3D Printed Stem‐Cell Derived Neural Progenitors Generate Spinal Cord Scaffolds

A bioengineered spinal cord is fabricated via extrusion‐based multimaterial 3D bioprinting, in which clusters of induced pluripotent stem cell (iPSC)‐derived spinal neuronal progenitor cells (sNPCs) and oligodendrocyte progenitor cells (OPCs) are placed in precise positions within 3D printed biocompatible scaffolds during assembly. The location of a cluster of cells, of a single type or multiple types, is controlled using a point‐dispensing printing method with a 200 µm center‐to‐center spacing within 150 µm wide channels. The bioprinted sNPCs differentiate and extend axons throughout microscale scaffold channels, and the activity of these neuronal networks is confirmed by physiological spontaneous calcium flux studies. Successful bioprinting of OPCs in combination with sNPCs demonstrates a multicellular neural tissue engineering approach, where the ability to direct the patterning and combination of transplanted neuronal and glial cells can be beneficial in rebuilding functional axonal connections across areas of central nervous system (CNS) tissue damage. This platform can be used to prepare novel biomimetic, hydrogel‐based scaffolds modeling complex CNS tissue architecture in vitro and harnessed to develop new clinical approaches to treat neurological diseases, including spinal cord injury.     

Elastomeric Fibrous Hybrid Scaffold Supports In Vitro and In Vivo Tissue Formation

Biomimetic materials with biomechanical properties resembling those of native tissues while providing an environment for cell growth and tissue formation, are vital for tissue engineering (TE). Mechanical anisotropy is an important property of native cardiovascular tissues and directly influences tissue function. This study reports fabrication of anisotropic cell‐seeded constructs while retaining control over the construct's architecture and distribution of cells. Newly synthesized poly‐4‐hydroxybutyrate (P4HB) is fabricated with a dry spinning technique to create anelastomeric fibrous scaffold that allows control of fiber diameter, porosity, and rate ofdegradation. To allow cell and tissue ingrowth, hybrid scaffolds with mesenchymalstem cells (MSCs) encapsulated in a photocrosslinkable hydrogel were developed. Culturing the cellularized scaffolds in a cyclic stretch/flexure bioreactor resulted in tissue formation and confirmed the scaffold's performance under mechanical stimulation. In vivo experiments showed that the hybrid scaffold is capable of withstanding physiological pressures when implanted as a patch in the pulmonary artery. Aligned tissue formation occurred on the scaffold luminal surface without macroscopic thrombus formation. This combination of a novel, anisotropic fibrous scaffold and a tunable native‐like hydrogel for cellular encapsulation promoted formation of 3D tissue and provides a biologically functional composite scaffold for soft‐tissue engineering applications.     

Electrochemistry assisted reacting deposition of hydroxyapatite in porous chitosan scaffolds

Electrochemistry assisted reacting deposition method was employed to prepare porous chitosan/hydroxyapatite (CS/HA) composite scaffold with a new design device using ion exchange membranes to separate calcium salt and phosphate solutions. The results determined from XRD and SEM indicates hydroxyapatite can be electrochemically deposited in the chitosan scaffold using the device. After electrochemistry assisted reacting deposition, the surface of the chitosan scaffold was coated with low crystalline HA, particularly at the frame edge of the scaffold. The pores in the scaffold still kept interconnected well and the deposited hydroxyapatite has a cluster microsphere shape whose size is about 3-5 μm.     

Fabrication of poly (vinyl alcohol)/ovalbumin/cellulose nanocrystals/nanohydroxyapatite based biocomposite scaffolds

Biocomposite scaffolds composed of PVA, ovalbumin, cellulose nanocrystals, and nanohydroxyapatite were fabricated by freeze-drying method. The results revealed that the different fractions of nanohydroxyapatite and cellulose nanocrystals provide the mechanical strength and stiffness to the desired biocomposite scaffolds. In vitro biomineralization showed the formation of apatite onto the surface of obtained biocomposite scaffolds and increased as amount of nanohydroxyapatite increased. The obtained results suggest that the different combinations of these four biomaterials can be used to fabricate highly porous scaffolds with desired mechanical performance and degradation rate by adjusting ratio for potential use in low load-bearing applications.     

我国附着升降脚手架技术与管理工作的进展

扼要阐述了近年来我国在附着升降脚手架的附着支承方式、架体构造、升降设备、限载同步控制、防坠装置等项技术及其设计与施工安全管理工作的进展情况和尚需继续抓紧解决的问题。     

The Regeneration of Large-Sized and Vascularized Adipose Tissue Using a Tailored Elastic Scaffold and dECM Hydrogels

A dome-shaped elastic poly(l-lactide-co-caprolactone) (PLCL) scaffold with a channel and pore structure was fabricated by a combinative method of 3D printing technology and the gel pressing method (13 mm in diameter and 6.5 mm in thickness) for patient-specific regeneration. The PLCL scaffold was combined with adipose decellularized extracellular matrix (adECM) and heart decellularized extracellular matrix (hdECM) hydrogels and human adipose-derived stem cells (hADSCs) to promote adipogenesis and angiogenesis. These scaffolds had mechanical properties similar to those of native adipose tissue for improved tissue regeneration. The results of the in vitro real-time PCR showed that the dECM hydrogel mixture induces adipogenesis. In addition, the in vivo study at 12 weeks demonstrated that the tissue-engineered PLCL scaffolds containing the hydrogel mixture (hdECM/adECM (80:20)) and hADSCs promoted angiogenesis and adipose tissue formation, and suppressed apoptosis. Therefore, we expect that our constructs will be clinically applicable as material for the regeneration of patient-specific large-sized adipose tissue.     

Three Component Composite Scaffolds Based on PCL,Hydroxyapatite, and L-Lysine Obtained in TIPS-SL: Bioactive Material for Bone Tissue Engineering

In this research, we describe the properties of three-component composite foam scaffolds based on poly(ε-caprolactone) (PCL) as a matrix and hydroxyapatite whiskers (HAP) and L-Lysine as fillers (PCL/HAP/Lys with wt% ratio 50/48/2). The scaffolds were prepared using a thermally induced phase separation technique supported by salt leaching (TIPS-SL). All materials were precisely characterized: porosity, density, water uptake, wettability, DSC, and TGA measurements and compression tests were carried out. The microstructure of the obtained scaffolds was analyzed via SEM. It was found that the PCL/HAP/Lys scaffold has a 45% higher Young’s modulus and better wettability compared to the PCL/HAP system. At the same time, the porosity of the system was ~90%. The osteoblast hFOB 1.19 cell response was also investigated in osteogenic conditions (39 °C) and the cytokine release profile of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α was determined. Modification of PCL scaffolds with HAP and L-Lysine significantly improved the proliferation of pre-osteoblasts cultured on such materials.     

激光选区融化成形多孔硬骨支架的建模、仿真及实验研究

金属3D打印技术成为当前最具有发展潜力和发展前景的工业制造技术之一,通过SLM激光选区烧结技术,选取合理的烧结参数,将金属粉末烧结成型。建立了不同孔径的多孔支架复杂三维模型,并通过有限元分析进行应力、应变的模拟分析,获得了优化后的多孔支架三维模型,为后续的实验研究分析建立理论基础,然后通过SLM烧结技术制备316L不锈钢多孔支架,通过后期热处理实验、压缩试验、金相实验,对多孔试样进行力学性能分析、硬度测试以及表面微观组织分析。通过模拟分析获得优化后的多孔支架孔径尺寸,获得了更适于人体骨骼缺损部位承重的多孔支架,可对后续研究进行指导。实验研究发现300μm孔径支架强度和弹性模量都高于天然骨,而成形多孔结构的金属件保证了骨骼修复体的生物力学性能,具有良好的力学性能。     

Engineering Bioactive M2 Macrophage-Polarized Anti-Inflammatory,Antioxidant, and Antibacterial Scaffolds for Rapid Angiogenesis and Diabetic Wound Repair

Diabetic wound healing still faces great challenges due to the excessive inflammation, easy infection, and impaired angiogenesis in wound beds. The immunoregulation of macrophages polarization toward M2 phenotype that facilitates the transition from inflammation to proliferation phase has been proved to be an effective way to improve diabetic wound healing. Herein, an M2 phenotype-enabled anti-inflammatory, antioxidant, and antibacterial conductive hydrogel scaffolds (GDFE) for producing rapid angiogenesis and diabetic wound repair are reported. The GDFE scaffolds are fabricated facilely through the dynamic crosslinking between polypeptide and polydopamine and graphene oxide. The GDFE scaffolds possess thermosensitivity, self-healing behavior, injectability, broad-spectrum antibacterial activity, antioxidant and anti-inflammatory ability, and electronic conductivity. GDFE effectively activates the polarization of macrophages toward M2 phenotype and significantly promotes the proliferation of dermal fibroblasts, the migration, and in vitro angiogenesis of endothelial cells through paracrine mechanisms. The in vivo results from a full-thickness diabetic wound model demonstrate that GDFE can rapidly promote the diabetic wound repair and skin regeneration, through fast anti-inflammation and angiogenesis and M2 macrophage polarization. This study provides highly efficient strategy for treating diabetic wound repair through designing the M2 polarization-enabled anti-inflammatory, antioxidant, and antibacterial bioactive materials.