具有良好贯通性的颗粒造孔支架的制备及表征

支架孔隙贯通性的研究一直是多孔生物陶瓷的研究重点之一.采用石蜡球作为造孔剂, 在常规的颗粒造孔法制备多孔陶瓷支架的基础上,通过二甲苯处理以便在石蜡球间形成桥联结构, 以扩大颗粒间的接触面积,从而提高多孔陶瓷支架的孔隙贯通性. 借助扫描电镜(SEM)观察陶瓷支架的多孔结构,评价二甲苯处理石蜡球对陶瓷支架孔隙贯通性的改善效果; 采用密度法测定了陶瓷支架的孔隙率并计算其收缩率,并用成骨细胞评价陶瓷支架的细胞相容性. 结果表明,通过二甲苯的处理, 不仅改善了陶瓷支架孔隙的贯通性,而且提高了其孔隙率, 但孔隙率对陶瓷支架的收缩率无明显影响.细胞培养实验显示成骨细胞可进入多孔陶瓷支架内部, 并在材料表面正常生长,贯通性好的多孔陶瓷支架可为成骨细胞生长提供更充分的空间.     

Ceramic Foams with Controlled Geometries Through 3D-Printed Sacrificial Templates

Powder-based 3D printing was combined with sacrificial templating to realize highly porous yttria-stabilized ZrO₂ (YSZ) ceramic foam objects with well-defined geometries. The porous sacrificial template is 3D printed using poly(methyl methacrylate) powder. Various methods are evaluated to optimize ceramic slurry infiltration into the 3D-printed template and subsequent burn-out. The optimized method yields ceramic foam objects with an open porosity of >66% and replicates the geometry of the 3D-printed template with high fidelity.     

不同类型多孔结构生物材料支架制备及其性能优化

多孔支架是组织工程应用中的关键环节,类似细胞外基质的作用,支撑细胞的粘附和随后细胞向组织的衍化。虽然目前已采用多种制备技术研发出大量的多孔支架,但是多孔生物材料支架的制备和性能优化,仍然是组织工程支架领域的研究热点。结合实验室工作,综述了多种制备不同类型多孔结构生物材料支架的制备技术,主要包括颗粒和纤维堆积型支架、泡沫浸渍法支架和颗粒制孔支架等的制备技术,并阐述了这些制备技术对多孔结构支架的孔结构、贯通性和力学性能的改善效果。其目的旨在提供满足组织工程需求的多孔生物材料支架。     

超临界CO2中CS-g-PDLLA的合成及其与PDLLA多孔支架材料的原位构建

首先以辛酸亚锡为催化剂,消旋丙交酯(D,L-LA)与壳聚糖(CS)为原料,在超临界二氧化碳(scCO_2)中合成了以PDLLA为基体、CS-g-PDLLA共聚物为填充相的共混体系,然后通过scCO_2萃取/致孔技术原位构建了CS-g-PDLLA/PDLLA多孔支架材料。对共聚物的结构与性能、PDLLA的分子量进行了表征,对多孔支架的结构形态进行观察,并对支架材料的孔隙率进行测定。结果表明,以scCO_2为反应介质,成功合成了PDLLA均聚物和CS-g-PDLLA共聚物,同时,通过改变原料比、反应温度和时间能在一定程度上调控共聚物的组成与PDLLA的分子量以及产率。CS-g-PDLLA/PDLLA多孔支架材料的孔洞分布均匀,孔洞连通性较好,孔内壁具有非常独特的长沟壑形微观结构,且CS-g-PDLLA填充相与PDLLA基体的相容性良好;减压速率和处理温度对多孔支架的结构形态有一定影响。     

3D打印HA微球支架的制备与表征

生物材料表面微结构对于成骨具有重要的影响,该研究以不同粒径(<60μm)的羟基磷灰石(HA)微球状粉体为原料,通过3D打印技术制备了一系列(HA0、HA10、HA30、HA50)生物陶瓷支架。不同支架具有相似的理化性能,由于微球粒径不同形成了不同的微结构,对其生物学性能造成不同的影响。相比传统非微球颗粒打印的支架(HA0), HA微球构成的支架能够提供更多细胞粘附和生长位点, 24 h的粘附实验显示HA30支架能显著促进骨髓间充质干细胞的伪足伸长;培养5 d的细胞增殖实验显示,微球支架上的细胞数量与HA0支架出现显著性差异,表面微球结构与细胞尺度相当的HA30支架具有最好的促增殖效果。因此,3D打印技术在可控制备HA支架宏观结构的同时,还可以通过控制生物陶瓷粉体的颗粒形貌,调控3D打印支架的表面微结构,从而优化其生物学效应,在骨组织工程领域具有良好的应用前景。     

Micro-CT Analysis of Implanted Poly-Ether-Ether-Ketone Scaffolds: Plasma Immersion Ion Implantation Increases Osteoconduction

Poly-ether-ether-ketone (PEEK) is a biocompatible, high-strength polymer with biomechanical properties similar to soft bone that has been proposed as an alternative to titanium for orthopedic implants. Herein, micro-CT imaging of a 3D printed PEEK scaffold treated with plasma immersion ion implantation (PIII) to assess the degree of osteoconduction relative to an identical untreated structure, by implantation in the scapula of sheep, is performed. To overcome the lack of contrast between soft tissue and PEEK, a customized apparatus and alignment technique is designed and constructed. Principal component analysis is used to accurately locate the boundaries of the implant in the 3D dataset, with respect to reference coordinates. It is found that, within the interior volume of the scaffold, the PIII treated PEEK contains bone that is both more dense and in higher amounts than for untreated PEEK. The untreated PEEK shows more bone immediately outside the boundaries of the scaffold, indicating a lower affinity of the untreated scaffold for in-diffusion of osteocytes and associated mineralization. The greater osteoconduction of the PIII treated scaffold is attributed to the improvement in hydrophilicity and the provision of protein covalent binding.     

三维打印羟基磷灰石晶须增强复合骨修复支架

利用三维打印技术成功制备羟基磷灰石晶须(HAPw)增强的聚己内酯(PCL)复合骨修复支架。通过改变三维打印的挤出速度和挤出气压, 使不同含量HAPw均能在PCL基材中一致排列并均匀分布。PCL支架的机械强度随HAPw含量增加显著提高, 添加33wt%HAPw使PCL支架强度提升了高达3倍。此外, HAPw使PCL支架表面与水的接触角从近100º降低至约50º, 有效改善了细胞表面粘附。经过体外人类骨髓间充质干细胞(hBMSC)在支架上的培养实验, 发现添加HAPw的复合支架具有更好的生物相容性, 能够有效促进hBMSC的增殖生长, 且HAPw-PCL复合支架上细胞具有更高的碱性磷酸酶(ALP)活性和OCN、RUNX2等相关成骨基因表达, 显示出hBMSCs向成骨方向更好的分化及成骨活性。     

Lignin‐Based Direct Ink Printed Structural Scaffolds

3D printing of lignocellulosic biomass (cellulose, hemicellulose, and lignin) has attracted increasing attention by using this abundant, sustainable, and ecofriendly material. While cellulose can be easily tailored into a highly viscous ink for 3D printing, after solvent evaporation, the final printed structures become highly porous, fragile, and easily fall apart in water due to its hydrophilic nature. Lignin, another crucial component of natural lignocellulose, has not yet been reported for ink printing due to its unfavorable rheological behavior. Herein, a low‐cost direct ink printing strategy is developed to fabricate lignin‐based 3D structures with lignin no further refined and a more compact microstructure as well as different functionalities compared with printed cellulose. By using a soft triblock copolymer as the crosslinking agent, the rheology of lignin‐based inks can be adjusted from soft to rigid, and even enables vertical printing which requires stiff and self‐supporting features. The lignin‐based inks contain less water (≈40 wt%) and exhibit a much denser, stiffer structure, resulting in a wet tensile strength of ≈30 MPa, compared to only ≈0.6 MPa for printed cellulose. In addition, the unique macromolecular structure of lignin also demonstrates significantly improved stability in water and under heat, as well as UV‐blocking performance.     

Scalable Fabrication of MXene-PVDF Nanocomposite Triboelectric Fibers via Thermal Drawing

In the data-driven world, textile is a valuable resource for improving the quality of life through continuous monitoring of daily activities and physiological signals of humans. Triboelectric nanogenerators (TENG) are an attractive option for self-powered sensor development by coupling energy harvesting and sensing ability. In this study, to the best of the knowledge, scalable fabrication of Ti₃C₂T_x MXene-embedded polyvinylidene fluoride (PVDF) nanocomposite fiber using a thermal drawing process is presented for the first time. The output open circuit voltage and short circuit current show 53% and 58% improvement, respectively, compared to pristine PVDF fiber. The synergistic interaction between the surface termination groups of MXene and polar PVDF polymer enhances the performance of the fiber. The flexibility of the fiber enables the weaving of fabric TENG devices for large-area applications. The fabric TENG (3 × 2 cm²) demonstrates a power density of 40.8 mW m⁻² at the matching load of 8 MΩ by maintaining a stable performance over 12 000 cycles. Moreover, the fabric TENG has shown the capability of energy harvesting by operating a digital clock and a calculator. A distributed self-powered sensor for human activities and walking pattern monitoring are demonstrated with the fabric.     

100 m Long Thermally Drawn Supercapacitor Fibers with Applications to 3D Printing and Textiles

Supercapacitor fibers, with short charging times, long cycle lifespans, and high power densities, hold promise for powering flexible fabric-based electronics. To date, however, only short lengths of functioning fiber supercapacitors have been produced. The primary goal of this study is to introduce a supercapacitor fiber that addresses the remaining challenges of scalability, flexibility, cladding impermeability, and performance at length. This is achieved through a top-down fabrication method in which a macroscale preform is thermally drawn into a fully functional energy-storage fiber. The preform consists of five components: thermally reversible porous electrode and electrolyte gels; conductive polymer and copper microwire current collectors; and an encapsulating hermetic cladding. This process produces 100 m of continuous functional supercapacitor fiber, orders of magnitude longer than any previously reported. In addition to flexibility (5 mm radius of curvature), moisture resistance (100 washing cycles), and strength (68 MPa), these fibers have an energy density of 306 μWh cm⁻² at 3.0 V and ≈100% capacitance retention over 13 000 cycles at 1.6 V. To demonstrate the utility of this fiber, it is machine-woven and used as filament for 3D printing.     

Gravity Drawing of Micro‐ and Nanofibers for Additive Manufacturing of Well‐Organized 3D‐Nanostructured Scaffolds

This work introduces a gravity fiber drawing (GFD) method of making single filament nanofibers from polymer solutions and precise alignment of the fibers in 3D scaffolds. This method is advantageous for nanofiber 3D alignment in contrast to other known methods. GFD provides a technology for the fabrication of freestanding filament nanofibers of well‐controlled diameter, draw ratio, and 3D organization with controllable spacing and angular orientation between nanofibers. The GFD method is capable of fabricating complex 3D scaffolds combining fibers with different diameters, chemical compositions, mechanical properties, angular orientations, and multilayer structures in the same construct. The scaffold porosity can be as high as 99% to secure transport of nutrients and space for cell infiltration and differentiation in tissue engineering and 3D cell culture applications.     

PLA-PEG共聚物三维多孔支架的制备及表征

将D,L-丙交酯(D,L-LA)与聚乙二醇(PEG)共聚制备了一系列共聚物,并用IR、GPC和1H-NMR对其进行了表征.在此基础上,采用溶剂浇铸-柱子沥滤技术和层叠技术制备了具有一定空间形状的三维多孔组织工程支架,并研究了致孔剂颗粒尺寸及其用量对多孔支架的孔径、孔隙率的影响.结果表明,PLA-PEG共聚物的分子量随着原料中PEG含量的增加而减小;以PLA-PEG共聚物为原料制备多孔支架时,孔径的大小与致孔剂颗粒尺寸有一定的对应关系,孔隙率随着致孔剂用量的增加而增加;采用层叠技术制备的具有一定形状的三维多孔支架符合组织工程对支架材料的一般要求.     

A Simple Modification Method to Obtain Anisotropic and Porous 3D Microfibrillar Scaffolds for Surgical and Biomedical Applications

In native tissues, cellular organization is predominantly anisotropic. Yet, it remains a challenge to engineer anisotropic scaffolds that promote anisotropic cellular organization at macroscopic length scales. To overcome this challenge, an innovative, cheap and easy method to align clinically approved non‐woven surgical microfibrillar scaffolds is presented. The method involves a three‐step process of coating, unidirectional stretching of scaffolds after heating them above glass transition temperature, and cooling back to room temperature. Briefly, a polymer coating is applied to a non‐woven mesh that results in a partial welding of randomly oriented microfibers at their intersection points. The coated scaffold is then heated above the glass transition temperature of the coating and the scaffold polymer. Subsequently, the coated scaffold is stretched to produce aligned and three dimentional (3D) porous fibrillar scaffolds. In a proof of concept study, a polyglycolic acid (PGA) micro‐fibrillar scaffold was coated with poly(4‐hydroxybutirate) (P4HB) acid and subsequently aligned. Fibroblasts were cultured in vitro within the scaffold and results showed an increase in cellular alignment along the direction of the PGA fibers. This method can be scaled up easily for industrial production of polymeric meshes or directly applied to small pieces of scaffolds at the point of care.