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- ItemSelf-Hydrophobization in a Dynamic Hydrogel for Creating Nonspecific Repeatable Underwater Adhesion(Weinheim : Wiley-VCH Verlag, 2020) Han, L.; Wang, M.; Prieto-López, L.O.; Deng, X.; Cui, J.Adhesive hydrogels are widely applied for biological and medical purposes; however, they are generally unable to adhere to tissues under wet/underwater conditions. Herein, described is a class of novel dynamic hydrogels that shows repeatable and long-term stable underwater adhesion to various substrates including wet biological tissues. The hydrogels have Fe3+-induced hydrophobic surfaces, which are dynamic and can undergo a self-hydrophobization process to achieve strong underwater adhesion to a diverse range of dried/wet substrates without the need for additional processes or reagents. It is also demonstrated that the hydrogels can directly adhere to biological tissues in the presence of under sweat, blood, or body fluid exposure, and that the adhesion is compatible with in vivo dynamic movements. This study provides a novel strategy for fabricating underwater adhesive hydrogels for many applications, such as soft robots, wearable devices, tissue adhesives, and wound dressings.
- ItemSwitchable double-sided micropatterned adhesives for selective fixation and detachment(Amsterdam : Elsevier, 2019) Tinnemann, V.; Arzt, E.; Hensel, R.Micropatterned dry adhesives are promising candidates for the development of innovative adhesive platforms. Their reversible adhesion to various materials and surfaces has been reported over more than a decade. Switching between a strong and a weak adhesive state can be introduced by elastic buckling instabilities of the microstructure. In this work, we report on novel adhesive pads that exhibit micropatterned pillars on both sides. In double-sided PDMS micropatterns, the dimensions of the pillar structures were tuned by modulating the critical force for buckling during compressive loading. In this way, selective detachment of glass substrates was induced from one side of the pad. Our results indicate a significant switching efficiency of up to 83% between the strong and weak adhesive state. The new structures have high potential for emerging applications where temporary, double-sided fixations in combination with a predetermined detachment location are required. © 2018
- ItemUltra-strong bio-glue from genetically engineered polypeptides([London] : Nature Publishing Group UK, 2021) Ma, Chao; Sun, Jing; Li, Bo; Feng, Yang; Sun, Yao; Xiang, Li; Wu, Baiheng; Xiao, Lingling; Liu, Baimei; Petrovskii, Vladislav S.; Zhang, Jinrui; Wang, Zili; Li, Hongyan; Zhang, Lei; Li, Jingjing; Wang, Fan; Gӧstl, Robert; Potemkin, Igor I.; Chen, Dong; Zeng, Hongbo; Zhang, Hongjie; Liu, Kai; Herrmann, AndreasThe development of biomedical glues is an important, yet challenging task as seemingly mutually exclusive properties need to be combined in one material, i.e. strong adhesion and adaption to remodeling processes in healing tissue. Here, we report a biocompatible and biodegradable protein-based adhesive with high adhesion strengths. The maximum strength reaches 16.5 ± 2.2 MPa on hard substrates, which is comparable to that of commercial cyanoacrylate superglue and higher than other protein-based adhesives by at least one order of magnitude. Moreover, the strong adhesion on soft tissues qualifies the adhesive as biomedical glue outperforming some commercial products. Robust mechanical properties are realized without covalent bond formation during the adhesion process. A complex consisting of cationic supercharged polypeptides and anionic aromatic surfactants with lysine to surfactant molar ratio of 1:0.9 is driven by multiple supramolecular interactions enabling such strong adhesion. We demonstrate the glue’s robust performance in vitro and in vivo for cosmetic and hemostasis applications and accelerated wound healing by comparison to surgical wound closures.
- ItemBicyclic RGD peptides enhance nerve growth in synthetic PEG-based Anisogels(Cambridge : RSC, 2021) Vedaraman, Sitara; Bernhagen, Dominik; Haraszti, Tamas; Licht, Christopher; Castro Nava, Arturo; Omidinia Anarkoli, Abdolrahman; Timmerman, Peter; De Laporte, LauraNerve regeneration scaffolds often consist of soft hydrogels modified with extracellular matrix (ECM) proteins or fragments, as well as linear and cyclic peptides. One of the commonly used integrin-mediated cell adhesive peptide sequences is Arg-Gly-Asp (RGD). Despite its straightforward coupling mechanisms to artificial extracellular matrix (aECM) constructs, linear RGD peptides suffer from low stability towards degradation and lack integrin selectivity. Cyclization of RGD improves the affinity towards integrin subtypes but lacks selectivity. In this study, a new class of short bicyclic peptides with RGD in a cyclic loop and 'random screened' tri-amino acid peptide sequences in the second loop is investigated as a biochemical cue for cell growth inside three-dimensional (3D) synthetic poly(ethylene glycol) (PEG)-based Anisogels. These peptides impart high integrin affinity and selectivity towards either αvβ3 or α5β1 integrin subunits. Enzymatic conjugation of such bicyclic peptides to the PEG backbone enables the formulation of an aECM hydrogel that supports nerve growth. Furthermore, different proteolytic cleavable moieties are incorporated and compared to promote cell migration and proliferation, resulting in enhanced cell growth with different degradable peptide crosslinkers. Mouse fibroblasts and primary nerve cells from embryonic chick dorsal root ganglions (DRGs) show superior growth in bicyclic RGD peptide conjugated gels selective towards αvβ3 or α5β1, compared to monocyclic or linear RGD peptides, with a slight preference to αvβ3 selective bicyclic peptides in the case of nerve growth. Synthetic Anisogels, modified with bicyclic RGD peptides and containing short aligned, magneto-responsive fibers, show oriented DRG outgrowth parallel to the fibers. This report shows the potential of PEG hydrogels coupled with bicyclic RGD peptides as an aECM model and paves the way for a new class of integrin selective biomolecules for cell growth and nerve regeneration.
- ItemSynthetic 3D PEG-Anisogel Tailored with Fibronectin Fragments Induce Aligned Nerve Extension(Columbus, Ohio : American Chemical Society, 2019) Licht, Christopher; Rose, Jonas C.; Anarkoli, Abdolrahman Omidinia; Blondel, Delphine; Roccio, Marta; Haraszti, Tamás; Gehlen, David B.; Hubbell, Jeffrey A.; Lutolf, Matthias P.; De Laporte, LauraAn enzymatically cross-linked polyethylene glycol (PEG)-based hydrogel was engineered to promote and align nerve cells in a three-dimensional manner. To render the injectable, otherwise bioinert, PEG-based material supportive for cell growth, its mechanical and biochemical properties were optimized. A recombinant fibronectin fragment (FNIII9*-10/12-14) was coupled to the PEG backbone during gelation to provide cell adhesive and growth factor binding domains in close vicinity. Compared to full-length fibronectin, FNIII9*-10/12-14 supports nerve growth at similar concentrations. In a 3D environment, only the ultrasoft 1 w/v% PEG hydrogels with a storage modulus of ∼10 Pa promoted neuronal growth. This gel was used to establish the first fully synthetic, injectable Anisogel by the addition of magnetically aligned microelements, such as rod-shaped microgels or short fibers. The Anisogel led to linear neurite extension and represents a large step in the direction of clinical translation with the opportunity to treat acute spinal cord injuries.
- ItemAnalyses and localization of pectin-like carbohydrates in cell wall and mucilage of the green alga Netrium digitus(Wien [u.a.] : Springer, 2010) Eder, M.; Lütz-Meindl, U.The unicellular, simply shaped desmid Netrium digitus inhabiting acid bog ponds grows in two phases. Prior to division, the cell elongates at its central zone, whereas in a second phase, polar tip growth occurs. Electron microscopy demonstrates that Netrium is surrounded by a morphologically homogeneous cell wall, which lacks pores. Immunocytochemical and biochemical analyses give insight into physical wall properties and, thus, into adaptation to the extreme environment. The monoclonal antibodies JIM5 and JIM7 directed against pectic epitopes with different degrees of esterification label preferentially growing wall zones in Netrium. In contrast, 2F4 marks the cell wall only after experimental de-esterification. Electron energy loss spectroscopy reveals Ca-binding capacities of pectins and gives indirect evidence for the degree of their esterification. An antibody raised against Netrium mucilage is not only specific to mucilage but also recognizes wall components in transmission electron microscopy and dot blots. These results indicate a smooth transition between mucilage and the cell wall in Netrium. © 2009 The Author(s).