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A novel method for fabrication of branched, tubular, perfusable microvessels for use in vascular tissue engineering is reported. A tubular, elastomeric, biodegradable scaffold is first fabricated via a new, double fusible injection molding technique that uses a ternary alloy with a low melting temperature, Field's metal, and paraffin as sacrificial...
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... Common decoupled approaches include fabricating the sacrificial templates via molding, 48,49 droplet-based inkjet bioprinting, 10,50 extrusion bioprinting, 51−58 electrospinning, 59,60 injection molding, 61,62 and selective laser sintering. 42 For these methods, the time the cells spend in hypoxia is determined predominantly by how fast the sacrificial template can be removed (typically minutes), as opposed to how fast it can be fabricated (typically hours for large tissues). ...
Transplantable engineered organs could one day be used to treat patients suffering from end-stage organ failure. Yet, producing hierarchical vascular networks that sustain the viability and function of cells within human-scale organs remains a major challenge. Sacrificial templating has emerged as a promising biofabrication method that could overcome this challenge. Here, we explore and evaluate various strategies and materials that have been used for sacrificial templating. First, we emphasize fabrication approaches that use highly biocompatible sacrificial reagents and minimize the duration that cells spend in fabrication conditions without oxygen and nutrients. We then discuss strategies to create continuous, hierarchical vascular networks, both using biofabrication alone and using hybrid methods that integrate biologically driven vascular self-assembly into sacrificial templating workflows. Finally, we address the importance of structurally reinforcing engineered vessel walls to achieve stable blood flow in vivo, so that engineered organs remain perfused and functional long after implantation. Together, these sacrificial templating strategies have the potential to overcome many current limitations in biofabrication and accelerate clinical translation of transplantable, fully functional engineered organs to rescue patients from organ failure.
... The seeded cells remodeled the matrix over the first week of culture, compacted and created a cylindrical tissue affixed to the polymer wire at each end. As the input cell number increased according to the following groups: 0.05, 0.1, 0.2, 0.3 million cells/tissue by varying the cell seeding density (25,50, 100, 150 million/mL), we observed that more compaction of the hydrogel by cells occurred in the 25 and 50 million/mL groups and less in the 100 and 150 million/mL groups ( Fig. 2A). ...
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In recent years, low‐melting‐point metals including liquid metals, exhibiting outstanding physical and chemical properties such as excellent thermal and electrical conductivity, high surface tension, and biocompatibility, have garnered increasing attention from researchers. The melting point of such metals profoundly influences their properties and determines their range of applications, and comprehending the characteristics and properties of low‐melting‐point metals is crucial for their future applications. Although studies related to liquid metals are growing exponentially in particular, reports exploring the properties and applications of low‐melting‐point metals from the perspective of the melting point are still in their early stages. This review aims to comprehensively summarize the key properties and relevant applications of current low‐melting‐point metals described in recent studies, focusing on gallium‐ and bismuth‐based metal alloys. In addition, this review discusses the opportunities and challenges associated with low‐melting‐point metals, and it is anticipated that this review will contribute to the advancement of low‐melting‐point materials in the fields of flexible electronics and biomedicine, particularly for biomedical applications.
Coronary artery bypass grafting is commonly used to treat cardiovascular diseases by replacing blocked blood vessels with autologous or artificial blood vessels. Nevertheless, the availability of autologous vessels in infants and the elderly and low long-term patency rate of grafts hinder extensive application of autologous vessels in clinical practice. The biological and mechanical properties of the resealable antithrombotic artificial vascular graft (RAAVG) fabricated herein, comprising a bioelectronic conduit based on a tough self-healing polymer (T-SHP) and a lubricious inner coating, match with the functions of autologous blood vessels. The self-healing and elastic properties of the T-SHP confer resistance against mechanical stimuli and promote conformal sealing of suturing regions, thereby preventing leakage (stable fixation under a strain of 50%). The inner layer of the RAAVG presents antibiofouling properties against blood cells and proteins, and antithrombotic properties, owing to its lubricious coating. Moreover, the blood-flow sensor fabricated using the T-SHP and carbon nanotubes is seamlessly integrated into the RAAVG via self-healing and allows highly sensitive monitoring of blood flow at low and high flow rates (10- and 100 mL min-1, respectively). Biocompatibility and feasibility of RAAVG as an artificial graft were demonstrated via ex vivo, and in vivo experiment using a rodent model. The use of RAAVGs to replace blocked blood vessels can improve the long-term patency rate of coronary artery bypass grafts.
Various approaches to reduce the weight of electronics and automobile devices have been explored. For instance, an alternative polymer was utilized to replace metals. In the present study, a new circular braided glass fiber/epoxy composite (braid angle: 45°, fiber: 48 vol%) with a helical structure was fabricated as a model coil spring for weight reduction. A plaster‐sacrificial compression mold was especially designed to fabricate helical composites without voids. The spring design was validated by the experimental results of torsional tests. Plastic deformations of the epoxy resin were measured using creep tests to eliminate high‐temperature plastic deformation (HTPD) of the composites. Pre‐strain applied thermal aging was utilized to remove HTPD. Mechanical properties of the composites were also investigated. The mechanism of mechanical failure was found to be the interfacial failure. For preparation of uncured prepreg, resin permeability was measured to a range of 10⁻¹⁰ m². Resin transfer in the glass fiber‐braided textiles occurred due to the combination of viscous and diffusional flow mechanisms. Based on the results in this study, the facilely designed coil spring composite can be used for various applications, especially automotive parts.
Despite the fact that the field of tissue engineering has had considerable advances over the past two decades, a series of unsolved problems still remain. Vascularization is one of the most important factors that greatly influence the function and size of the engineered scaffolds, which limits the clinical applications. In this work, a facile extracted molding method is presented for fabricating bulk tissue scaffolds with spatial networks. Briefly, the branched templates are designed, coated with paraffin on the surface, immersed into the mixture of microbial transglutaminase and gelatin, and extracted from fully enzymatic cross‐linking gelatin. The perfusion test is done and the mechanical properties of the scaffolds are investigated. Furthermore, in vitro and in vivo experiments demonstrate the nontoxicity and biocompatibility of the materials and fabrication process. Thus, this approach has great potential to overcome the challenge of rapid oxygen and nutrient delivery to engineered vascularized tissues implanted in vivo, opening the way to clinical applications.
Despite considerable advances in tissue engineering over the last two decades, solutions to some crucial problems remain elusive. Vascularization is one of the most important factors that greatly influence the function of scaffolds. Many research studies have focused on the construction of a vascular-like network with pre-vascularization structure. Sacrificial materials are widely used to build perfusable vascular-like architectures, but most of these fabricated scaffolds only have a 2D plane-connected network. The fabrication of three-dimensional perfusable branched networks remains an urgent issue. In this work, we developed a novel sacrificial molding technique for fabricating biocompatible scaffolds with a three-dimensional perfusable branched network. Here, 3D-printed polyvinyl alcohol (PVA) filament was used as the sacrificial material. The fused PVA was deposited on the surface of a cylinder to create the 3D branched solid network. Gelatin was used to embed the solid network. Then, the PVA mold was dissolved after curing the hydrogel. The obtained architecture shows good perfusability. Cell experiment results indicated that human umbilical vein endothelial cells (HUVECs) successfully attached to the surface of the branched channel and maintained high viability after a few days in culture. In order to prevent deformation of the channel, paraffin was coated on the surface of the printed structure, and hydroxyapatite (HA) was added to gelatin. In conclusion, we demonstrate a novel strategy towards the engineering of pre-vasculature thick tissues through the integration of the fused PVA filament deposit. This approach has great potential in solving the issue of three-dimensional perfusable branched networks and opens the way to clinical applications.
