Engineering the 3D structure of organoids.

Organoids form through the sel f-organizing capabilities of stem cells to produce a variety of differentiated cell and tissue types. Most organoid models, however, are limited in terms of the structure and function of the tissues that form, in part because it is difficult to regulate the cell type, arrangement, and cell-cell/cell-matrix interactions within these systems. In this article, we will discuss the engineering approaches to generate more complex organoids with improved function and translational relevance, as well as their advantages and disadvantages.

Bioassembly of hemoglobin-loaded photopolymerizable spheroids alleviates hypoxia-induced cell death.

The delivery of oxygen within tissue engineered constructs is essential for cell survivability; however, achieving this within larger biofabricated constructs poses a significant challenge. Efforts to overcome this limitation often involve the delivery of synthetic oxygen generating compounds. The application of some of these compounds is problematic for the biofabrication of living tissues due to inherent issues such as cytotoxicity, hyperoxia and limited structural stability due to oxygen inhibition of radical-based crosslinking processes.

3D Bioprinting of Collagen-based Microfluidics for Engineering Fully-biologic Tissue Systems.

Microfluidic and organ-on-a-chip devices have improved the physiologic and translational relevance of in vitro systems in applications ranging from disease modeling to drug discovery and pharmacology. However, current manufacturing approaches have limitations in terms of materials used, non-native mechanical properties, patterning of extracellular matrix (ECM) and cells in 3D, and remodeling by cells into more complex tissues. We present a method to 3D bioprint ECM and cells into microfluidic collagen-based high-resolution internally perfusable scaffolds (CHIPS) that address these limitations, expand design complexity, and simplify fabrication.

Primary Glial Cell and Glioblastoma Morphology in Cocultures Depends on Scaffold Design and Hydrogel Composition.

3D cell cultures better replicate the in vivo environment compared to 2D models. Glioblastoma multiforme, a malignant brain tumor, highly profits from its cellular environment. Here, the U87 glioblastoma cell line in the presence/absence of primary astrocytes is studied.

Reinforced Hyaluronic Acid-Based Matrices Promote 3D Neuronal Network Formation.

3D neuronal cultures attempt to better replicate the in vivo environment to study neurological/neurodegenerative diseases compared to 2D models. A challenge to establish 3D neuron culture models is the low elastic modulus (30-500 Pa) of the native brain. Here, an ultra-soft matrix based on thiolated hyaluronic acid (HA-SH) reinforced with a microfiber frame is formulated and used.

Brain and Breast Cancer Cells with PTEN Loss of Function Reveal Enhanced Durotaxis and RHOB Dependent Amoeboid Migration Utilizing 3D Scaffolds and Aligned Microfiber Tracts.

Background: Glioblastoma multiforme (GBM) and metastatic triple-negative breast cancer (TNBC) with mutations often lead to brain dissemination with poor patient outcome, thus new therapeutic targets are needed. To understand signaling, controlling the dynamics and mechanics of brain tumor cell migration, we implemented GBM and TNBC cell lines and designed 3D aligned microfibers and scaffolds mimicking brain structures.

Methods: 3D microfibers and scaffolds were printed using melt electrowriting.

Spinal Cord Neuronal Network Formation in a 3D Printed Reinforced Matrix-A Model System to Study Disease Mechanisms.

3D cell cultures allow a better mimicry of the biological and mechanical environment of cells in vivo compared to 2D cultures. However, 3D cell cultures have been challenging for ultrasoft tissues such as the brain. The present study uses a microfiber reinforcement approach combining mouse primary spinal cord neurons in Matrigel with melt electrowritten (MEW) frames.

Melt Electrospinning of Nanofibers from Medical-Grade Poly(ε-Caprolactone) with a Modified Nozzle.

Melt electrospun fibers, in general, have larger diameters than normally achieved with solution electrospinning. This study uses a modified nozzle to direct-write melt electrospun medical-grade poly(ε-caprolactone) onto a collector resulting in fibers with the smallest average diameter being 275 ± 86 nm under certain processing conditions. Within a flat-tipped nozzle is a small acupuncture needle positioned so that reduces the flow rate to ≈0.

The importance of plasmin for the healing of the anterior cruciate ligament.

Aims: The anterior cruciate ligament (ACL) is known to have a poor wound healing capacity, whereas other ligaments outside of the knee joint capsule such as the medial collateral ligament (MCL) apparently heal more easily. Plasmin has been identified as a major component in the synovial fluid that varies among patients. The aim of this study was to test whether plasmin, a component of synovial fluid, could be a main factor responsible for the poor wound healing capacity of the ACL.

Melt Electrowritten In Vitro Radial Device to Study Cell Growth and Migration.

The development of in vitro assays for 3D microenvironments is essential for understanding cell migration processes. A 3D-printed in vitro competitive radial device is developed to identify preferred Matrigel concentration for glioblastoma migration. Melt electrowriting (MEW) is used to fabricate the structural device with defined and intricate radial structures that are filled with Matrigel.

Cortical Neurons form a Functional Neuronal Network in a 3D Printed Reinforced Matrix.

Impairments in neuronal circuits underly multiple neurodevelopmental and neurodegenerative disorders. 3D cell culture models enhance the complexity of in vitro systems and provide a microenvironment closer to the native situation than with 2D cultures. Such novel model systems will allow the assessment of neuronal network formation and their dysfunction under disease conditions.

3D Electrophysiological Measurements on Cells Embedded within Fiber-Reinforced Matrigel.

2D electrophysiology is often used to determine the electrical properties of neurons. In the brain however, neurons form extensive 3D networks. Thus, performing electrophysiology in a 3D environment provides a closer situation to the physiological condition and serves as a useful tool for various applications in the field of neuroscience.

Development of Bioink from Decellularized Tendon Extracellular Matrix for 3D Bioprinting.

Using decellularized extracellular matrix (dECM) hydrogels as bioinks has been an important step forward for bioprinting of functional tissue constructs, considering their rich microenvironment and their high degree of biomimicry. However, directly using dECM hydrogels as bioinks may not be suitable for bioprinting processes because of the loss of shape fidelity and geometrical precision of bioprinted structure due to their slow gelation kinetics. In this article, the development and direct bioprinting of dECM hydrogel bioink from bovine Achilles tendon were presented.

Genipin-Enhanced Fibrin Hydrogel and Novel Silk for Intervertebral Disc Repair in a Loaded Bovine Organ Culture Model.

(1) Background: Intervertebral disc (IVD) repair represents a major challenge. Using functionalised biomaterials such as silk combined with enforced hydrogels might be a promising approach for disc repair. We aimed to test an IVD repair approach by combining a genipin-enhanced fibrin hydrogel with an engineered silk scaffold under complex load, after inducing an injury in a bovine whole organ IVD culture; (2) Methods: Bovine coccygeal IVDs were isolated from ~1-year-old animals within four hours post-mortem.

Three-dimensional direct cell bioprinting for tissue engineering.

Bioprinting is a relatively new technology where living cells with or without biomaterials are printed layer-by-layer in order to create three-dimensional (3D) living structures. In this article, novel bioprinting methodologies are developed to fabricate 3D biological structures directly from computer models using live multicellular aggregates. Multicellular aggregates made out of at least two cell types from fibroblast, endothelial and smooth muscle cells are prepared and optimized.

Multifunctional 3D printing of heterogeneous hydrogel structures.

Multimaterial additive manufacturing or three-dimensional (3D) printing of hydrogel structures provides the opportunity to engineer geometrically dependent functionalities. However, current fabrication methods are mostly limited to one type of material or only provide one type of functionality. In this paper, we report a novel method of multimaterial deposition of hydrogel structures based on an aspiration-on-demand protocol, in which the constitutive multimaterial segments of extruded filaments were first assembled in liquid state by sequential aspiration of inks into a glass capillary, followed by in situ gel formation.