3D polylactide-based scaffolds for studying human hepatocarcinoma processes in vitro

We evaluated the combination of leaching techniques and melt blending of polymers and particles for the preparation of highly interconnected three-dimensional polymeric porous scaffolds for in vitro studies of human hepatocarcinoma processes. More specifically, sodium chloride and poly(ethylene glycol) (PEG) were used as water-soluble porogens to form porous and solvent-free poly(L,D-lactide) (PLA)-based scaffolds. Several characterization techniques, including porosimetry, image analysis and thermogravimetry, were combined to improve the reliability of measurements and mapping of the size, distribution and microarchitecture of pores. We also investigated the effect of processing, in PLA-based blends, on the simultaneous bulk/surface modifications and pore architectures in the scaffolds, and assessed the effects on human hepatocarcinoma viability and cell adhesion. The influence of PEG molecular weight on the scaffold morphology and cell viability and adhesion were also investigated. Morphological studies indicated that it was possible to obtain scaffolds with well-interconnected pores of assorted sizes. The analysis confirmed that SK-Hep1 cells adhered well to the polymeric support and emitted surface protrusions necessary to grow and differentiate three-dimensional systems. PEGs with higher molecular weight showed the best results in terms of cell adhesion and viability.     

新型生物降解交联剂的制备及其在壳聚糖交联膜中的应用

本文用聚乙二醇和丙交酯在辛酸亚锡的催化作用下合成了可降解的二羟基中间体,再与2,4-甲苯二异氰酸酯(2,4-TDI)反应,合成了异氰酸酯基封端的一系列生物降解型交联剂.并且对中间体和交联剂进行了 FTIR分析表征.应用交联剂对壳聚糖膜材料进行交联,并对交联材料进行了吸水率,表面接触角及力学性能的测定,结果表明新型生物降解交联剂的运用不仪改善了材料吸水性,也提高了材料的力学性能.     

Shining Light on Poly(ethylene glycol): From Polymer Modification to 3D Laser Printing of Water Erasable Microstructures

The implementation of stimuli-responsive bonds into 3D network assemblies is a key concept to design adaptive materials that can reshape and degrade. Here, a straightforward but unique photoresist is introduced for the tailored fabrication of poly(ethylene glycol) (PEG) materials that can be readily erased by water, even without the need for acidic or basic additives. Specifically, a new class of photoresist is developed that operates through the backbone crosslinking of PEG when irradiated in the presence of a bivalent triazolinedione. Hence, macroscopic gels are obtained upon visible light-emitting diode irradiation (λ > 515 nm) that are stable in organic media but rapidly degrade upon the addition of water. Photoinduced curing is also applicable to multiphoton laser lithography (λ > 700 nm), hence providing access to 3D printed microstructures that vanish when immersed in water at 37 °C. Materials with varying crosslinking densities are accessed by adapting the applied laser writing power, thereby allowing for tunable hydrolytic erasing timescales. A new platform technology is thus presented that enables the crosslinking and 3D laser printing of PEG-based materials, which can be cleaved and erased in water, and additionally holds potential for the facile modification and backbone degradation of polyether-containing materials in general.     

Evaluation of synovium-derived mesenchymal stem cells and 3D printed nanocomposite scaffolds for tissue engineering

Stem cells and scaffolds play a very important role in tissue engineering. Here, we isolated synovium-derived mesenchymal stem cells (SMSCs) from synovial membrane tissue and characterized stem-cell properties. Gelatin nanoparticles (NP) were prepared using a two-step desolvation method and then pre-mixed into different host matrix (silk fibroin (SF), gelatin (Gel), or SF–Gel mixture) to generate various 3D printed nanocomposite scaffolds (NP/SF, NP/SF–Gel, NP/Gel-1, and NP/Gel-2). The microstructure was examined by scanning electron microscopy. Biocompatibility assessment was performed through CCK-8 assay by coculturing with SMSCs at 1, 3, 7 and 14 days. According to the results, SMSCs are similar to other MSCs in their surface epitope expression, which are negative for CD45 and positive for CD44, CD90, and CD105. After incubation in lineage-specific medium, SMSCs could differentiate into chondrocytes, osteocytes and adipocytes. 3D printed nanocomposite scaffolds exhibited a good biocompatibility in the process of coculturing with SMSCs and had no negative effect on cell behavior. The study provides a strategy to obtain SMSCs and fabricate 3D printed nanocomposite scaffolds, the combination of which could be used for practical applications in tissue engineering.     

Evaluation of synovium-derived mesenchymal stem cells and 3D printed nanocomposite scaffolds for tissue engineering

Abstract

Stem cells and scaffolds play a very important role in tissue engineering. Here, we isolated synovium-derived mesenchymal stem cells (SMSCs) from synovial membrane tissue and characterized stem-cell properties. Gelatin nanoparticles (NP) were prepared using a two-step desolvation method and then pre-mixed into different host matrix (silk fibroin (SF), gelatin (Gel), or SF–Gel mixture) to generate various 3D printed nanocomposite scaffolds (NP/SF, NP/SF–Gel, NP/Gel-1, and NP/Gel-2). The microstructure was examined by scanning electron microscopy. Biocompatibility assessment was performed through CCK-8 assay by coculturing with SMSCs at 1, 3, 7 and 14 days. According to the results, SMSCs are similar to other MSCs in their surface epitope expression, which are negative for CD45 and positive for CD44, CD90, and CD105. After incubation in lineage-specific medium, SMSCs could differentiate into chondrocytes, osteocytes and adipocytes. 3D printed nanocomposite scaffolds exhibited a good biocompatibility in the process of coculturing with SMSCs and had no negative effect on cell behavior. The study provides a strategy to obtain SMSCs and fabricate 3D printed nanocomposite scaffolds, the combination of which could be used for practical applications in tissue engineering.     

壳聚糖/聚己内酯-聚乳酸多孔支架制备和表征

为调控骨组织工程支架的力学性能和降解性能,采用相分离方法,以冰醋酸-水为共溶剂配制聚合物溶液,以NaOH溶液为凝固剂,以CS为添加剂制备壳聚糖(CS)/聚己内酯(PCL)-聚乳酸(PLA)三维多孔支架,研究了聚合物质量比对支架结构、形貌、孔隙率、力学性能和降解性能的影响。实验结果表明,CS和基体存在相互作用,CS有利于形成三维相互贯通的微孔结构,但CS的存在会使基体中各组分的熔点降低。随着PCL和PLA用量比例的改变,孔径范围和微孔形貌发生了一系列的变化。当PCL∶PLA为2∶4和3∶3时,所制备的支架孔隙率均大于90%,当进一步增大PCL质量比时,孔隙率迅速下降。抗压测试表明,所制备的支架弹性模量为0.8～8.0 MPa。降解性能分析表明,4周以后,当PCL∶PLA为3∶3时,质量损失率最大,达到5.94%。该分析表明采用相分离法,通过调节PCL和PLA的质量比可制备形貌、孔隙率、降解速率和力学性能满足要求的三维多孔支架材料,有望应用在软骨组织工程上。     

Evaluation of oriented poly(lactide) polymers vs. existing PET and oriented PS for fresh food service containers

Poly(lactide) (PLA) polymers have garnered increasing attention in the last few years as food packaging materials because they can be obtained from renewable resources; their production consumes quantities of carbon dioxide; they can be recycled and composted; and their physical and mechanical properties can be tailored through polymer architecture. As a consequence, PLA is becoming a growing alternative as a ‘green’ food packaging material. PLA's optical, physical and mechanical properties have been compared to those of polystyrene (PS) and polyethylene terephthalate (PET), although studies comparing and showing the actual performance of PLA, PS and PET plastics containers are scarce. The purpose of this study was to investigate and compare the role of PLA in package sustainability for the food service industry. Two of the commonly used materials to make containers to package fresh food, PET and oriented polystyrene (OPS), were compared with oriented PLA (OPLA) and OPLA with 40% recycled content from the industrial trimming process. The recycled OPLA provides an opportunity for full material utilization and lower costs. This study involved a number of tests to quantify the physical, mechanical, barrier and compatibility properties that would affect the selection criteria for containers to be used for food service applications. Based on the data collected, OPLA, OPLA + 40% regrind, OPS and PET performances were evaluated. Exposure of the four materials to vegetable oil and weak and strong acids show a minimal reduction in the performance of these polymers. At ambient temperature, PET has the highest impact resistance, followed by OPLA, OPS and OPLA + 40% regrind. In terms of barrier properties, PET shows the highest oxygen barrier, followed by OPLA, OPLA 40% recycled content, and OPS. Thus, OPLA and OPLA with 40% recycled content can be used for fresh food applications as well as OPS and PET, and in many situations it performs better than OPS and PET. Copyright © 2005 John Wiley & Sons, Ltd.     

软骨细胞在聚乳酸支架中的体外生长行为

采用明胶和氯化钠颗粒作为致孔剂,使用溶剂浇铸／颗粒沥滤法制备了高孔隙率、孔间连通和高机械性能的聚乳酸支架,采用软骨细胞体外培养研究了这两种多孔支架对细胞生长性能的影响．结果表明,软骨细胞在以明胶颗粒为致孔剂制备的多孔支架中的相对数量和GAG的分泌量更多,细胞的活性更高。     

聚(3-羟基丁酸酯-3-羟基戊酸酯)/聚碳酸亚丙酯复合支架的构建与表征

分别采用反应性和非反应性熔融共混方法结合粒子沥滤技术以及碱处理技术构建不同质量比的聚(3-羟基丁酸酯-3-羟基戊酸酯)(PHBV)/聚碳酸亚丙酯(PPC)复合支架,通过表征支架的表面形态、孔隙率大小和体外降解性能,发现反应性共混法可显著改善支架的相容性和界面粘接。非反应性熔融共混法构建的支架孔隙率高于反应性共混法构建的复合支架。随着PPC含量的升高,复合支架的孔隙率升高。当PHBV/PPC质量比达50/50时,支架在PBS缓冲液中降解最快,反应性共混法构建的支架亲水性高于非反应性共混法,碱处理技术可显著改善复合支架的亲水性。这对功能重建的体内研究和临床实践具有潜在的理论价值和应用前景。     

Preparation of poly(3-hydroxybutyrate)/nano-hydroxyapatite composite scaffolds for bone tissue engineering

Poly(3-hydroxybutyrate)/nano-hydroxyapatite (PHB/nHA) composite scaffolds were fabricated via powder mixing, compression moulding, and particle leaching technique. The scaffolds had high porosity with interconnected porous architecture, a favorable structure for cell attachment and new bone tissue ingrowth. A homogeneous dispersion and a uniform distribution of HA nanoparticles in the polymer matrix were obtained. The scaffolds exhibited improved compressive modulus and compressive strength, which were all in the range of compressive modulus and compressive strength of cancellous bone. In addition, the use of toxic organic solvents was eliminated. Thus, the fabricated PHB/nHA composite scaffolds tend to be promising for application in bone tissue engineering.     

Injectable and Crosslinkable PLGA‐Based Microribbons as 3D Macroporous Stem Cell Niche

Poly(lactide‐co‐glycolide) (PLGA) has been widely used as a tissue engineering scaffold. However, conventional PLGA scaffolds are not injectable, and do not support direct cell encapsulation, leading to poor cell distribution in 3D. Here, a method for fabricating injectable and intercrosslinkable PLGA microribbon‐based macroporous scaffolds as 3D stem cell niche is reported. PLGA is first fabricated into microribbon‐shape building blocks with tunable width using microcontact printing, then coated with fibrinogen to enhance solubility and injectability using aqueous solution. Upon mixing with thrombin, firbornogen‐coated PLGA microribbons can intercrosslink into 3D scaffolds. When subject to cyclic compression, PLGA microribbon scaffolds exhibit great shock‐absorbing capacity and return to their original shape, while conventional PLGA scaffolds exhibit permanent deformation after one cycle. Using human mesenchymal stem cells (hMSCs) as a model cell type, it is demonstrated that PLGA μRB scaffolds support homogeneous cell encapsulation, and robust cell spreading and proliferation in 3D. After 28 days of culture in osteogenic medium, hMSC‐seeded PLGA μRB scaffolds exhibit an increase in compressive modulus and robust bone formation as shown by staining of alkaline phosphatase, mineralization, and collagen. Together, the results validate PLGA μRBs as a promising injectable, macroporous, non‐hydrogel‐based scaffold for cell delivery and tissue regeneration applications.     

单模聚焦微波辐射酶促合成PLA-PEG-PLA三嵌段共聚物

采用Discover微波精确有机合成系统及其单模聚焦微波辐射技术与空压气体同步冷却技术,分别以脂肪酶和辛酸亚锡为催化剂,聚乙二醇(PEG)为大分子引发剂引发消旋丙交酯(D,L-LA)开环聚合制备PLA-PEG-PLA共聚物,通过正交实验研究了功率、催化剂种类和用量、时间和温度对共聚物产率的影响,确定了最佳合成条件.在此...     

PBS增韧改性MWNTs/PLA导电3D 打印耗材的制备及性能

为解决多壁碳纳米管/聚乳酸(MWNTs/PLA)导电打印耗材变脆的问题,本文利用双螺杆熔融共混方法,制备了聚丁二酸丁二醇酯(PBS)增韧改性的MWNTs/PLA复合材料。研究发现,PBS添加量对复合材料的性能有显著影响。随PBS含量增加,复合材料的电阻率升高,断裂伸长率和冲击强度明显提高,但拉伸强度、弯曲强度和硬度有所降低。当PBS含量为10%时,共混复合材料的综合性能最好,并根据最佳条件制成具有一定韧性的导电3D打印耗材,实际使用效果良好。     

3D printing for soft robotics – a review

Soft robots have received an increasing attention due to their advantages of high flexibility and safety for human operators but the fabrication is a challenge. Recently, 3D printing has been used as a key technology to fabricate soft robots because of high quality and printing multiple materials at the same time. Functional soft materials are particularly well suited for soft robotics due to a wide range of stimulants and sensitive demonstration of large deformations, high motion complexities and varied multi-functionalities. This review comprises a detailed survey of 3D printing in soft robotics. The development of key 3D printing technologies and new materials along with composites for soft robotic applications is investigated. A brief summary of 3D-printed soft devices suitable for medical to industrial applications is also included. The growing research on both 3D printing and soft robotics needs a summary of the major reported studies and the authors believe that this review article serves the purpose.     

Enhanced mechanical properties of linear segmented shape memory poly(urethane-urea) by incorporating flexible PEG400 and rigid piperazine

The goal of this study is to design and synthesize a linear segmented shape memory poly(urethane-urea) (SMPUU) that possesses near-body-temperature shape memory temperature (T_tran) and enhanced mechanical properties by incorporating flexible poly(ethylene glycol) 400 (PEG400) to form poly(D,L-lactic acid)-based macrodiols (PDLLA--PEG400--PDLLA) and then rigid piperazine (PPZ) as a chain extender to form the desired SMPUUs (PEG400--PUU--PPZ). PEG400 increased M_n while maintaining a lower T_g of PDLLA--PEG400--PDLLA, which together with PPZ improved the mechanical properties of PEG400--PUU--PPZ. The obtained optimum SMPUU with enhanced mechanical properties (σ_y = 24.28 MPa; ?_f = 698%; U_f = 181.5 MJ/m³) and a T_g of 40.62°C exhibited sound shape memory properties as well, suggesting a promising SMPUU for in vivo biomedical applications.     

PEG交联有机硅/陶瓷杂化膜的制备及反渗透脱盐性能

采用聚乙二醇(PEG)和1,2-双(三乙氧基硅基)乙烷(BTESE)进行交联共聚, 以多孔α-Al₂O₃陶瓷膜为支撑体制备了一系列PEG交联的有机硅杂化膜。通过原子力显微镜(AFM)、场发射扫描电镜(FE-SEM)、傅里叶红外光谱(FT-IR)、热重分析(TGA)和水接触角测试(CA)对膜结构和物化性质进行了表征。将制备的BTESE/PEG杂化膜应用于反渗透脱盐, 考察了PEG含量、操作压力、进料浓度和操作温度等因素对改性杂化膜分离性能的影响。实验结果表明, 相比于未改性的BTESE膜, 10wt% PEG交联的有机硅杂化膜BTESE/PEG-10的水渗透率和盐离子表观截留率均有所提高。随着操作压力的升高和进料盐含量的下降, NaCl截留率上升而水渗透率基本恒定。在高达70℃的温度循环实验中, BTESE/PEG-10杂化膜表现出优异的水热稳定性, NaCl表观截留率始终保持在97%以上, 水渗透率高达1.2×10^-12 m³/(m²·s·Pa)。     

一种生物可降解材料PDLLA-(MAh-PEG)_n-PDLLA的合成与表征

丙交酯(LA)开环聚合时同时引入功能性单体合成含活性基团的可降解聚合物,是目前对聚乳酸(PLA)类材料进行改性的一个重要研究方向。文中首先以聚乙二醇(PEG)和马来酸酐(MAh)为原料,采用溶液缩聚法制得聚乙二醇与马来酸酐的交替预聚物(MAh-PEG)n;然后以辛酸亚锡为催化剂,(MAh-PEG)n为引发剂,引发D,L-丙交酯(D,L-LA)开环聚合,制得聚(D,L-乳酸)(PDLLA)与(MAh-PEG)n的共聚物PDLLA-(MAh-PEG)n-PDLLA。采用凝胶渗透色谱(GPC)、傅里叶红外(FT-IR)、核磁共振(NMR)等方法对共聚物的结构和性质进行研究。结果发现,随着(MAh-PEG)n用量的增加,共聚物的分子量有所下降。这种聚合物的主链含有不饱和双键和亲水性的链段,预计将成为一种新的生物可降解材料。