3D printing of personalized polylactic acid scaffold laden with GelMA/autologous auricle cartilage to promote ear reconstruction

At present,the clinical reconstruction of the auricle usually adopts the strategy of taking autologous costal cartilage.This method has great trauma to patients,poor plasticity and inaccurate shaping.Three-dimensional(3D)printing technology has made a great breakthrough in the clinical application of orthopedic implants.This study explored the combination of 3D printing and tissue engineering to precisely reconstruct the auricle.First,a polylactic acid(PLA)polymer scaffold with a precisely customized patient appearance was fabricated,and then auricle cartilage fragments were loaded into the 3D-printed porous PLA scaffold to promote auricle reconstruction.In vitro,gelatin methacrylamide(GelMA)hydrogels loaded with different sizes of rabbit ear cartilage fragments were studied to assess the regenerative activity of various autologous cartilage fragments.In vivo,rat ear cartilage fragments were placed in an accurately designed porous PLA polymer ear scaffold to promote auricle reconstruction.The results indicated that the chondrocytes in the cartilage fragments could maintain the morphological phenotype in vitro.After three months of implantation observation,it was conducive to promoting the subsequent regeneration of cartilage in vivo.The autologous cartilage fragments combined with 3D printing technology show promising potential in auricle reconstruction.

Morphological, Rheological and Mechanical Properties of Pla-Typha Based Biocomposites

Due to the demand from society for the consumption of ecological polymeric materials, one of the polymers that have satisfied this request is the poly (lactic acid) (PLA). This polymer is derived from renewable resources, it is recyclable and biodegradable. It presents a good understanding between the promising properties and the cost. However, a route to increase the mechanical properties and reduce the cost of PLA is the elaboration of PLA based biocomposites by using fillers from natural waste. In this work, The effect of Typha content on the morphological, rheological, thermal and mechanical properties of PLA matrix was studied. Four formulations were produced with different mass concentrations. The results showed an increase in the viscoelastic properties, as a function of the Typha stem powder concentration. The DSC analysis showed an increase in the crystallinity rate of the various composites confirming the nucleating effect provided by the filler. TGA analysis indicated a decrease in the decomposition temperature of the composites. Mechanical tensile tests have shown a significant improvement in the mechanical properties mainly for the samples containing 45% (w/w) of Typha powder.

Design,synthesis and characterization of novel poly(urethane-urea) based on a macrodiol from poly(lactic acid) and poly(p-dioxanone)

A series of novel poly（urethane-urea）（PUU） was synthesized from poly（lactide-co-p-dioxanone） macrodiol（HO-P（LA-co-PDO）-OH）, hexamethylene diisocyanate（HDI） and butanediamine（BDA）.The obtained PUU,which is recorded as P（LA-co-PDO）-PUU here,may demonstrate enhanced phase separation and thus improved shape memory property.FTIR was employed to characterize the copolymers,and the effects of NCO/OH molar ratios on Tg of PUU was investigated by means of differential scanning calorimetry （DSC）.The results revealed the successful synthesis of P（LA-co-PDO）-PUU.In addition,the Tg of P（LA-co-PDO）-PUU increased from 37.9℃to 44.2℃with the increase NCO/OH ratios from 1.1 to 1.2.The P（LA-co-PDO）-PUU with Tg close to body temperature will have potential applications as shape memory polymers in biomedical fields,especially in minimally invasive surgery.

4D printing of PLA/PCL shape memory composites with controllable sequential deformation

Shape memory polymers(SMPs)are a promising class of materials for biomedical applications due to their favorable mechanical properties,fast response,and good biocompatibility.However,it is difficult to achieve controllable sequential shape change for most SMPs due to their high deformation temperature and the simplex deformation process.Herein,shape memory composites based on polylactic acid(PLA)matrix and semi-crystalline linear polymer polycaprolactone(PCL)are fabricated using 4D printing technology.Compared with pure PLA,with the rise of PCL content,the 4D-printed PLA/PCL composites show decreased glass transition temperature(Tg)from 67.2 to 55.2°C.Through the precise control of the deformation condition,controllable sequential deformation with an outstanding shape memory effect can be achieved for the PLA/PCL shape memory composites.The response time of shape recovery is less than 1.2 s,and the shape fixation/recov-ery rates are above 92%.In order to simulate sequential petal opening and sequential drug releasing effects,a double-layer bionic flower and a drug release device,respectively,are presented by assembling PLA/PCL samples with different PLA/PCL ratios.The results indicate the potential applications of 4D-printed PLA/PCL composites in the field of bio-inspired robotics and biomedical devices.

Catalytic Cracking of Polylactic Acid to Acrylic Acid

Comprehensive Summary,As a typical type of sustainable plastic,polyesters can be recycled or upcycled into value-added chemicals in a variety of methods.However,excess reagents are required for most of the depolymerization and upcycling processes,causing the emission of environmental pollutants and the waste of chemical resources.Here we demonstrate a one-pot catalytic process to directly crack polylactic acid into acrylic acid by acid catalyst with the assistance of an ionic liquid,Bu4PBr.Polylactic acid is attacked by the Br–from Bu4PBr and the H+from acid to form oligomers containing Br or acryloyl group,and these oligomers serve as intermediates to produce acrylic acid during their mutual transformation.The acrylic acid is vaporized directly from the reactor and obtained in a collector with a selectivity around 90%when polylactic acid is fully converted.This green process shows great advantages in atom economy compared to the conventional recycling/upcycling methods for polyesters,in addition.

Polyethylene glycol/polylactic acid block co‐polymers as solid–solid phase change materials

Phase change materials(PCMs)are promising thermal energy storage materials due to their high specific latent heat.Conventional PCMs typically exploit the solid–liquid(s–l)transition.However,leakage and leaching are common issues for solid–liquid PCMs,which have to be addressed before usage in practical applications.In contrast,solid–solid(s–s)PCMs would naturally overcome these issues due to their inherent form stability and homogeneity.In this study,we report a new type of s–s PCM based on chemically linked polyethylene glycol(PEG,the PCM portion)with polylactic acid(PLA,the support portion)in the form of a block co‐polymer.Solid‐solid latent heat of up to 56 J/g could be achieved,with melting points of between 44°C and 55°C.For comparison,PEG was physically mixed into a PLA matrix to form a PEG:PLA composite.However,the composite material saw leakage of up to 9%upon heating,with a corresponding loss in thermal storage capacity.In contrast,the mPEG/PLA block co‐polymers were found to be completely homogeneous and thermally stable even when heated above its phase transition temperature,with no observable leakage,demonstrating the superiority of chemical linking strategies in ensuring form stability.

In vitro Degradation Study of a Braided Thin-Walled Biodegradable Ureteral Stent

The main disadvantage of conventional ureteral stents commonly used to provide urinary drainage after urological practice is that the patients have to undergo a secondary surgical procedure to remove stents. A new braided thin-walled biodegradable ureteral stent composed of PGA （ polyglycolic acid） and PLGA （ eopolymer of polylactic and polygiycolic acid） mnltifilaments was evaluated in v/tro in this study. In vitro degradation was performed in artificial urine with pH of 5.8 and the temperature of 37~C. The mass loss, mechanical properties, and morphology were observed at different degradaing time intervals of 0, 1, 2, 3, 4, and 5 weeks. The stent had a thinner wail than those of other degradable stents and provided better mechanical properties. The braided thin-walled biodegradable ureteral stents began to degrade after 2 weeks. At the week of 5, the stents were fully degraded. The degradative process of stents is smooth and well controlled.

Properties of Scaffold Reinforcement for Tendon Tissue Engineering in vitro Degradation

Four kinds of braided yarns were produced with different proportions of polyglycolic acid( PGA) and polylactic acid( PLA)multifilaments( 2PGA /1PLA, 2PGA /2PLA, 3PGA /1PLA, and3PGA /2PLA). A novel artificial plain stitch scaffold reinforcement was manufactured by braiding technology and knitting technology respectively. Tendon scaffold reinforcements were investigated for 8weeks in phosphate buffered solution( PBS)( pH = 7. 4) at 37 ℃.The degradation was studied with regard to the mass loss,tensile properties,grams per square meter( g /m2),thickness,caliber,and porosity of scaffold reinforcements. The experimental showed that during the process of 8-week degradation,the mass losses of scaffold reinforcements were small in the first 3-week,but they increased rapidly after 3-week,and the speeds tended to be small gradually after 6-week; the tensile properties dropped rapidly in the first 2-week; the grams per square meter and thicknesses speeded down obviously between 3-week to 6-week. The caliber and porosity of scaffold reinforcements first decreased and then increased gradually. The porosity can reach more than 97%.

Morphological Evaluation of PLA/Soybean Oil Epoxidized Acrylate Three-Dimensional Scaffold in Bone Tissue Engineering

Tissue engineering’s main goal is to regenerate or replace tissues or organs that have been destroyed by disease,injury,or congenital disabilities.Tissue engineering now uses artificial supporting structures called scaffolds to restore damaged tissues and organs.These are utilized to attach the right cells and then grow them.Rapid prototyping appears to be the most promising technology due to its high level of precision and control.Bone tissue replacement“scaffolding”is a common theme discussed in this article.The fused deposition technique was used to construct our scaffold,and a polymer called polylactic acids and soybean oil resin were used to construct our samples.The samples were then divided into two groups;the first group was left without immersion in the simulated body fluid and served as a control for comparison.The second group was immersed in the simulated body fluid.The results of the Field Emission Scanning Electron Microscope(FESEM),Energy Dispersive X-ray Spectroscopy(EDX)and X-ray diffraction(XRD)were utilized to interpret the surface attachment to ions,elements,and compounds,giving us a new perspective on scaffold architecture.In this study,an innovative method has been used to print therapeutic scaffold that combines fused deposition three-dimensional printing with ultraviolet curing to create a high-quality biodegradable polymeric scaffold.Finally,the results demonstrate that adding soybean oil resin to the PLA increased ion attachment to the surface while also attracting tricalcium phosphate formation on the surface of the scaffold,which is highly promising in bone tissue replacement.In conclusion,the soybean oil resin,which is new in the field of bone tissue engineering,shows magnificent characteristics and is a good replacement biopolymer that replaces many ceramic and polymeric materials used in this field that have poor morphological characteristics.

高性能聚乙醇酸物理改性研究及应用进展

高性能生物降解材料聚乙醇酸(PGA)存在柔韧性差、加工困难和降解速率快等问题,物理改性是一种能够有效提高其综合性能且显著降低成本的简单易行的方法。主要综述了近十几年来国内外针对PGA性能缺陷及加工问题开展的共混改性研究进展,以及满足不同加工和应用要求的高性能PGA的改性技术与方法。添加物主要包括功能性助剂、可降解高分子聚合物及不可降解高分子聚合物,共混改性有效地提升了PGA的热稳定性、力学特性和生物相容性,调控了PGA的降解速率,并提升了PGA共混体系的相容性。

生物降解高分子材料阻燃改性研究进展

为了探讨生物降解高分子材料阻燃改性研究进展情况,梳理了近年来化学合成的生物降解高分子类材料阻燃性研究的文献,重点综述了聚丁二酸丁二醇酯和聚乳酸的阻燃改性研究情况。聚丁二酸丁二醇酯的阻燃改性方法主要分为含磷复合协效阻燃体系和添加生物质阻燃剂两类,聚乳酸的阻燃改性方法主要分为磷系阻燃体系、磷-氮协同阻燃体系、膨胀型阻燃体系和添加生物质阻燃剂等。通过总结和分析各阻燃方法的发展状况,认为:含磷有机化合物或者磷-氮协同型阻燃剂仍然是行之有效且普遍采用的阻燃添加剂,但是这些物质的存在对于生物降解性必然产生负面影响。因此,应强化全生物质阻燃体系的构建及其应用,重点平衡阻燃性、生物降解性与加工-应用性能之间的关系,以推动生物降解高分子材料的绿色阻燃技术发展和应用。

口罩过滤材料及其驻极技术的研究进展

综述了口罩的发展历史及其核心过滤层聚合物非织造布种类和相应驻极技术的最新进展,其中驻极工艺包括电晕充电、水驻极和静电纺丝等,需要辅以驻极添加剂,常用的聚合物非织造过滤材料主要有聚丙烯和聚乳酸。同时,对其未来的发展趋势进行了展望。

暂堵剂用聚乳酸/聚乙醇酸复合纤维的制备及降解性能研究

暂堵剂是石油气开采中增产的重要材料,随着环保要求的提高,可降解暂堵剂材料已成为当前石油气开采中的首选材料。聚乙醇酸作为降解速率最快且最简单的线性脂肪族聚酯,由其制成的可降解暂堵绳结已在石油气开采中得到应用。但聚乙醇酸存在降解速率快、货架期短等问题,大大限制了其产品的推广使用。本工作采用复合熔融纺丝法制备了以聚乳酸为皮层、聚乙醇酸为芯层的圆形截面皮芯复合纤维,研究了不同皮芯比例聚乳酸/聚乙醇酸复合纤维的形貌、降解性能、热性能和结晶性。结果表明:复合纤维在70℃下的溶解率“转折点”出现在降解6 h时,降解前6 h内,复合纤维的溶解率都在3%(质量分数)以内;降解6 h后,复合纤维的溶解率几乎呈线性升高,皮芯比例为20/80的复合纤维降解24 h后,溶解率可以达到23.2%。扫描电镜照片显示,复合纤维降解24 h后,聚乳酸层厚度越小,纤维降解程度越高,在皮芯比例为20/80的复合纤维中,聚乳酸层大量开裂,造成芯层的聚乙醇酸沿纤维轴向降解断裂成小段。热性能结果显示,聚乳酸结晶度随降解时间延长而增大,而聚乙醇酸结晶度随降解时间延长先增大后减小。广角X射线衍射结果显示,复合纤维中聚乙醇酸晶粒尺寸较小,尤其是c轴长度仅为约34 nm。纤维强度保持率和降解液的pH值都与皮层厚度成正比。本工作为暂堵剂制备提供了新途径。

新型可溶暂堵绳结性能及应用研究

为考察暂堵绳结尺寸对封堵性能的影响,以可降解材料聚乳酸(PLA)、聚乙醇酸(PGA)熔融纺丝制备暂堵绳结,考察了暂堵绳结直径、尾翼长度和尾翼条数对其封堵性能的影响,并研究了PGA/PLA质量比对暂堵绳结降解性能和承压性能的影响。结果表明,在90℃条件下,随绳结尺寸增加封堵率整体呈先提高再稳定后降低的规律,当绳结直径大于18 mm、尾翼条数超过6条、尾翼长度在35~50 mm范围内时封堵性能最佳;绳结降解率随PGA/PLA质量比的增大而增大,绳结承压能力与PGA/PLA质量比成反比,当PGA/PLA质量比为80/20时,绳结在清水中26 h完全溶解,在0.1%滑溜水和30000 mg/L的盐水中23 h降解率可达100%,承压能力在PGA/PLA质量比为50/50时可达50 MPa。

生物降解聚己二酸丁二醇酯的制备及改性聚乙醇酸研究

聚乙醇酸(PGA)作为煤基生物可降解高分子材料,有着优异的力学性能和阻隔性能,但较差的韧性使得它难以大规模应用。本文设计了一种生物可降解聚酯聚己二酸丁二醇酯(PBA),并用其实现了PGA的显著增韧。以1,6-己二酸(AA)和1,4-丁二醇(BDO)为原料,在高真空条件下通过熔融缩聚制备了PBA,核磁共振波谱、傅里叶变换红外光谱和凝胶渗透色谱证明了PBA的成功制备,PBA的重均分子量为62506,多分散性指数为2.1。通过熔融共混将PBA、PGA和环氧扩链剂共混以增韧PGA,扫描电子显微镜(SEM)表明,环氧扩链剂可显著提高PGA与PBA的相容性,增容过后PBA分散相的粒径尺寸明显减小。力学性能表明,当加入环氧扩链剂和50 phr的PBA增韧后,PGA的拉伸强度能可达(48.6±2.5)MPa,断裂伸长率达458.3%±23.9%,缺口冲击强度(126.3±7.7)kJ/m^(2),断裂伸长率和缺口冲击强度较PGA纯样分别提高了43倍和46倍。

煤基聚乙醇酸技术进展

从煤化工发展的角度分析了开发聚乙醇酸产品的重要性,介绍了聚乙醇酸优异的阻隔性能、机械加工性能、生物可降解性、广泛用途以及工业化进展状况。比较了国内外聚乙醇酸树脂的各种制备方法与工艺,重点论述了直接缩聚法和乙交酯开环缩聚法两种工艺路线中催化剂的选择以及聚合条件的控制,并介绍了聚乙醇酸树脂的多种改性应用方法。此外,结合我国聚乙醇酸发展状况,讨论了开发聚乙醇酸新材料的紧迫性,同时对其前景进行了展望。

聚乳酸增韧研究进展

总结了聚乳酸增韧改性方面的最新研究进展,为新型聚乳酸复合材料的研究开发提供理论依据;概述了共混、复合、共聚、交联、增塑以及添加成核剂等几种增韧技术,并比较了不同增韧方法的特点;通过对合成方法的改进以及进行共混、共聚、复合及增塑等改性,可以显著改善聚乳酸材料的力学性能并同时保持耐热性和降解性能不受影响;开发更加高效的增韧改性剂,增加其与聚乳酸分子链间的界面相互作用并提高复合材料的冲击性能已成为研究工作的努力方向。从微观分子尺度上对聚乳酸进行增韧改性以及设计绿色合成路线仍是目前研究工作的重点。

聚羟基乙酸及其共聚物

对聚羟基乙酸及其共聚物的合成方法 ,生物降解性 ,生物相容性 ,力学性能 ,共聚改性等方面的研究进展做了综述 。

聚乳酸聚羟基乙酸共聚物涂层雷帕霉素洗脱支架对小型猪冠状动脉内膜增生的影响

目的:评价生物可降解的聚乳酸聚羟基乙酸共聚物(PLGA)涂层雷帕霉素洗脱支架对健康小型猪冠状动脉内膜增生的影响。方法:26只健康小型猪随机分入316L不锈钢裸金属支架组(316 L组)、L605钴铬合金裸金属支架组(L605组)、PLGA涂层L605支架组(PLGA组)和PLGA涂层雷帕霉素洗脱支架组(雷帕霉素组)。各组均包括1周观察终点的猪1只和4周观察终点的猪5只。雷帕霉素组还包括12周观察终点的猪2只。每只猪于左前降支和右冠状动脉各置入同种支架1枚。至观察终点时复查冠状动脉造影并处死取材,通过形态学方法观察内膜增生情况。结果:4周时反映内膜增生的各项指标雷帕霉素组均显著优于其它3组,而其它3组之间没有显著性差异。雷帕霉素组与316L组相比支架上内膜厚度少73%(0.11 mm对0.41 mm),支架间内膜厚度少79%(0.06 mm对0.29 mm),新生内膜面积少69%(0.64 mm2对2.09 mm2),面积狭窄百分比少61%(18.53%对47.27%)。316L组有4例、L605组有3例发生支架内狭窄,而雷帕霉素组无支架内狭窄发生。12周时雷帕霉素组内膜增生有所加重,但较4周时相比除了支架间内膜厚度外其他反映内膜增生的各项指标差异均无统计学意义。结论:采用可降解的PLGA涂层雷帕霉素洗脱支架可以显著抑制健康小型猪冠状动脉支架置入术后4周和12周的内膜增生。

D,L-乳酸、L-乳酸、羟基乙酸的均聚物及共聚物的结晶性能研究

合成了高分子量的聚D,L-乳酸、聚L-乳酸、聚羟基乙酸、D,L-乳酸和L-乳酸的共聚物以及乙酸和D,L-乳酸共聚物。以WAXD、FT-IR、DTA表征了上述系列聚合物的结晶性能,分析了单体种类和共聚物中单体的比例对聚合物中结晶性能的影响,并对该系列聚合物的晶区结构作了描述。用万能拉力计测试了PLA系列聚合物的力学性能,以DTA测定了PGLA系列聚合物的热性能,探讨通过调整聚合物的组成以改变其结晶特性来调控聚合物的力学性能和加工性能的途径。