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- ItemMacroscopic Self-Evolution of Dynamic Hydrogels to Create Hollow Interiors(Weinheim : Wiley-VCH Verlag, 2020) Han, L.; Zheng, Y.; Luo, H.; Feng, J.; Engstler, R.; Xue, L.; Jing, G.; Deng, X.; del Campo, A.; Cui, J.A solid-to-hollow evolution in macroscopic structures is challenging in synthetic materials. A fundamentally new strategy is reported for guiding macroscopic, unidirectional shape evolution of materials without compromising the material's integrity. This strategy is based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. This concept is demonstrated using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling–shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects (for example, spheres, helix tubes, and cubes with different diameters) for different applications.
- ItemThe innate immune response of self-assembling silk fibroin hydrogels(Cambridge : Royal Soc. of Chemistry, 2021) Gorenkova, Natalia; Maitz, Manfred F.; Böhme, Georg; Alhadrami, Hani A.; Jiffri, Essam H.; Totten, John D.; Werner, Carsten; Carswell, Hilary V. O.; Seib, F. PhilippSilk has a long track record of use in humans, and recent advances in silk fibroin processing have opened up new material formats. However, these new formats and their applications have subsequently created a need to ascertain their biocompatibility. Therefore, the present aim was to quantify the haemocompatibility and inflammatory response of silk fibroin hydrogels. This work demonstrated that self-assembled silk fibroin hydrogels, as one of the most clinically relevant new formats, induced very low blood coagulation and platelet activation but elevated the inflammatory response of human whole blood in vitro. In vivo bioluminescence imaging of neutrophils and macrophages showed an acute, but mild, local inflammatory response which was lower than or similar to that induced by polyethylene glycol, a benchmark material. The time-dependent local immune response in vivo was corroborated by histology, immunofluorescence and murine whole blood analyses. Overall, this study confirms that silk fibroin hydrogels induce a similar immune response to that of PEG hydrogels, while also demonstrating the power of non-invasive bioluminescence imaging for monitoring tissue responses. This journal is
- ItemFrom microfluidics to hierarchical hydrogel materials(Amsterdam [u.a.] : Elsevier Science, 2023) Weigel, Niclas; Li, Yue; Fery, Andreas; Thiele, JulianOver the past two decades, microfluidics has made significant contributions to material and life sciences, particularly via the design of nano-, micro- and mesoscale materials such as nanoparticles, micelles, vesicles, emulsion droplets, and microgels. Unmatched in control over a multitude of material parameters, microfluidics has also shed light on fundamental aspects of material design such as the early stages of nucleation and growth processes as well as structure evolution. Exemplarily, polymer hydrogel particles can be formed via microfluidics with exact control over size, shape, functionalization, compartmentalization, and mechanics that is hardly found in any other processing method. Interestingly, the utilization of microfluidics for material design largely focuses on the fabrication of single entities that act as reaction volume for organic and cell-free biosynthesis, cell mimics, or local environment for cell culturing. In recent years, however, hydrogel design has shifted towards structures that integrate a large variety of functions, e.g., to address the demands for sensing tasks in a complex environment or more closely mimicking architecture and organization of tissue by multiparametric cultures. Hence, this review provides an overview of recent literature that explores microfluidics for fabricating hydrogel materials that go well beyond common length scales as well as the structural and functional complexity of microgels necessary to produce hierarchical hydrogel structures. We focus on examples that utilize microfluidics to design microgel-based assemblies, on microfluidically made polymer microgels for 3D bioprinting, on hydrogels fabricated by microfluidics in a continuous fashion, like fibers, and on hydrogel structures that are shaped by microchannels.
- ItemPredicting the orientation of magnetic microgel rods for soft anisotropic biomimetic hydrogels(Cambridge : RSC Publ., 2020) Rose, Jonas C.; Fölster, Maaike; Kivilip, Lukas; Gerardo-Nava, Jose L.; Jaekel, Esther E.; Gehlen, David B.; Rohlfs, Wilko; De Laporte, LauraLiving multicellular organisms comprise a high degree of soft anisotropic tissues but the development of controlled artificial assembly processes to mimic them remains challenging. Therefore, injectable, polymeric, magneto-responsive microgel rods are fabricated to orient within a low magnetic field. The incorporated superparamagnetic nanoparticles induce local dipole moments, resulting in a total magnetic torque that endows microgels with different structural, mechanical, and biochemical properties. In this report, a predictive macroscopic model based on an ellipsoidal element dispersed in a Newtonian fluid is adjusted using experimental data, which enables the prediction of the orientation rate and the required magnetic field strength for various microgel design parameters and fluid viscosities. The ordered microgels are fixed by crosslinking of a surrounding hydrogel, and can be employed for a wide variety of applications where anisotropic composite hydrogels play a crucial role; for instance as adaptive materials or in biomedical applications, wherein the model predictions can reduce animal experiments. © 2019 The Royal Society of Chemistry.
- ItemFractography of poly(: N -isopropylacrylamide) hydrogel networks crosslinked with mechanofluorophores using confocal laser scanning microscopy(Cambridge : RSC Publ., 2020) Stratigaki, Maria; Baumann, Christoph; van Breemen, Lambert C.A.; Heuts, Johan P.A.; Sijbesma, Rint P.; Göstl, RobertDue to their soft and brittle nature, the mechanical characterization of polymer hydrogels is a difficult task employing traditional testing equipment. Here, we endowed poly(N-isopropyl acrylamide) (PNIPAAm) hydrogel networks with Diels-Alder adducts of π-extended anthracenes as mechanofluorophore crosslinkers. After swelling the networks with varying amounts of water and subjecting them to force, we visualized the subsequent fluorescence caused by covalent bond scission with confocal laser scanning microscopy (CLSM) and related the intensities to the macroscopic fracture mechanics and the elastic moduli recorded with traditional uniaxial compression. The sensitivity of the mechanofluorophores allowed the analysis of low levels of mechanical stress produced via a hand-induced needle-puncturing process and, thus, is an alternative to conventional force application methods. The detection and precise localization of covalent bond scission via CLSM helps elucidating the interrelationship between molecular structure and the macroscopic properties of chemically crosslinked polymeric hydrogels. We believe that this micro-scale mechanophore-assisted fractography can establish a new paradigm for the mechanical analysis of soft matter in fields covering traditional polymer and life sciences. © 2019 The Royal Society of Chemistry.
- ItemRedox-triggerable Luciferin-Bioinspired Hydrogels as Injectable and Cell-encapsulating Matrices(Washington, D.C. : American Chemical Society, 2022) Jin, Minye; Gläser, Alisa; Paez, Julieta I.Over the past few decades there has been a great interest in developing smart hydrogels that are stimuli-responsive, due to their ability to respond to variations caused by external stimuli. These materials are exploited for biomedical applications such as biosensors, injectable scaffolds, drug delivery and tissue engineering. Recently, our group reported firefly-inspired hydrogel matrices for 3D cell culture. This platform exhibited certain advantages like rapid gelation rate and tunability of mechanical and biological properties. However, this firstly reported system did not allow for fine control of the gelation onset because the crosslinking reaction started as soon as the two precursors were mixed. Moreover, one of its precursors demonstrated poor storage stability in aqueous solution. These limitations restrict its application as injectable matrices. In this article, we endow the luciferin-inspired hydrogels with redox-triggering capability, to overcome the limitations of the previous system and to widen its application range. We achieve this goal by introducing protected macromers as hydrogel polymeric precursors that can be activated in the presence of a mild reductant, to trigger gel formation in situ with high degree of control. We demonstrate that the regulation of intrinsic (e.g., structure of protecting group, reductant type) and extrinsic (e.g., pH, temperature) parameters of the triggering reaction can be used to modulate key materials properties. This novel upgraded redox-triggerable system enables precise control over gelation onset and kinetics, thus facilitating its utilization as injectable hydrogel without negatively impacting its cytocompatibility. Our findings expand the current toolkit of chemically-based stimuli-responsive hydrogels.
- ItemCytocompatibility Evaluation of PEG-Methylsulfone Hydrogels(Berkeley, CA : University of California, 2023) Trujillo, Sara; Kasper, Jennifer; de Miguel-Jiménez, Adrián; Abt, Britta; Bauer, Alina; Mekontso, Joëlle; Pearson, Samuel; del Campo, AránzazuMethylsulfone derivatized poly(ethylene) glycol (PEG) macromers can be biofunctionalized with thiolated ligands and cross-linked with thiol-based cross-linkers to obtain bioactive PEG hydrogels for in situ cell encapsulation. Methylsulfonyl-thiol (MS-SH) reactions present several advantages for this purpose when compared to other thiol-based cross-linking systems. They proceed with adequate and tunable kinetics for encapsulation, they reach a high conversion degree with good selectivity, and they generate stable reaction products. Our previous work demonstrated the cytocompatibility of cross-linked PEG-MS/thiol hydrogels in contact with fibroblasts. However, the cytocompatibility of the in situ MS-SH cross-linking reaction itself, which generates methylsulfinic acid as byproduct at the cross-linked site, remains to be evaluated. These studies are necessary to evaluate the potential of these systems for in vivo applications. Here we perform an extensive cytocompatibility study of PEG hydrogels during in situ cross-linking by the methylsulfonyl-thiol reaction. We compare these results with maleimide-thiol cross-linked PEGs which are well established for cell culture and in vivo experiments and do not involve the release of a byproduct. We show that fibroblasts and endothelial cells remain viable after in situ polymerization of methylsulfonyl-thiol gels on the top of the cell layers. Cell viability seems better than after in situ cross-linking hydrogels with maleimide-thiol chemistry. The endothelial cell proinflammatory phenotype is low and similar to the one obtained by the maleimide-thiol reaction. Finally, no activation of monocytes is observed. All in all, these results demonstrate that the methylsulfonyl-thiol chemistry is cytocompatible and does not trigger high pro-inflammatory responses in endothelial cells and monocytes. These results make methylsulfonyl-thiol chemistries eligible for in vivo testing and eventually clinical application in the future.