Rapid Diels–Alder Cross-linking of Cell Encapsulating Hydrogels

Abstract

Recent efforts in the design of hydrogel biomaterials have focused on better mimicking the native cellular microenvironment to direct cell fate. To simultaneously control multiple material parameters, several orthogonal chemistries may be needed. However, present strategies to prepare cell-encapsulating hydrogels make use of relatively few chemical reactions. To expand this chemical toolkit, we report the preparation of hydrogels based on a Diels-Alder reaction between fulvenes and maleimides with markedly improved gelation kinetics and hydrolytic stability. Fulvene-maleimide gels cross-link up to 10-times faster than other commonly used DA reaction pairs and remain stable for months under physiological conditions. Furthermore, fulvenemaleimide gels presenting relevant biochemical cues, such as cell-adhesive ligands and proteolytic degradability, support the culture of human mesenchymal stromal cells. Finally, this rapid DA reaction was combined with an orthogonal click reaction to demonstrate how the use of selective chemistries can provide new avenues to incorporate multiple functionalities in hydrogel materials.

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…”

“…[59] For example, Smith et al reported the gelation of furan-terminated hyaluronic acid (HA) upon mixing with bis-maleimide PEG at physiological pH, [60] while Madl and Heilshorn used a fulvenefunctionalized 8-arm PEG crosslinked with an 8-arm maleimidefunctionalized PEG. [61] The inverse-electron demand Diels-Alder (IEDDA) reaction between electron-poor 1,2,4,5-tetrazines and electron-rich dienophiles (e.g., norbornene) is an alternative approach for hydrogel crosslinking. [2] As an example, Alge et al reported that tetrazine-functionalized PEG gelled within minutes of being mixed with a norbornene-functionalized peptidic crosslinker.…”

Biomedical Hydrogels Fabricated Using Diels–Alder Crosslinking

“…Recently the use of fulvene, as diene for DA crosslinking, instead of furan, was proposed to increase the kinetic of hydrogel formation. [ 39 ] Fulvene functionalized 4 arms PEG and fulvene functionalized elastin Like Polypeptide (ELP) were crosslinked with maleimide functionalized 4‐arm‐PEG (star‐PEG‐maleimide). This crosslinking method resulted in strong improvement of gelation kinetic and the gel remained stable for month at physiological condition.…”

Design and Synthesis of Chitosan—Gelatin Hybrid Hydrogels for 3D Printable in vitro Models

“…Chitosan and gelatin were treated with 5-methyl furfural in the presence of NaCNBH 3 to perform a reductive amination, taking advantage of their amino groups, to generate the methyl furan functionalized biopolymers. This reaction has already been investigated on single-chain polymers for the generation of new diagnostic and therapeutic tools for nanomedicine and tissue engineering applications (Hall et al, 2011 ; Nimmo et al, 2011 ; Alge et al, 2013 ; Gandini, 2013 ; Koehler et al, 2013a , b ; Park et al, 2014 ; Gregoritza and Brandl, 2015 ; Stewart et al, 2016 ; Ma et al, 2017 ; Tam et al, 2017 ; Smith et al, 2018 ; Madl and Heilshorn, 2019 ).…”