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    How Much Physical Guidance is Needed to Orient Growing Axons in 3D Hydrogels?
    (Weinheim : Wiley-VCH, 2020) Rose, Jonas C.; Gehlen, David B.; Omidinia-Anarkoli, Abdolrahman; Fölster, Maaike; Haraszti, Tamás; Jaekel, Esther E.; De Laporte, Laura
    Directing cells is essential to organize multi-cellular organisms that are built up from subunits executing specific tasks. This guidance requires a precisely controlled symphony of biochemical, mechanical, and structural signals. While many guiding mechanisms focus on 2D structural patterns or 3D biochemical gradients, injectable material platforms that elucidate how cellular processes are triggered by defined 3D physical guiding cues are still lacking but crucial for the repair of soft tissues. Herein, a recently developed anisotropic injectable hybrid hydrogel (Anisogel) contains rod-shaped microgels that orient in situ by a magnetic field and has propelled studying 3D cell guidance. Here, the Anisogel is used to investigate the dependence of axonal guidance on microgel dimensions, aspect ratio, and distance. While large microgels result in high material anisotropy, they significantly reduce neurite outgrowth and thus the guidance efficiency. Narrow and long microgels enable strong axonal guidance with maximal outgrowth including cell sensing over distances of tens of micrometers in 3D. Moreover, nerve cells decide to orient inside the Anisogel within the first three days, followed by strengthening of the alignment, which goes along with oriented fibronectin deposition. These findings demonstrate the potential of the Anisogel to tune structural and mechanical parameters for specific applications. © 2020 The Authors. Published by Wiley-VCH GmbH
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    Anisometric Microstructures to Determine Minimal Critical Physical Cues Required for Neurite Alignment
    (Weinheim : Wiley-VCH, 2021) Vedaraman, Sitara; Perez-Tirado, Amaury; Haraszti, Tamas; Gerardo-Nava, Jose; Nishiguchi, Akihiro; De Laporte, Laura
    In nerve regeneration, scaffolds play an important role in providing an artificial extracellular matrix with architectural, mechanical, and biochemical cues to bridge the site of injury. Directed nerve growth is a crucial aspect of nerve repair, often introduced by engineered scaffolds imparting linear tracks. The influence of physical cues, determined by well-defined architectures, has been mainly studied for implantable scaffolds and is usually limited to continuous guiding features. In this report, the potential of short anisometric microelements in inducing aligned neurite extension, their dimensions, and the role of vertical and horizontal distances between them, is investigated. This provides crucial information to create efficient injectable 3D materials with discontinuous, in situ magnetically oriented microstructures, like the Anisogel. By designing and fabricating periodic, anisometric, discreet guidance cues in a high-throughput 2D in vitro platform using two-photon lithography techniques, the authors are able to decipher the minimal guidance cues required for directed nerve growth along the major axis of the microelements. These features determine whether axons grow unidirectionally or cross paths via the open spaces between the elements, which is vital for the design of injectable Anisogels for enhanced nerve repair. © 2021 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH