29. Jahrestagung der Deutschen Gesellschaft für Biomaterialien

Chair

Prof. Dr.

Professor

Impact of stiffness on biomaterial scaffold tissue engineering following spinal cord injury

Tissue regeneration/regenerated medicine

Implant associated

Abstract text (incl. figure legends and references) Biomaterial engineering using alginate capillary hydrogels (ACHs) is a promising strategy to promote axonal regrowth following spinal cord injury (SCI), given its mechanical tunability, directed growth guidance, and permissive growth substrate. However, due to improper host-scaffold integration and fibroglia scar formation around the ACH, functional axonal regrowth beyond the lesion is marginal. Recent advances in neuronal mechanobiology have renewed interest in optimizing the mechanical properties of biomaterials to match the host tissue and reduce foreign body response to provide seamless integration. So far, the impact of biomaterial mechanics on the injured spinal cord has not been fully investigated. Here, we examine whether stiffness-adjusted ACH scaffolds benefit host integration and axonal growth potential. Following a rat cervical (C5) lateral hemisection SCI, polypeptide-modified ACH scaffolds with an elastic modulus ranging from 10kPa to 1kPa, approaching the stiffness of the adult rat spinal cord, were implanted into the lesion. Four weeks post-implantation, scaffolds with a stiffness approaching that of the spinal cord successfully minimized the host glia, immune, and chondroitin sulfate proteoglycan (CSPG) response around the scaffolds. Simultaneously, the softest scaffold maximized cell infiltration and angiogenesis within capillaries, leading to significant axonal regrowth into the scaffolds. Conversely, the softest scaffold resulted in capillary instability and the least rostral-caudal oriented axonal regrowth. Currently, we are examining the mechanics of implanted ACH scaffolds and the surrounding host tissue via atomic force microscopy. In summary, our findings suggest that stiffness plays a crucial role in scaffold integration with the spinal cord and its effect on axonal regrowth following SCI in vivo. Hence, optimizing the scaffold's mechanical properties could enhance the efficacy of host-scaffold intergration and neuroregenerative properties.

Short Talk

PD Dr.

Design and application of functional gelatin-based biomaterials as drug and cell carriers

Abstract text (incl. figure legends and references) Introduction Gelatin is an attractive starting material in the design of biomaterials due to its inherent degradability, cell adhesion sequences, and hydrogel forming properties that provide environments to cells close to their natural environment, the extracellular matrix. However, gelatin needs to be crosslinked to allow tailoring of properties. Objectives Tailoring and using functional gelatin-based materials. Materials and Methods Aq. solutions of gelatin functionalized with alkynes1 or alkenes2 are crosslinked through alkyne-azide cycloaddition or by photopolymerization. In the former case, crosslinking was performed with variation of small diazide crosslinker type and amount. Hydrogel mechanical properties were tested by rheology, and gelatin chain organization by WAXS, Glycidylmethacrylated gelatins were photocrosslinked in an aqueous two-phase systems in the presence of cells. Cell viability and proliferation, and release of functional proteins were investigated. Results Specific crosslinking with small bifunctional crosslinkers allowed tailoring of mechanical properties and rate of degradation of gelatin-based hydrogels, while unreacted groups were used for attaching dexamethasone via a second click chemistry reaction. Cell encapsulation was achieved without affecting cell viability. Encapsulated L929 and RAMOS Blue cells proliferated and released functional proteins (MMP-9 or secreted embryonic alkaline phosphatase). Conclusion Gelatin crosslinking can be performed in aq. solutions using a variety of organic polymer-analogous reactions. The crosslinking allowed tailoring of material properties and degradation, and enabled access to functional biomaterials e.g. suitable as drug or cell carriers. 1: Eur. Polym. J. 2018, 100, 77-85. 2: Eur. Polym. J. 2021, 142, 110148.

Free-standing collagen fiber scaffolds for soft tissue engineering

Biofabrication

Surface modification technologies

Abstract text (incl. figure legends and references) Introduction: Free-standing scaffolds play a pivotal role in tissue engineering as they promote cell migration due to enhanced nutrient diffusion in comparison to immobilized scaffolds. However, current methods to prepare free-standing scaffolds are often limited to the production of hydrogels, e.g., from fibrin and collagen. Hence, we introduced a new method to assemble collagen into nanofibers that spontaneously detach from the substrate. Methods: Flexible alumina textiles with a tricot knit structure (Zircar Zirconia Inc., USA) were modified with (3-Aminopropyl)triethoxysilane. Collagen nanofibers were assembled on the textiles by adding PBS solution and crosslinked with glutaraldehyde1,2. The morphology of detached collagen was analyzed with scanning electron microscopy, and the mechanical properties were measured by tensile testing. Results: Crosslinked collagen scaffolds spontaneously rolled up with the modified Al2O3 textiles (Fig. 1) and subsequently detached with an inner diameter of 2-4 mm. Mechanical testing of wet collagen scaffolds yielded a mean tensile strength of 3.5 ± 1.9 MPa, 41.0 ± 20.8 MPa for the Young&quot;s modulus and 8.1 ± 3.7% for the elongation at break. Unmodified Al2O3 textiles did not induce any roll-up, as collagen failed to assemble into fibers. Blends of collagen and chitosan formed fibrous composites on silanized Al2O3 textiles, while fibrinogen nanofibers or blends of collagen and elastin did not. These observations suggest that textile porosity and protein charge contribute to scaffold roll-up. Conclusion: We introduced a simple method to prepare free-standing collagen nanofibers on Al2O3 textiles. These self-supporting scaffolds can allow cell cultivation on both sides and could therefore serve, for example, as in vitro models of the basement membrane or skin. References 1 Dutta, D. et al. ACS Appl. Bio Mater. 2021 2 Suter, N. et al. Biofabrication 2021 Fig. 1: Rolled-up Al2O3 textile coated with nanofibrous collagen

Scaffold configuration and micromechanics regulating macrophage-driven biomaterial degradation through mechanosensing

Cell-material interactions

Abstract text (incl. figure legends and references) Question: Biodegradable synthetic scaffolds present a flexible and auspicious category of biomaterials with high application potential in tissue engineering, such as cardiac function restoration.1 The regeneration of functional tissue in situ highly relies on the equilibrium between scaffold degradation and neo-tissue formation. Macrophages play a crucial role in both these processes. This study mainly aimed to investigate the influence of scaffold configuration and micromechanical properties on mechano-sensation and –transduction in macrophages, as well as the degradation behavior of the scaffold driven by macrophages. Methods: Polyesteretherurethane (PEEU), which has been proved to promote angiogenesis2, was prepared either as fiber meshes or as bulk films. The degradation behavior was examined by analyzing morphological and mechanical changes using scanning electron microscopy (SEM), tensile testing, and atomic force microscopy (AFM). The cell recruitment, morphology and reactive oxygen species (ROS) production of macrophages were assessed by SEM, confocal microscopy and ELISA. Results: The promoted oxidative degradation was observed on PEEU mesh with surface elasticity of 1.1 MPa, compared to PEEU film of 187 MPa. As a major trigger of oxidative degradation, ROS was produced to a higher level by macrophages growing on mesh, presenting a 1.5-fold change compared to the film group. Blockage and activation experiment confirmed that ROS secretion and macrophage-driven degradation were mediated by mechano-sensation and –transduction process, including cytoskeleton assembly and Piezo stimulation. Conclusion: The understanding of the mechanosensing process may guide us for future scaffold development. Tung, W. T., et al. Adv Funct Mater 2022, 32 (31). Sun, X. L., et al. Clin Hemorheol Micro 2020, 74 (4), 405-415.

Improving the transendothelial migration behavior of mesoangioblasts in a Boyden-Chamber model to improve the efficiency of a stem cell therapy

Additive manufacturing (e. g. 3D printing)

Abstract text (incl. figure legends and references) Introduction: Mesoangioblasts (MABs), a multipotent muscle tissue stem cell type, have the function to regenerate defective muscle tissue in vivo. It has been shown that this regeneration can also be stimulated by pre-isolated stem cells injected intra-arterially from outside. It is crucial for the efficiency of such a stem cell therapy that as many as possible of the externally added mesoangioblasts reach the site of the diseased tissue. Therefore, it must be investigated what significantly influences the transmembrane migration of this cell type through the endothelial layer of the blood vessel towards the surrounding muscle tissue. While the stimulating effect of the myoblasts has been shown in previous studies, the influence of smooth muscle cells, present in the arterial system, is yet unknown. Objectives: In order to mimic the in vivo conditions, an in vitro model has been developed in our lab within the framework of an EU collaborative project (grant EMR116), which is suitable to study the influence of various factors and thereby gain new insights into how the efficiency of the targeted in vivo stem cell therapy could be increased. Material and Methods: Transwell inserts of a Boyden chamber setup were covered with a monolayer of HUVECs. Smooth muscle cells were seeded in the lower wells at different concentrations and MABs were added to the inserts in suspension. Six hours after seeding, the migrated MABs were fixed and counted. Next to the effect of smooth muscle cells, the presence of the cytokines TNF-alpha and SDF-1 in the medium of the lower compartment was investigated. Results: The migration of MABs through HUVEC monolayers could be successfully stimulated. It was shown that the presence of smooth muscle cells as well as the inflammatory factors TNF-alpha and SDF-1 influence the transendothelial migration of MABs depending on their concentration. Conclusions: The findings could be a clue to improve the efficiency of a stem cell therapy in the future.

Lecture hall 7

Short Talks 6

Tissue Regeneration 1

Short Talk Session

Short Talks 6
Tissue Regeneration 1

Appointment

Chair

Topic

Programme

Short Talks 6Tissue Regeneration 1

Appointment

Chair

Topic

Programme

Short Talks 6
Tissue Regeneration 1