In-situ-forming zwitterionic hydrogel does not ameliorate osteoarthritis in vivo, despite protective effects ex vivo.

Osteoarthritis (OA) is one of the most common degenerative joint diseases, with no effective therapeutic options available. In this study, we aimed to develop an interpenetrating, in-situ-forming hydrogel based on biocompatible and anti-fouling zwitterionic (ZI) polymers for early-stage OA treatment. We hypothesized that the anti-fouling properties of zwitterions could provide tissue protection, and the high charge density of these polymers would enhance tissue penetration and lubrication.

The collagenase-induced osteoarthritis (CIOA) model: Where mechanical damage meets inflammation.

Objective: To characterize inflammatory and mechanical changes in the collagenase-induced OA (CIOA) model in rats.

Design: Skeletally mature, 6-month-old Wistar rats received unilateral intraarticular injections of saline, 500 U or 1000 U of collagenase on days 0 and 2 of the study. Joint tissues were harvested on either day 4 or 70 to evaluate the acute and long-term changes.

Modular iodinated carboxybetaine copolymers as charge-sensitive contrast agents for the detection of cartilage degradation.

Accurately assessing cartilage tissue degradation is a big challenge in osteoarthritis (OA) research, as histology only provides information about a 2D tissue section, and currently available contrast agents for tomographic evaluation suffer from low specificity. In this study, we present a modular platform based on zwitterionic carboxybetaine (CBAA) to create multivalent polymeric contrast agents for x-ray computed tomography (CT) with high specificity towards the anionic glycosaminoglycans in the cartilage tissue. By copolymerizing CBAA with different ratios of anionic and cationic iodinated comonomers, we created a library of polymers with net charges ranging from strongly anionic to strongly cationic.

Foreign Body Immune Response to Zwitterionic and Hyaluronic Acid Granular Hydrogels Made with Mechanical Fragmentation.

Granular hydrogels have recently attracted the attention for diverse tissue engineering applications due to their versatility and modularity. Despite previous studies showing enhanced viability and metabolism of cells encapsulated in these hydrogels, the in vitro immune response and long-term fibrotic response of these scaffolds have not been well characterized. Here, bulk and granular hydrogels are studied based on synthetic zwitterionic (ZI) and natural polysaccharide hyaluronic acid (HA) made with mechanical fragmentation.

Zwitterionic Poly-Carboxybetaine Polymers Restore Lubrication of Inflamed Articular Cartilage.

Osteoarthritis is a degenerative joint disease that is associated with decreased synovial fluid viscosity and increased cartilage friction. Though viscosupplements are available for decades, their clinical efficacy is limited and there is ample need for more effective joint lubricants. This study first evaluates the tribological and biochemical properties of bovine articular cartilage explants after stimulation with the inflammatory cytokine interleukin-1β.

Light from Afield: Fast, High-Resolution, and Layer-Free Deep Vat 3D Printing.

Harnessing light for cross-linking of photoresponsive materials has revolutionized the field of 3D printing. A wide variety of techniques leveraging broad-spectrum light shaping have been introduced as a way to achieve fast and high-resolution printing, with applications ranging from simple prototypes to biomimetic engineered tissues for regenerative medicine. Conventional light-based printing techniques use cross-linking of material in a layer-by-layer fashion to produce complex parts.

Synthetic biodegradable microporous hydrogels for in vitro 3D culture of functional human bone cell networks.

Generating 3D bone cell networks in vitro that mimic the dynamic process during early bone formation remains challenging. Here, we report a synthetic biodegradable microporous hydrogel for efficient formation of 3D networks from human primary cells, analysis of cell-secreted extracellular matrix (ECM) and microfluidic integration. Using polymerization-induced phase separation, we demonstrate dynamic in situ formation of microporosity (5-20 µm) within matrix metalloproteinase-degradable polyethylene glycol hydrogels in the presence of living cells.

Zwitterionic polymer-dexamethasone conjugates penetrate and protect cartilage from inflammation.

Improving the pharmacokinetics of intra-articularly injected therapeutics is a major challenge in treating joint disease. Small molecules and biologics are often cleared from the joint within hours, which greatly reduces their therapeutic efficacy. Furthermore, they are often injected at high doses, which can lead to local cytotoxicity and systemic side effects.

Streamlined, single-step non-viral CRISPR-Cas9 knockout strategy enhances gene editing efficiency in primary human chondrocyte populations.

Background: CRISPR-Cas9-based genome engineering represents a powerful therapeutic tool for cartilage tissue engineering and for understanding molecular pathways driving cartilage diseases. However, primary chondrocytes are difficult to transfect and rapidly dedifferentiate during monolayer (2D) cell culture, making the lengthy expansion of a single-cell-derived edited clonal population not feasible. For this reason, functional genetics studies focused on cartilage and rheumatic diseases have long been carried out in cellular models that poorly recapitulate the native molecular properties of human cartilaginous tissue (e.

Ionically annealed zwitterionic microgels for bioprinting of cartilaginous constructs.

Foreign body response (FBR) is a pervasive problem for biomaterials used in tissue engineering. Zwitterionic hydrogels have emerged as an effective solution to this problem, due to their ultra-low fouling properties, which enable them to effectively inhibit FBR. However, no versatile zwitterionic bioink that allows for high resolution extrusion bioprinting of tissue implants has thus far been reported.

A review of materials used in tomographic volumetric additive manufacturing.

Unlabelled: Volumetric additive manufacturing is a novel fabrication method allowing rapid, freeform, layer-less 3D printing. Analogous to computer tomography (CT), the method projects dynamic light patterns into a rotating vat of photosensitive resin. These light patterns build up a three-dimensional energy dose within the photosensitive resin, solidifying the volume of the desired object within seconds.

FLight Biofabrication Supports Maturation of Articular Cartilage with Anisotropic Properties.

Tissue engineering approaches that recapitulate cartilage biomechanical properties are emerging as promising methods to restore the function of injured or degenerated tissue. However, despite significant progress in this research area, the generation of engineered cartilage constructs akin to native counterparts still represents an unmet challenge. In particular, the inability to accurately reproduce cartilage zonal architecture with different collagen fibril orientations is a significant limitation.

Combining bioengineered human skin with bioprinted cartilage for ear reconstruction.

Microtia is a congenital disorder that manifests as a malformation of the external ear leading to psychosocial problems in affected children. Here, we present a tissue-engineered treatment approach based on a bioprinted autologous auricular cartilage construct (EarCartilage) combined with a bioengineered human pigmented and prevascularized dermo-epidermal skin substitute (EarSkin) tested in immunocompromised rats. We confirmed that human-engineered blood capillaries of EarSkin connected to the recipient's vasculature within 1 week, enabling rapid blood perfusion and epidermal maturation.

Zwitterionic Granular Hydrogel for Cartilage Tissue Engineering.

Zwitterionic hydrogels have high potential for cartilage tissue engineering due to their ultra-hydrophilicity, nonimmunogenicity, and superior antifouling properties. However, their application in this field has been limited so far, due to the lack of injectable zwitterionic hydrogels that allow for encapsulation of cells in a biocompatible manner. Herein, a novel strategy is developed to engineer cartilage employing zwitterionic granular hydrogels that are injectable, self-healing, in situ crosslinkable and allow for direct encapsulation of cells with biocompatibility.

Synergizing Algorithmic Design, Photoclick Chemistry and Multi-Material Volumetric Printing for Accelerating Complex Shape Engineering.

The field of biomedical design and manufacturing has been rapidly evolving, with implants and grafts featuring complex 3D design constraints and materials distributions. By combining a new coding-based design and modeling approach with high-throughput volumetric printing, a new approach is demonstrated to transform the way complex shapes are designed and fabricated for biomedical applications. Here, an algorithmic voxel-based approach is used that can rapidly generate a large design library of porous structures, auxetic meshes and cylinders, or perfusable constructs.

3D Bioprinting in Microgravity: Opportunities, Challenges, and Possible Applications in Space.

3D bioprinting has developed tremendously in the last couple of years and enables the fabrication of simple, as well as complex, tissue models. The international space agencies have recognized the unique opportunities of these technologies for manufacturing cell and tissue models for basic research in space, in particular for investigating the effects of microgravity and cosmic radiation on different types of human tissues. In addition, bioprinting is capable of producing clinically applicable tissue grafts, and its implementation in space therefore can support the autonomous medical treatment options for astronauts in future long term and far-distant space missions.

Shape-defining alginate shells as semi-permeable culture chambers for soft cell-laden hydrogels.

Soft hydrogels have a porous structure that promotes viability and growth of resident cells. However, due to their low structural stability, these materials are fragile and difficult to culture. Here we present a novel approach for the 3D culture of such materials, where a shape-defining, semi-permeable hydrogel shell is used to provide mechanical stability.

Growth factor-loaded sulfated microislands in granular hydrogels promote hMSCs migration and chondrogenic differentiation.

Cell-based therapies for articular cartilage lesions are expensive and time-consuming; clearly, a one-step procedure to induce endogenous repair would have significant clinical benefits. Acellular heterogeneous granular hydrogels were explored for their injectability, cell-friendly cross-linking, and ability to promote migration, as well as to serve as a scaffold for depositing cartilage extracellular matrix. The hydrogels were prepared by mechanical sizing of bulk methacrylated hyaluronic acid (HAMA) and bulk HAMA incorporating sulfated HAMA (SHAMA).

Engineering Inflammation-Resistant Cartilage: Bridging Gene Therapy and Tissue Engineering.

Articular cartilage defects caused by traumatic injury rarely heal spontaneously and predispose into post-traumatic osteoarthritis. In the current autologous cell-based treatments the regenerative process is often hampered by the poor regenerative capacity of adult cells and the inflammatory state of the injured joint. The lack of ideal treatment options for cartilage injuries motivated the authors to tissue engineer a cartilage tissue which would be more resistant to inflammation.

Enzymatically Crosslinked Collagen as a Versatile Matrix for In Vitro and In Vivo Co-Engineering of Blood and Lymphatic Vasculature.

Adequate vascularization is required for the successful translation of many in vitro engineered tissues. This study presents a novel collagen derivative that harbors multiple recognition peptides for orthogonal enzymatic crosslinking based on sortase A (SrtA) and Factor XIII (FXIII). SrtA-mediated crosslinking enables the rapid co-engineering of human blood and lymphatic microcapillaries and mesoscale capillaries in bulk hydrogels.

From Free-Radical to Radical-Free: A Paradigm Shift in Light-Mediated Biofabrication.

In recent years, the development of novel photocrosslinking strategies and photoactivatable materials has stimulated widespread use of light-mediated biofabrication techniques. However, despite great progress toward more efficient and biocompatible photochemical strategies, current photoresins still rely on photoinitiators (PIs) producing radical-initiating species to trigger the so-called free-radical crosslinking/polymerization. In the context of bioprinting, where cells are encapsulated in the bioink, the presence of radicals raises concerns of potential cytotoxicity.

Untethered: using remote magnetic fields for regenerative medicine.

Magnetic fields are increasingly being used for the remote, noncontact manipulation of cells and biomaterials for a wide range of regenerative medical (RM) applications. They have been deployed for their direct effects on biological systems or in conjunction with magnetic materials or magnetically tagged cells for a targeted therapeutic effect. In this work, we highlight the recent trends on the broad use of magnetic fields for the homing of therapeutic cells and particles at targeted tissue sites, biomimetic tissue fabrication, and control of cell fate and proliferation.