29. Jahrestagung der Deutschen Gesellschaft für Biomaterialien

Prof. Dr.

Chair

Tailored hydrogels as a platform technology for various biomedical applications: What is required to create an alginate-based bioink library?

Biofabrication

Additive manufacturing (e. g. 3D printing)

Abstract text (incl. figure legends and references) Introduction: Sodium alginates and their modifications are favorable bioinks for biofabrication strategies due to their biocompatibility and mild gelation. Various printing technologies, like extrusion process and drop-on-demand, have been used to produce complex alginate-based hydrogel structures [1]. Objectives: Establishment of an alginate library for tailored biofabrication applications based on physicochemical analyses, printing accuracy tests and in vitro studies. Materials &amp; methods: Pharmaceutical-grade alginates of different algae sources and their modifications (oxidized to alginate dialdehyde) were used to develop a set of materials consisting of alginate, gelatine and PEGs with a subsequent biomolecular functionalization. These bioinks were investigated regarding their cross-linking degree and physicochemical properties as well as printability and cell behavior. Results: It could be shown that various parameters such as type and source can influence the block structure of alginate which crucially determines the material properties: Alginate-based bioinks with longer G-blocks are characterized by a stronger ionic cross-linking, better printing accuracy and they provide enough stability for cell growth, whereas longer M-blocks degrade faster. However, the M/G ratio had no negative influence on the survival of reporter cells but it affects cell spreading. Conclusion: Molecular weight, M/G ratio, shear thinning properties and printing accuracy, degradation as well as Young&quot;s modulus and biological interaction are required for the use of alginate-based bioinks as a platform technology. We have now been able to bring these together into an &quot;alginate library&quot; through intensive research [2]. Acknowledgments: This project is funded by the Deutsche Forschungs&shy;gemeinschaft (DFG, German Research Foundation) project number 326998133-TRR-225 (subproject B06, A01, B03 and A02). References: [1] J. Hazur, et al., Biofabrication (2020) [2] E. Karakaya, et. al., Biomacromolecules (2023)

Short Talk

Biofabrication with fibers: How to combine 3D bioprinting and programmed fiber spinning

Abstract text (incl. figure legends and references) Biofabrication, a multidisciplinary field that pursues engineering of biologically relevant constructs meant to replicate the complex architecture of human tissues and organs. A promising approach is the use of 3D (bio) printing, which is an advanced biofabrication technique that uses hydrogels to fabricate 3D biological constructs for tissue engineering applications. Hydrogels have shown wide applicability in the fields of tissue engineering and biofabrication as scaffolding materials for decades. Since they are characterized by their high-water retention ability, resembling the extracellular matrix (ECM) of various tissues. However, hydrogels alone do not resemble or mimic the complexity of human tissue ECM, which is composed of fibrous proteins such as collagen and elastin and cell containing ground-like (gel-like) substances such as proteoglycans (PGs) and glycosaminoglycans (GAGs). Wide range of approaches and techniques have been proposed to combine 3D (bio) printing of hydrogels or hydrogel systems with nanofiber fabrication techniques such as electrospinning and melt electrowriting (MEW) for the fabrication of hydrogel-fiber constructs. Each of these fiber-spinning methods possess own drawbacks such as poor control of fiber deposition (electrospinning), slowness (melt electrowriting) and need of use of high voltage and conductive substrates (both electrospinning and melt electrowriting). Herein, a novel biofabrication technique integrating together 3D (bio) printing and fiber spinning based on mechanical pulling to fabricate a multilayered construct of cells encapsulated hydrogel system with highly aligned nanofibers will be presented. In particular, the effect of properties of fiber-forming polymers and rheological properties of bioinks on ability of cells to interact with fiber and move along them will be discussed.

Nano-fibers can improve cell performance, acting as easy-modifiable fillers to upgrade bio-inks.

Cell-material interactions

Abstract text (incl. figure legends and references) Question: In the context of tissue engineering and regenerative medicine, biofabrication can be defined as &quot;'the automated generation of biologically functional products with structural organization from living cells, bioactive molecules, biomaterials, cell aggregates such as micro-tissues, or hybrid cell-material constructs, through bio-printing or bio-assembly and subsequent tissue maturation processes&quot;. Bio-inks are fundamental to high-resolution bio-printing of dimensionally stable scaffolds with sufficient mechanical properties. The development of bio-inks capable of being 3D-printed into cell-containing bio-fabricates is highly demanding. Structural integrity and favorable mechanical properties can be achieved by applying high polymer concentrations in hydrogels. This often comes at the expense of cell performance since cells may become entrapped in the dense matrix. This drawback can be addressed by incorporating fibers as reinforcing fillers that strengthen the overall bio-ink structure and provide a second hierarchical micro-structure. Methods: In this work, we systematically studied the potential impact of collagen-coated short PCL-nano-fibers on cells after being printed in eADF4(C16) bio-inks. We used U-87 MG cells, to investigate the impact of PCL-fiber-reinforcement on cell performance with respect to cell performance studying survival, proliferation and cell morphology up to 7 days in culture. Healthy cells in a cell-friendly environment undergo a change in morphology from a roundish shape, after printing, to an extended, differentiated state. Therefore, individual cells were analysed according to circularity, roundness, solidity and sphericity. Results and Conclusions: In general, we observed that PCL nano-fibers improve cell viability and induced significant morphological changes. Therefore nano-fibers have a positive impact for the overall cell performance in 3D constructs and should be considered as easy-modifiable fillers to upgrade bio-inks.

3D Bioprinting of vasculature based on induced vasculogenesis

Tissue regeneration/regenerated medicine

Abstract text (incl. figure legends and references) Introduction and Aim The in vitro generation of functional vasculature remains a major challenge. Current models use adult cells to mimic the three layers of native blood vessels. Yet, the coordinated morphogenetic events during vasculogenesis are key for vessel functionality and stability. iPSC-derived mesodermal progenitor cells (hiMPCs) remain viable and undergo vasculogenesis after extrusion; still, their patterning into defined shapes is yet to be established. Our study aims to biofabricate complex hierarchical vasculature using hiMPCs. We developed an in-gel bioprinting system to print low-viscosity bioinks into tubular constructs and mimic vasculogenesis. Materials and Methods An alginate-based bioink was supplemented with collagen type I (col I) to promote bioactivity, and xanthan gum (XG) to enhance microporosity. The bioink was extruded into molds and printed into tubular constructs using a XG-based in-gel approach. Cellular viability and morphogenetic capacity over time were evaluated using a viability assay and immunohistochemistry. Results The addition of col I improved cell viability and migration. Differentiation into vascular cell types and formation of vessel-like structures was observed after 2 weeks of culture. The addition of XG resulted in a less dense polymeric network which was hypothesized as beneficial for cell migration. While the alg+col I bioink promoted vasculogenesis and stable formation of vessel structures, the alg+XG+col I bioink promoted the formation of vessels through vacuolization. Conclusion In-gel bioprinting allows the production of shape defined structures using low viscosity bioinks. Stem cells are suitable for the biofabrication of mutilayered wall vascular structures; however, their morphogenetic mechanism depends on the morphology and composition of the matrix. Different matrices are currently under study to further understand these processes.

Biofabrication of a glomerular filtration barrier model through a biomimetic fibrous membrane to mimic functional core components

Abstract text (incl. figure legends and references) The kidney is a highly dynamic organ involved in blood ultrafiltration, hence prone to failure mainly arising from the glomerulus. Filtration occurs through the glomerular filtration barrier (GFB), a tri-layer interface composed of glomerular endothelial cells (GEC), podocytes, and the glomerular basement membrane. Hence, damage to any component of GFB could result in failure of the barrier function, causing proteinuria and kidney disease. This study is aimed at designing a biomimetic artificial basement membrane exploited for the cross-membrane culture of GECs and podocytes and establishing a tri-layer barrier to investigate cell behavior under static and dynamic culture conditions. Firstly, we electrospun nanofibers with random and aligned morphology. Then, the fibers were functionalized with gelatin using polydopamine chemistry to improve cell adhesions. The nanofibers were characterized using SEM, microBCA, and Raman analysis. Thereafter, we established a monolayer of GECs and podocytes on either side of the membranes. Later the membrane was tested under dynamic conditions of flow in a bioreactor. The electrospun mat presents an average thickness of 7 µm, average fiber diameter of 0.6 µm; alignment was present in 86% of the fibers. Porosity of the mat was 43% and 37% for random and aligned. Gelatin release quantified over 21 days was 40 µg/cm2. Cells spread and attached on all tested membranes but indicate an elongated morphology and the formation of a monolayer on the aligned nanofibers. After culturing under flow, filtration is tested in terms of barrier function to albumin. These results confirmed that a surface functionalized artificial GBM can support a co-culture of glomerular cells to model the glomerular functions.

Short Talks 2
TRR225 - Biofabrication

Appointment

Chair

Programme

Short Talks 2TRR225 - Biofabrication

Appointment

Chair

Programme

Short Talks 2
TRR225 - Biofabrication