Nonswelling, Ultralow Content Inverse Electron‐Demand Diels–Alder Hyaluronan Hydrogels with Tunable Gelation Time: Synthesis and In Vitro Evaluation

Abstract

Hyaluronan (HA) is a major component of the extracellular matrix and is particularly attractive for cell‐based assays; yet, common crosslinking strategies of HA hydrogels are not fully tunable and bioorthogonal, and result in gels subject to swelling, which affects their physicochemical properties. To overcome these limitations, HA hydrogels based on the inverse electron‐demand Diels–Alder (IEDDA) “click” reaction are designed. By crosslinking two modified HA components together, as opposed to using telechelic components, tunable gelation times as fast as 4.4 ± 0.4 min and as slow as 46.2 ± 1.8 min are achieved for facile use. By optimizing HA molar mass, ultralow polymer content hydrogels of 0.5% (w/v), resulting in minimal (<3–5% mass variation) to nonswelling (<1%), transparent and biodegradable hydrogels are synthesized. To demonstrate their versatility, the newly designed hydrogels are tested as matrices for 3D cell culture and retinal explant imaging where transparency is important. IEDDA hydrogels are cytocompatible with primary photoreceptors and enable multiphoton imaging of embedded retinal explants for double the time (>38 h) than agarose thermogels (<20 h). IEDDA HA hydrogels constitute a new hydrogel platform. They have low polymer content, tunable gelation time, and are stable, thereby making them suitable for a diversity of applications.

In Situ Forming, Silanized Hyaluronic Acid Hydrogels with Fine Control Over Mechanical Properties and In Vivo Degradation for Tissue Engineering Applications

“…[ 56,57 ] Interestingly, this observation also suggests that Si‐HA gels form relatively permissive environments to cell proliferation, which is a feature rarely observed in covalent systems. [ 13 ] Finally, as cells injected through a needle might experience mortality due to shear stress depending to the flow and viscosity behavior, [ 58 ] we studied if hASCs would remain viable after injection in Si‐HA precursor solutions through a 23G needle (Figure 3F). We showed that cells remain viable (> 85%) in all the conditions, confirming that cells encapsulated in Si‐HA gels are not affected by the injection process.…”

Microfluidic Fabrication of Click Chemistry-Mediated Hyaluronic Acid Microgels: A Bottom-Up Material Guide to Tailor a Microgel’s Physicochemical and Mechanical Properties

“…Based on a previously reported method [ 29 ], the gelation time of HA-hydrogels was estimated by a so-called bulk pipetting test. Briefly, stocks of HA- and PEG-precursor solutions were prepared according to the concentrations as later applied in the fabrication of HA-microgel species ( Table 2 ).…”

Tailoring Gelation Mechanisms for Advanced Hydrogel Applications

“…Michael addition [15,70,71] Thiol-ene addition [16,68,69] Diels-Alder [4 + 2 ] cycloaddition [17,[59][60][61] Inverse-electron demand Diels-Alder cycloaddition [2,[62][63][64][65][66] Disulphide bond formation [18] Hydrazone bond formation [19] -Free-radical polymerization [137][138][139][140][141][142][143] -Polyphenol-based reactions [95][96][97][98][99][100][101] Reactions between polymer chains and nanoparticles -Thiol-ene addition [20,21] -Free-radical polymerization [22] -EDC coupling [23] -Coordinate covalent bond formation [84] Electrostatic interactions Ion-polymer interactions [24][25][26][27][28][29] Polymer-polymer interactions [31,32] Other noncovalent interactions Polymer-polymer interactions [33,…”

“…Noncovalent interactions between complementary groups -Mixing-induced two-component hydrogels [53] -DNA-PNA methacrylamide hydrogels [72] -DNA-polypeptide hydrogels [73] -Enantiomer-functionalized dextran hydrogels [74] -Host-guest cyclodextrin hydrogels [76] -Cucurbit[n]uril hydrogels [77] Covalent crosslinking -Gelatin-based hydrogels [11,55,63] -Collagen-based hydrogels [54] -Fibrinogen-based hydrogels [56] -Chitosan-based hydrogels [57] -Alginate-based hydrogels [64] -HA-based hydrogels [65,66] -PEG-based hydrogels [58,[60][61][62]66,67,[69][70][71] Nanoparticle-based -Methylcellulose-based hydrogels [78,79] -HA-based hydrogels [79,82] -PEG-based hydrogels [80,81,84] -DNA-based hydrogels [83] Change in pH…”

“…reported that tetrazine‐functionalized PEG gelled within minutes of being mixed with a norbornene‐functionalized peptidic crosslinker. [ 62 ] This crosslinking strategy has also been demonstrated for the formation of gelatin, [ 63 ] alginate, [ 64 ] HA, [ 65 ] and HA‐PEG hydrogels. [ 66 ] A less commonly explored reaction is the Huisgen 1,3‐cycloaddition between hydroximoyl chloride and norbornene.…”