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- ItemTime‐Dependent Cation Selectivity of Titanium Carbide MXene in Aqueous Solution(Weinheim : Wiley-VCH, 2022) Wang, Lei; Torkamanzadeh, Mohammad; Majed, Ahmad; Zhang, Yuan; Wang, Qingsong; Breitung, Ben; Feng, Guang; Naguib, Michael; Presser, VolkerElectrochemical ion separation is a promising technology to recover valuable ionic species from water. Pseudocapacitive materials, especially 2D materials, are up-and-coming electrodes for electrochemical ion separation. For implementation, it is essential to understand the interplay of the intrinsic preference of a specific ion (by charge/size), kinetic ion preference (by mobility), and crystal structure changes. Ti3C2Tz MXene is chosen here to investigate its selective behavior toward alkali and alkaline earth cations. Utilizing an online inductively coupled plasma system, it is found that Ti3C2Tz shows a time-dependent selectivity feature. In the early stage of charging (up to about 50 min), K+ is preferred, while ultimately Ca2+ and Mg2+ uptake dominate; this unique phenomenon is related to dehydration energy barriers and the ion exchange effect between divalent and monovalent cations. Given the wide variety of MXenes, this work opens the door to a new avenue where selective ion-separation with MXene can be further engineered and optimized.
- ItemModulating Myeloid Immune Cell Migration Using Multivalently Presented Monosaccharide Ligands for Advanced Immunotherapy(Weinheim : Wiley-VCH Verlag, 2019) Taverno, I.; Rodrigo, A.M.; Kandziora, M.; Kuntz, S.; Dernedde, J.; Trautwein, C.; Tacke, F.; Blas-Garcia, A.; Bartneck, M.Due to their importance for the outcome of the inflammatory response, the motile myeloid cells are a focus of novel treatment options. The interplay of selectins and their ligands with leukocytes and endothelial cells, which mediate endothelial attachment and transmigration of immune cells, can be modulated by selectin‐binding structures. Here, a library of selectin‐targeting ligands coupled to either gold, silver, iron oxide nanospheres, or quantum dots of 5–10 nm in size is used to systematically study their impact on immune cell motility. The multivalent presentation of the carbohydrate mimetics results in very low sub‐nanomolar binding to L ‐selectin. Using human primary monocytes, granulocytes, lymphocytes, and macrophages, it is shown that the ligands exhibit only minor effects on uptake, whereas the motility of leukocytes is critically affected as observed in migration assays evaluated by flow cytometry. The carbohydrate mimetic ring structure, sulfation, in particular, and the degree of ligand presentation, are constituents which cohere in this process. Specific carbohydrate ligands can thus selectively regulate leukocyte subsets. These data form the basis for advanced immunotherapy which inhibits the amplification of inflammation by restricting leukocyte influx to injured tissue sites. Furthermore, the targeting ligands may complement existing treatment options for inflammatory diseases.
- ItemPrintability study of metal ion crosslinked PEG-catechol based inks(Cold Spring Harbor : Cold Spring Harbor Laboratory, 2019) Włodarczyk-Biegun, Malgorzata K.; Paez, Julieta I.; Villiou, Maria; Feng, Jun; del Campo, AranzazuInspired by reversible networks present in nature, we have explored the printability of catechol functionalized polyethylene glycol (PEG) based inks with metal-coordination crosslinking. Material formulations containing Al3+, Fe3+ or V3+ as crosslinking ions were tested. The printability and shape fidelity were dependent on the ink composition (metal ion type, pH, PEG molecular weight) and printing parameters (extrusion pressure and printing speed). The relaxation time, recovery rate and viscosity of the inks were analyzed in rheology studies and correlated with thermodynamic and ligand exchange kinetic constants of the dynamic bonds and the printing performance (i.e. shape fidelity of the printed structures). The relevance of the relaxation time and ligand exchange kinetics for printability was demonstrated. Cells seeded on the crosslinked materials were viable, indicating the potential of the formulations to be used as inks for cell encapsulation. The proposed dynamic ink design offers significant flexibility for 3D (bio)printing, and enables straightforward adjustment of the printable formulation to meet application-specific needs.
- ItemGlycerylphytate as an ionic crosslinker for 3D printing of multi-layered scaffolds with improved shape fidelity and biological features(London : Royal Society of Chemistry, 2020) Mora-Boza, A.; Włodarczyk-Biegun, M.K.; Del Campo, A.; Vázquez-Lasa, B.; Román, J.S.The fabrication of intricate and long-term stable 3D polymeric scaffolds by a 3D printing technique is still a challenge. In the biomedical field, hydrogel materials are very frequently used because of their excellent biocompatibility and biodegradability, however the improvement of their processability and mechanical properties is still required. This paper reports the fabrication of dual crosslinked 3D scaffolds using a low concentrated (<10 wt%) ink of gelatin methacryloyl (GelMA)/chitosan and a novel crosslinking agent, glycerylphytate (G1Phy) to overcome the current limitations in the 3D printing field using hydrogels. The applied methodology consisted of a first ultraviolet light (UV) photopolymerization followed by a post-printing ionic crosslinking treatment with G1Phy. This crosslinker provides a robust framework and avoids the necessity of neutralization with strong bases. The blend ink showed shear-thinning behavior and excellent printability in the form of a straight and homogeneous filament. UV curing was undertaken simultaneously to 3D deposition, which enhanced precision and shape fidelity (resolution ≈150 μm), and prevented the collapse of the subsequent printed layers (up to 28 layers). In the second step, the novel G1Phy ionic crosslinker agent provided swelling and long term stability properties to the 3D scaffolds. The multi-layered printed scaffolds were mechanically stable under physiological conditions for at least one month. Preliminary in vitro assays using L929 fibroblasts showed very promising results in terms of adhesion, spreading, and proliferation in comparison to other phosphate-based traditional crosslinkers (i.e. TPP). We envision that the proposed combination of the blend ink and 3D printing approach can have widespread applications in the regeneration of soft tissues.
- ItemSwitchable Adhesion Surfaces with Enhanced Performance Against Rough Counterfaces(Basel : MDPI, 2016) Prieto-López, Lizbeth; Williams, JohnIn a recent study, we demonstrated that the pressurization of micro-fluidic features introduced in the subsurface of a soft polymer can be used to actively modify the magnitude of the adhesion to a harder counterface by changing its waviness or long wavelength undulations. In that case, both contacting surfaces had very smooth finishes with root-mean-square roughnesses of less than 20 nm. These values are far from those of many engineering surfaces, which usually have a naturally occurring roughness of between ten and a hundred times this value. In this work, we demonstrate that appropriate surface features, specifically relatively slender “fibrils”, can enhance the ability of a such a soft surface to adhere to a hard, but macroscopically rough, counterface, while still maintaining the possibility of switching the adhesion force from one level to another. Conversely, stiffer more conical surface features can suppress adhesion even against a smooth counterface. Examples of each form of topography can be found in the natural world.
- ItemCharacterization of immune cell migration using microfabrication(Berlin ; Heidelberg : Springer, 2021) Vesperini, Doriane; Montalvo, Galia; Qu, Bin; Lautenschläger, FranziskaThe immune system provides our defense against pathogens and aberrant cells, including tumorigenic and infected cells. Motility is one of the fundamental characteristics that enable immune cells to find invading pathogens, control tissue damage, and eliminate primary developing tumors, even in the absence of external treatments. These processes are termed “immune surveillance.” Migration disorders of immune cells are related to autoimmune diseases, chronic inflammation, and tumor evasion. It is therefore essential to characterize immune cell motility in different physiologically and pathologically relevant scenarios to understand the regulatory mechanisms of functionality of immune responses. This review is focused on immune cell migration, to define the underlying mechanisms and the corresponding investigative approaches. We highlight the challenges that immune cells encounter in vivo, and the microfabrication methods to mimic particular aspects of their microenvironment. We discuss the advantages and disadvantages of the proposed tools, and provide information on how to access them. Furthermore, we summarize the directional cues that regulate individual immune cell migration, and discuss the behavior of immune cells in a complex environment composed of multiple directional cues.
- ItemMelt Electrowriting of Scaffolds with a Porosity Gradient to Mimic the Matrix Structure of the Human Trabecular Meshwork(New York : Cold Spring Harbor Laboratory, 2022) Włodarczyk-Biegun, Małgorzata K.; Villiou, Maria; Koch, Marcus; Muth, Christina; Wang, Peixi; Ott, Jenna; del Campo, AranzazuThe permeability of the Human Trabecular Meshwork (HTM) regulates eye pressure via a porosity gradient across its thickness modulated by stacked layers of matrix fibrils and cells. Changes in HTM porosity are associated with increases in intraocular pressure and the progress of diseases like glaucoma. Engineered HTMs could help to understand the structure-function relation in natural tissues, and lead to new regenerative solutions. Here, melt electrowriting (MEW) is explored as a biofabrication technique to produce fibrillar, porous scaffolds that mimic the multilayer, gradient structure of native HTM. Poly(caprolactone) constructs with a height of 125-500 μm and fiber diameters of 10-12 μm are printed. Scaffolds with a tensile modulus between 5.6 and 13 MPa, and a static compression modulus in the range of 6-360 kPa are obtained by varying the scaffolds design, i.e., density and orientation of the fibers and number of stacked layers. Primary HTM cells attach to the scaffolds, proliferate, and form a confluent layer within 8-14 days, depending on the scaffold design. High cell viability and cell morphology close to that in the native tissue are observed. The present work demonstrates the utility of MEW to reconstruct complex morphological features of natural tissues.
- ItemSelf-Adhesive Silicone Microstructures for the Treatment of Tympanic Membrane Perforations(Weinheim : Wiley-VCH, 2021) Lana, Gabriela Moreira; Sorg, Katharina; Wenzel, Gentiana Ioana; Hecker, Dietmar; Hensel, René; Schick, Bernhard; Kruttwig, Klaus; Arzt, EduardInspired by the gecko foot, polymeric microstructures have demonstrated reliable dry adhesion to both stiff objects and sensitive surfaces such as skin. Microstructured silicone patches are proposed, herein, for the treatment of tympanic membrane perforations with the aim of serving as an alternative for current surgical procedures that require anesthesia and ear canal packing. Sylgard 184 PDMS micropillars of 20 μm in diameter and 60 μm in length are topped by a Soft Skin Adhesive (SSA) MG7-1010 terminal layer, of about 25 μm thickness. The adhesion is evaluated by specially designed tack tests against explanted murine eardrums and, for comparison, against a rigid substrate. Functional effects are evaluated using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAE). The adhesion strength of the microstructure and unstructured controls to explanted murine tympanic membranes is comparable (typically 12 kPa), but the microstructured patches are easier to handle by the surgeon. For the first time, partial recovery of hearing performance is measured immediately after patch application. The novel patches adhere without the need for further fixation, removing the need for ear canal packing. The proposed material design holds great promise for improving clinical treatments of tympanic membrane perforations.
- ItemMembrane Tension Orchestrates Rear Retraction in Matrix-Directed Cell Migration(Amsterdam : Elsevier, 2019) Hetmanski, J.H.R.; de, Belly, H.; Busnelli, I.; Waring, T.; Nair, R.V.; Sokleva, V.; Dobre, O.; Cameron, A.; Gauthier, N.; Lamaze, C.; Swift, J.; del, Campo, A.; Starborg, T.; Zech, T.; Goetz, J.G.; Paluch, E.K.; Schwartz, J.-M.; Caswell, P.T.In development, wound healing, and cancer metastasis, vertebrate cells move through 3D interstitial matrix, responding to chemical and physical guidance cues. Protrusion at the cell front has been extensively studied, but the retraction phase of the migration cycle is not well understood. Here, we show that fast-moving cells guided by matrix cues establish positive feedback control of rear retraction by sensing membrane tension. We reveal a mechanism of rear retraction in 3D matrix and durotaxis controlled by caveolae, which form in response to low membrane tension at the cell rear. Caveolae activate RhoA-ROCK1/PKN2 signaling via the RhoA guanidine nucleotide exchange factor (GEF) Ect2 to control local F-actin organization and contractility in this subcellular region and promote translocation of the cell rear. A positive feedback loop between cytoskeletal signaling and membrane tension leads to rapid retraction to complete the migration cycle in fast-moving cells, providing directional memory to drive persistent cell migration in complex matrices. © 2019 The AuthorsCell migration through 3D matrix is critical to developmental and disease processes, but the mechanisms that control rear retraction are poorly understood. Hetmanski et al. show that differential membrane tension allows caveolae to form at the rear of migrating cells and activate the contractile actin cytoskeleton to promote rapid retraction. © 2019 The Authors
- ItemMyxobacteria-Derived Outer Membrane Vesicles: Potential Applicability Against Intracellular Infections(Basel : MDPI, 2020) Goes, Adriely; Lapuhs, Philipp; Kuhn, Thomas; Schulz, Eilien; Richter, Robert; Panter, Fabian; Dahlem, Charlotte; Koch, Marcus; Garcia, Ronald; Kiemer, Alexandra K.; Müller, Rolf; Fuhrmann, GregorIn 2019, it was estimated that 2.5 million people die from lower tract respiratory infections annually. One of the main causes of these infections is Staphylococcus aureus, a bacterium that can invade and survive within mammalian cells. S. aureus intracellular infections are difficult to treat because several classes of antibiotics are unable to permeate through the cell wall and reach the pathogen. This condition increases the need for new therapeutic avenues, able to deliver antibiotics efficiently. In this work, we obtained outer membrane vesicles (OMVs) derived from the myxobacteria Cystobacter velatus strain Cbv34 and Cystobacter ferrugineus strain Cbfe23, that are naturally antimicrobial, to target intracellular infections, and investigated how they can affect the viability of epithelial and macrophage cell lines. We evaluated by cytometric bead array whether they induce the expression of proinflammatory cytokines in blood immune cells. Using confocal laser scanning microscopy and flow cytometry, we also investigated their interaction and uptake into mammalian cells. Finally, we studied the effect of OMVs on planktonic and intracellular S. aureus. We found that while Cbv34 OMVs were not cytotoxic to cells at any concentration tested, Cbfe23 OMVs affected the viability of macrophages, leading to a 50% decrease at a concentration of 125,000 OMVs/cell. We observed only little to moderate stimulation of release of TNF-alpha, IL-8, IL-6 and IL-1beta by both OMVs. Cbfe23 OMVs have better interaction with the cells than Cbv34 OMVs, being taken up faster by them, but both seem to remain mostly on the cell surface after 24 h of incubation. This, however, did not impair their bacteriostatic activity against intracellular S. aureus. In this study, we provide an important basis for implementing OMVs in the treatment of intracellular infections.