Browsing by Subject "Hydrogels"

Now showing 1 - 10 of 21
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    Assessing monocyte phenotype in poly(γ-glutamic acid) hydrogels formed by orthogonal thiol–norbornene chemistry
    (IOP, 2021-07) Kim, Min Hee; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Hydrogels with tunable properties are highly desirable in tissue engineering applications as they can serve as artificial extracellular matrix to control cellular fate processes, including adhesion, migration, differentiation, and other phenotypic changes via matrix induced mechanotransduction. Poly(γ-glutamic acid) (PGA) is an natural anionic polypeptide that has excellent biocompatibility, biodegradability, and water solubility. Moreover, the abundant carboxylic acids on PGA can be readily modified to introduce additional functionality or facilitate chemical crosslinking. PGA and its derivatives have been widely used in tissue engineering applications. However, no prior work has explored orthogonal crosslinking of PGA hydrogels by thiol-norbornene (NB) chemistry. In this study, we report the synthesis and orthogonal crosslinking of PGA-norbornene (PGANB) hydrogels. PGANB was synthesized by standard carbodiimide chemistry and crosslinked into hydrogels via either photopolymerization or enzymatic reaction. Moduli of PGA hydrogels were readily tuned by controlling thiol-NB crosslinking conditions or stoichiometric ratio of functional groups. Orthogonally crosslinked PGA hydrogels were used to evaluate the influence of mechanical cues of hydrogel substrate on the phenotype of naïve human monocytes and M0 macrophages in 3D culture.
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    Click Hydrogels to Assess Stiffness-Induced Activation of Pancreatic Cancer-Associated Fibroblasts and Its Impact on Cancer Cell Spreading
    (Wiley, 2025) Chang, Chun-Yi; Lin, Chien-Chi; Medicine, School of Medicine
    Pancreatic ductal adenocarcinoma (PDAC) is marked by significant desmoplastic reactions, or the accumulation of excessive extracellular matrices. PDAC stroma has abnormally high stiffness, which alters cancer cell behaviors and creates a barrier for effective drug delivery. Unfortunately, clinical trials using a combination of chemotherapy and matrix-degrading enzyme have led to disappointing results, as the degradation of stromal tissue likely accelerated the dissemination of cancer cells. High matrix stiffness has been shown to activate cancer-associated fibroblasts (CAFs), increasing their interaction with pancreatic cancer cells (PCCs) through promoting proliferation, migration, and resistance to chemotherapy. With the advance of biomaterials science and engineering, it is now possible to design chemically defined matrices to understand the role of stiffness in activating pancreatic CAFs and how this may alter cancer cell migration. Here, we developed a norbornene-based click hydrogel system with independently tunable stiffness and cell adhesive ligand to evaluate stiffness-induced activation of CAFs and migration of PCCs. Our results show that matrix stiffness did not alter matrix deposition from CAFs but affected nuclear localization of Yes-associated protein (YAP). Our results also verify the role of CAFs on promoting PCC migration and an elevated substrate stiffness further increased PCC motility.
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    Degradable and Multifunctional PEG-Based Hydrogels Formed by iEDDA Click Chemistry with Stable Click-Induced Supramolecular Interactions
    (American Chemical Society, 2024-02-16) Dimmitt, Nathan H.; Lin, Chien-Chi; Biomedical Engineering, Purdue School of Engineering and Technology
    The inverse electron demand Diels-Alder (iEDDA) reactions are highly efficient click chemistry increasingly utilized in bioconjugation, live cell labeling, and the synthesis and modification of biomaterials. iEDDA click reactions have also been used to cross-link tetrazine (Tz) and norbornene (NB) modified macromers [e.g., multiarm poly(ethylene glycol) or PEG]. In these hydrogels, Tz-NB adducts exhibit stable supramolecular interactions with a high hydrolytic stability. Toward engineering a new class of PEG-based click hydrogels with highly adaptable properties, we previously reported a new group of NB-derivatized PEG macromers via reacting hydroxyl-terminated PEG with carbic anhydride (CA). In this work, we show that c cross-linked by PEGNBCA or its derivatives exhibited fast and tunable hydrolytic degradation. Here, we show that PEGNBCA (either mono- or octafunctional) and its dopamine or tyramine conjugated derivatives (i.e., PEGNB-D and PEGNB-T) readily cross-link with 4-arm PEG-Tz to form a novel class of multifunctional iEDDA click hydrogels. Through modularly adjusting the macromers with unstable and stable iEDDA click-induced supramolecular interactions (iEDDA-CSI), we achieved highly tunable degradation, with full degradation in less than 2 weeks to over two months. We also show that secondary enzymatic reactions could dynamically stiffen these hydrogels. These hydrogels could also be spatiotemporally photopatterned through visible light-initiated photochemistry. Finally, the iEDDA-CSI hydrogels post ester hydrolysis displayed shear-thinning and self-healing properties, enabling injectable delivery.
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    Dual Functionalization of Gelatin for Orthogonal and Dynamic Hydrogel Cross-Linking
    (American Chemical Society, 2021) Kim, Min Hee; Nguyen, Han; Chang, Chun-Yi; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Gelatin based hydrogels are widely used in biomedical fields owing to its abundance of bioactive motifs that support cell adhesion and matrix remodeling. While inherently bioactive, unmodified gelatin exhibits temperature-dependent rheology and solubilizes at body temperature, making it unstable for three-dimensional (3D) cell culture. Therefore, the addition of chemically reactive motifs is required to render gelatin-based hydrogels with highly controllable crosslinking kinetics and tunable mechanical properties that are critical for 3D cell culture. This article provides a series of methods toward establishing orthogonally crosslinked gelatin-based hydrogels for dynamic 3D cell culture. In particular, we prepared dually functionalized gelatin macromers amenable for sequential, orthogonal covalent crosslinking. Central to this material platform is the synthesis of norbornene-functionalized gelatin (GelNB), which forms covalently crosslinked hydrogels via orthogonal thiol-norbornene click crosslinking. Using GelNB as the starting material, we further detail the methods for synthesizing gelatin macromers susceptible to hydroxyphenylacetic acid (HPA) dimerization (i.e., GelNB-HPA) and hydrazone bonding (i.e., GelNB-CH) for on-demand matrix stiffening. Finally, we outline the protocol for synthesizing a gelatin macromer capable of adjusting hydrogel stress-relaxation via boronate ester bonding (i.e., GelNB-BA). The combinations of these orthogonal chemistries affords a wide range of gelatin based hydrogels as biomimetic matrices in tissue engineering and regenerative medicine applications.
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    Enzyme-mediated stiffening hydrogels for probing activation of pancreatic stellate cells
    (Elsevier, 2017-01-15) Liu, Hung-Yi; Greene, Tanja; Lin, Tsai-Yu; Dawes, Camron S.; Korc, Murray; Lin, Chien- Chi; Biomedical Engineering, School of Engineering and Technology
    The complex network of biochemical and biophysical cues in the pancreatic desmoplasia not only presents challenges to the fundamental understanding of tumor progression, but also hinders the development of therapeutic strategies against pancreatic cancer. Residing in the desmoplasia, pancreatic stellate cells (PSCs) are the major stromal cells affecting the growth and metastasis of pancreatic cancer cells by means of paracrine effects and extracellular matrix protein deposition. PSCs remain in a quiescent/dormant state until they are 'activated' by various environmental cues. While the mechanisms of PSC activation are increasingly being described in literature, the influence of matrix stiffness on PSC activation is largely unexplored. To test the hypothesis that matrix stiffness affects myofibroblastic activation of PSCs, we have prepared cell-laden hydrogels capable of being dynamically stiffened through an enzymatic reaction. The stiffening of the microenvironment was created by using a peptide linker with additional tyrosine residues, which were susceptible to tyrosinase-mediated crosslinking. Tyrosinase catalyzes the oxidation of tyrosine into dihydroxyphenylalanine (DOPA), DOPA quinone, and finally into DOPA dimer. The formation of DOPA dimer led to additional crosslinks and thus stiffening the cell-laden hydrogel. In addition to systematically studying the various parameters relevant to the enzymatic reaction and hydrogel stiffening, we also designed experiments to probe the influence of dynamic matrix stiffening on cell fate. Protease-sensitive peptides were used to crosslink hydrogels, whereas integrin-binding ligands (e.g., RGD motif) were immobilized in the network to afford cell-matrix interaction. PSC-laden hydrogels were placed in media containing tyrosinase for 6h to achieve in situ gel stiffening. We found that PSCs encapsulated and cultured in a stiffened matrix expressed higher levels of αSMA and hypoxia-inducible factor 1α (HIF-1α), suggestive of a myofibroblastic phenotype. This hydrogel platform offers a facile means of in situ stiffening of cell-laden matrices and should be valuable for probing cell fate process dictated by dynamic matrix stiffness. STATEMENT OF SIGNIFICANCE: Hydrogels with spatial-temporal controls over crosslinking kinetics (i.e., dynamic hydrogel) are increasingly being developed for studying mechanobiology in 3D. The general principle of designing dynamic hydrogel is to perform cell encapsulation within a hydrogel network that allows for postgelation modification in gel crosslinking density. The enzyme-mediated in situ gel stiffening is innovative because of the specificity and efficiency of enzymatic reaction. Although tyrosinase has been used for hydrogel crosslinking and in situ cell encapsulation, to the best of our knowledge tyrosinase-mediated DOPA formation has not been explored for in situ stiffening of cell-laden hydrogels. Furthermore, the current work provides a gradual matrix stiffening strategy that may more closely mimic the process of tumor development.
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    Heparinized Gelatin-Based Hydrogels for Differentiation of Induced Pluripotent Stem Cells
    (American Chemical Society, 2022) Arkenberg, Matthew R.; Koehler, Karl; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Chemically defined hydrogels are increasingly utilized to define the effects of extracellular matrix (ECM) components on cellular fate determination of human embryonic and induced pluripotent stem cell (hESC and hiPSCs). In particular, hydrogels cross-linked by orthogonal click chemistry, including thiol-norbornene photopolymerization and inverse electron demand Diels-Alder (iEDDA) reactions, are explored for 3D culture of hESC/hiPSCs owing to the specificity, efficiency, cytocompatibility, and modularity of the cross-linking reactions. In this work, we exploited the modularity of thiol-norbornene photopolymerization to create a biomimetic hydrogel platform for 3D culture and differentiation of hiPSCs. A cell-adhesive, protease-labile, and cross-linkable gelatin derivative, gelatin-norbornene (GelNB), was used as the backbone polymer for constructing hiPSC-laden biomimetic hydrogels. GelNB was further heparinized via the iEDDA click reaction using tetrazine-modified heparin (HepTz), creating GelNB-Hep. GelNB or GelNB-Hep was modularly cross-linked with either inert macromer poly(ethylene glycol)-tetra-thiol (PEG4SH) or another bioactive macromer-thiolated hyaluronic acid (THA). The formulations of these hydrogels were modularly tuned to afford biomimetic matrices with similar elastic moduli but varying bioactive components, enabling the understanding of each bioactive component on supporting hiPSC growth and ectodermal, mesodermal, and endodermal fate commitment under identical soluble differentiation cues.
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    Hydrolytically Degradable PEG-Based Inverse Electron Demand Diels-Alder Click Hydrogels
    (American Chemical Society, 2022) Dimmitt, Nathan H.; Arkenberg, Matthew R.; de Lima Perini, Mariana Moraes; Li, Jiliang; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Hydrogels cross-linked by inverse electron demand Diels-Alder (iEDDA) click chemistry are increasingly used in biomedical applications. With a few exceptions in naturally derived and chemically modified macromers, iEDDA click hydrogels exhibit long-term hydrolytic stability, and no synthetic iEDDA click hydrogels can undergo accelerated and tunable hydrolytic degradation. We have previously reported a novel method for synthesizing norbornene (NB)-functionalized multiarm poly(ethylene glycol) (PEG), where carbic anhydride (CA) was used to replace 5-norbornene-2-carboxylic acid. The new PEGNBCA-based thiol-norbornene hydrogels exhibited unexpected fast yet highly tunable hydrolytic degradation. In this contribution, we leveraged the new PEGNBCA macromer for forming iEDDA click hydrogels with [methyl]tetrazine ([m]Tz)-modified macromers, leading to the first group of synthetic iEDDA click hydrogels with highly tunable hydrolytic degradation kinetics. We further exploited Tz and mTz dual conjugation to achieve tunable hydrolytic degradation with an in vitro degradation time ranging from 2 weeks to 3 months. Finally, we demonstrated the excellent in vitro cytocompatibility and in vivo biocompatibility of the new injectable PEGNBCA-based iEDDA click cross-linked hydrogels.
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    Improving Cross-linking of Degradable Thiol-acrylate Hydrogels via Peptide Design
    (Office of the Vice Chancellor for Research, 2015-04-17) Bragg, John C.; Lin, Chien-Chi
    Hydrogels fabricated from poly (ethylene glycol) (PEG) based macromers are ideal for drug delivery and tissue engineering applications. Recently, a new visible light-mediated photopolymerization scheme was developed to fabricate cytocompatible and degradable poly (ethylene glycol)-diacrylate (PEGDA) hydrogels. Co-polymerization of mono-cysteine peptides (e.g. CRGDS) with PEGDA offers the gels with cell adhesion property. However, this approach causes significant reduction in network crosslinking density, in part due to chain transfer of thiols to acrylates. The goal of the project is to improve the network cross-linking efficiency of this peptide-immobilized PEGDA hydrogel for cell culture. We hypothesized that the incorporation of bi-functional bis-cysteine peptides or silk fibroin will produce hydrogels with enhanced stiffness. The shear moduli of the gels were characterized via oscillatory rheometry in strain-sweep (0.1-5%) mode. Hydrolytic degradation of the gels as a function of time was also evaluated by rheometry. Cytocompatibility of the hydrogel system will be assessed by in situ encapsulation of 3T3 fibroblasts. Cell metabolic activity was determined by Alamar-Blue assay. We found that the bis-cysteine peptide enhanced gel crosslinking, as compared with mono-cysteine peptide. Incorporation of silk fibroin protein also exhibited enhancement in gel stiffness. However, the optimum concentration of incorporated silk fibroin presented an increased shear modulus compared to gels containing only the mono-cysteine peptide. Ongoing work is focused on fine-tuning gel formulations and degradation, as well as on evaluating the cytocompatibility of these visible-light cured thiol-acrylate hydrogels.
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    Novel Therapeutics: Can Hydrogels Work to Treat Kidney Disease?
    (Karger, 2023) Soranno, Danielle E.; Rodell, Christopher B.; Pediatrics, School of Medicine
    Background: Hydrogels are water-swollen networks that can be made from a variety of natural and synthetic polymers. Numerous chemistries can be utilized to formulate hydrogels that are injectable, enabling facile in situ delivery of therapeutics such as cytokines or cells. Summary: Cells delivered via injectable hydrogels survive injection better than cells injected in saline or media suspension. Several materials have been used to investigate the use of injectable hydrogels to treat animal models of kidney disease. Species studied to date include mice and rats. This review summarizes the various materials, encapsulated therapeutic payloads, and preclinical models of kidney disease employed to investigate hydrogel injection. Transcutaneous measurements of glomerular filtration rate have demonstrated that delivery of hydrogels under the kidney capsule does not impair kidney function. Key messages: Studies to date have shown the safety and efficacy of hydrogel therapies to treat kidney disease, and numerous studies have demonstrated that hydrogel therapy alone reduces inflammation and fibrosis.