, and they exhibit modular properties when comprised of mixtures of distinct HMP populations. In this Review, we discuss the fabrication techniques that are available for fabricating HMPs, as well as the multiscale behaviours of HMP systems and their functional properties, highlighting their advantages over traditional bulk hydrogels. Furthermore, we discuss applications of HMPs in the fields of cell delivery, drug delivery, scaffold design and biofabrication.
509 citations
TL;DR: There are now widespread examples of modified HA macromers that form either covalent or physical hydrogels through crosslinking reactions such as with click chemistry or supramolecular assemblies of guest-host pairs.
412 citations
TL;DR: An in situ crosslinking strategy is used for 3D bioprinting of nonviscous photo-crosslinkable hydrogels, allowing fabrication of complex engineered cell-laden constructs.
Abstract: An in situ crosslinking strategy is used for 3D bioprinting of nonviscous photo-crosslinkable hydrogels. This method can be generalized to various photo-crosslinkable formulations, maintaining high embedded cell viability and tunable cell behavior. Heterogeneous and hollow filaments can be printed using this strategy, allowing fabrication of complex engineered cell-laden constructs.
390 citations
TL;DR: This review will focus on the use of photochemical reactions to create dynamic hydrogel environments, and how these dynamic environments are being used to investigate and direct cell behavior.
Abstract: Hydrogels mimic many of the physical properties of soft tissue and are widely used biomaterials for tissue engineering and regenerative medicine. Synthetic hydrogels have been developed to recapitulate many of the healthy and diseased states of native tissues and can be used as a cell scaffold to study the effect of matricellular interactions in vitro. However, these matrices often fail to capture the dynamic and heterogenous nature of the in vivo environment, which varies spatially and during events such as development and disease. To address this deficiency, a variety of manufacturing and processing techniques are being adapted to the biomaterials setting. Among these, photochemistry is particularly well suited because these reactions can be performed in precise three-dimensional space and at specific moments in time. This spatiotemporal control over chemical reactions can also be performed over a range of cell- and tissue-relevant length scales with reactions that proceed efficiently and harmlessly at ambient conditions. This review will focus on the use of photochemical reactions to create dynamic hydrogel environments, and how these dynamic environments are being used to investigate and direct cell behavior.
294 citations
TL;DR: The ability to use light to initiate physicochemical changes in polymers represents one of the most powerful and rapidly evolving approaches as discussed by the authors, which has the unique capacity for enabling 4D manipulation of each of those processes.
264 citations
References
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TL;DR: The radical-mediated thiol-ene reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield.
Abstract: Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chemistry communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, we review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymerizations resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymerization are all reviewed.
3,229 citations
TL;DR: Hydrogels, which consist of highly water swollen cross-linked polymer networks, can now be made with a range of chemistries and a combination of physical and chemical cross-links, finding use in a wide range of applications, including tissue engineering and drug delivery.
Abstract: Hydrogels are polymeric materials distinguished by high water content and diverse physical properties. They can be engineered to resemble the extracellular environment of the body's tissues in ways that enable their use in medical implants, biosensors, and drug-delivery devices. Cell-compatible hydrogels are designed by using a strategy of coordinated control over physical properties and bioactivity to influence specific interactions with cellular systems, including spatial and temporal patterns of biochemical and biomechanical cues known to modulate cell behavior. Important new discoveries in stem cell research, cancer biology, and cellular morphogenesis have been realized with model hydrogel systems premised on these designs. Basic and clinical applications for hydrogels in cell therapy, tissue engineering, and biomedical research continue to drive design improvements using performance-based materials engineering paradigms.
1,552 citations
"Synthesis and orthogonal photopatte..." refers background in this paper
...Hydrogels have become a ubiquitous tool for bioengineers since their properties mimic features of the extracellular environment and can provide structure and molecule delivery to control cell behavior [1,2]....
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TL;DR: A strategy to create photodegradable poly(ethylene glycol)–based hydrogels through rapid polymerization of cytocompatible macromers for remote manipulation of gel properties in situ is reported.
Abstract: We report a strategy to create photodegradable poly(ethylene glycol)-based hydrogels through rapid polymerization of cytocompatible macromers for remote manipulation of gel properties in situ. Postgelation control of the gel properties was 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 was used 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 affect an array of applications from design of drug delivery vehicles to tissue engineering systems.
1,532 citations
"Synthesis and orthogonal photopatte..." refers background in this paper
...For example, light sensitive nitrobenzyl ethermoieties allow for cleavage of chemical groups in gels to reduce gel modulus, introduce topography, or release molecules [6,13,26]....
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TL;DR: The most relevant biopolymer-based hydrogel systems, the different methods of preparation, as well as an in depth overview of the applications in the field of tissue engineering will be given.
1,426 citations
"Synthesis and orthogonal photopatte..." refers background in this paper
...Hydrogels have become a ubiquitous tool for bioengineers since their properties mimic features of the extracellular environment and can provide structure and molecule delivery to control cell behavior [1,2]....
[...]
TL;DR: This review addresses the recent progress in material designs and fabrication approaches leading to the development of bioactive hydrogels as tissue engineering scaffolds as well as exploring different approaches for introducing bioactivity into poly(ethylene glycol) (PEG) hydrogel.
1,132 citations