可生物降解PLA／PCL,PELA／PECL共混体系的研究

本工作以DSC研究了聚d,l-乳酸/聚ε-己内酯(PLA/PCL)、聚d,l-乳酸-聚乙二醇嵌段共聚物/聚ε-己内酯-聚乙二醇嵌段共聚物(PELA/PECL)共混体系的相容性,发现PLA/PCL体系是不相容的,随PLA含量的增大,PCL结晶度增大。而PELA/PECL共混体系中,由于PEG链段的“内增容作用”,使二组分有较好的相容性。随PELA含量的增加,PECL的熔点、结晶度降低。     

组织工程及周围神经修复

综述了组织工程的发展历史。通过对神经系统的结构,功能和特点的说明,论述了周围神经的不同损伤和修复方法;分析和比较了用生物可吸收性神经诱导管,生物惰性高分子神经诱导管,自体神经和无诱导修复等不同的神经修复方法和修复材料对大鼠坐骨神经修复的结果,提出了周围神经修复组织工程用的理想材料和结构要求。     

皮肤诱导再生材料的研究进展与挑战

烧伤、机械创伤等导致的皮肤缺损及功能丧失是常见的临床难题之一。介绍了皮肤缺损修复的研究背景和皮肤修复材料的发展历史。通过对国内外原位诱导皮肤再生材料研究现状的分析,总结了影响皮肤诱导再生材料性能的关键科学问题,即原位诱导血管化与原位诱导细胞迁移,并归纳介绍了相应的材料设计与改性方法。最后根据皮肤诱导再生材料存在的不足对未来皮肤诱导再生材料的研究与发展进行了展望。     

多因素对再生复合掺料基地聚物混凝土抗压强度的影响

大量的建筑废弃物给环境带来了严重负担,本工作利用建筑废弃物制备而成的再生复合掺料替代地聚物混凝土中的粉煤灰,以实现建筑废弃物的再生利用.试验研究了养护条件、氢氧化钠浓度以及再生复合掺料替代率对再生复合掺料基地聚物混凝土抗压强度的影响,并利用SEM对混凝土微观形貌进行对比分析.研究结果表明,再生复合掺料对地聚物混凝土的和易性有不利影响,但与基准混凝土相比,替代率为20％～60％(质量分数,下同)的再生复合掺料基地聚物混凝土的抗压强度有所提高.高温养护能提高混凝土的抗压强度,与常温养护相比,3 d、7 d和28 d抗压强度分别平均提高了198.5％、104.0％和52.6％.氢氧化钠浓度对不同替代率的再生复合掺料基地聚物混凝土的影响不同,在低替代率(0％～40％)时,混凝土抗压强度随氢氧化钠浓度的增加而增加;在高替代率(60％～100％)时,混凝土抗压强度随氢氧化钠浓度的增加先增加后降低.因此再生复合掺料应用于地聚物混凝土中部分替代粉煤灰是可行的.     

大鼠骨髓间充质干细胞与β-磷酸三钙/聚L-乳酸支架材料的复合

将成骨诱导前后的大鼠骨髓间充质干细胞与不同比例、不同孔径和不同孔隙率的βTCP／PLLA材料复合，通过体内体外实验研究β-磷酸三钙／聚L-乳酸（β-TCP／PLLA）的成分、孔径和孔隙率等结构参数对复合材料在体内异位成骨能力的影响．结果表明，β-TCP／PLLA成分比为2：1，致孔剂含量为70％；孔径为200-450μm的支架材料在体外更有利于细胞的生长、增殖以及分化．这种支架材料在裸鼠体内具有异位成骨的能力，成骨诱导后的大鼠骨髓间充质干细胞比没有诱导的细胞更适合作为种子细胞．     

不同pH条件下再生纤维表面的CPAM/CMC静电逐层自组装

利用静电逐层自组装技术,在再生纤维表面沉积了阳离子聚丙烯酰胺（CPAM）/羧甲基纤维素（CMC）复合膜。研究了不同pH条件下CPAM/CMC在再生纤维表面的静电吸附规律。采用FT-IR、SEM和Zeta电位测试对再生纤维表面的聚电解质多层膜进行表征,而再生纤维力学性能用纸页的裂断长和耐破指数来评价。研究表明,CPAM/...     

D,L-乳酸-均苯三酚星形聚合物的合成与表征

以廉价易得的D,L-乳酸和均苯三酚为原料,采用工艺简单、成本低廉的直接熔融聚合法合成了星形聚D,L-乳酸(SPDLLA).用特性黏度[η]、FTIR、1H NMR、GPC、XRD等手段对聚合物的结构与性能进行了表征,Mw 最高可达到7600,并发现所合成的SPDLLA的Tg、Tm均小于线形聚D,L-乳酸(LPDLLA)的Tg、Tm.     

中枢神经再生材料研究进展

首先介绍了目前中枢神经再生面临的问题和应对策略,然后系统地综述了脑再生和脊髓再生修复材料的发展。研究发现,成人中枢神经系统内存的神经干细胞和具有特定分化方向的前体细胞具有潜在的、巨大的修复功能;生物支架材料与神经干细胞的联合使用能够较好地控制细胞微环境,有望提高细胞移植后的存活状况,促进中枢神经再生。最后,结合现在中枢神经再生的研究热点——神经干细胞,阐述了中枢神经再生材料调控干细胞的研究进展和潜能,为联合应用生物材料与干细胞促进中枢再生提供了参考。     

高分子量聚L-乳酸的合成和表征

采用丙交酯开环聚合合成聚L-乳酸(PLLA),研究了引发剂用量、聚合时间对聚L-乳酸分子量的影响.采用FTIR、DSC、TG分析方法对聚乳酸的结构和热性能加以表征.研究结果表明通过对聚合时间以及引发剂用量的控制,合成出高分子量聚L-乳酸.FTIR分析结果证实了聚L-乳酸的结构,DSC分析表明合成出的聚L-乳酸玻璃化转变温度为62℃,结晶度达到42.3%;TG分析表明聚L-乳酸热分解温度为299℃.     

钢管地聚物再生混凝土短柱轴压荷载下的实验研究

地聚物再生混凝土(Geopolymeric recycled concrete,GRC)是一种考虑环境可持续发展的新型建筑材料,它是利用粉煤灰激发的碱溶液完全代替水泥,同时利用再生粗骨料完全或部分代替天然粗骨料制作而成的新型混凝土材料。地聚物再生混凝土可以用在钢管结构中,称为钢管地聚物再生混凝土构件。该文对12根钢管地聚物再生混凝土短柱进行了一系列实验研究,实验设计主要考虑了2种不同钢管界面尺寸、不同混凝土类型(普通再生混凝土、地聚物再生混凝土)以及不同再生骨料取代率(0%、50%、100%)。通过实验研究考察了构件在轴压荷载作用下的荷载-应变关系,对比分析了各构件的极限承载力和失效机理,并且通过延性指标(DI)对比分析了各个钢管短柱在轴压荷载作用下的延性行为表现。结果表明,随着钢管核心混凝土中再生粗骨料的增多,钢管地聚物再生混凝土和钢管再生混凝土的极限承载力随之降低。再生粗骨料的含量对钢管地聚物再生混凝土短柱的力学行为表现影响更大。最后,依照各规程的理论计算方法对本实验结果进行了比较,进一步探讨了各规程对计算钢管再生混凝土和钢管地聚物再生混凝土柱承载力的适用性。     

医用聚乳酸的合成及其管型材料性能的测定

本文以无毒的辛酸亚锡作催化剂,将丙交酯聚合成聚乳酸(PLA)。研究了在760～0.05mmHg范围内压力改变对PLA分子量的影响,并将PL制成内径为2mm的管型材料,经热稳定性、机械强度和降解性能等试验,结果都表明此管材可用作引导神经再生导管材料。     

A Poly(lactide) Stereocomplex Structure with Modified Magnesium Oxide and Its Effects in Enhancing the Mechanical Properties and Suppressing Inflammation

Biodegradable polymers such as poly(l ‐lactide) (PLLA) have been widely utilized as materials for biomedical applications. However, the relatively poor mechanical properties of PLLA and its acid‐induced cell inflammation brought about by the acidic byproducts during biodegradation pose severe problems. In this study, these drawbacks of PLLA are addressed using a stereocomplex structure, where oligo‐d ‐lactide‐grafted magnesium hydroxide (MgO‐ODLA) is synthesized by grafting d ‐lactide onto the surface of magnesium hydroxide, which is then blended with a PLLA film. The structure, morphology, pH change, thermal and mechanical properties, in‐vitro cytotoxicity, and inflammation effect of the MgO‐ODLAs and their PLLA composites are evaluated through various analyses. The PLLA/MgO70‐ODLA30 (0–20 wt%) composite with a stereocomplex structure shows a 20% increase in its tensile strength and an improvement in the modulus compared to its oligo‐l ‐lactide (PLLA/MgO70‐OLLA30) counterpart. The interfacial interaction parameter of PLLA/MgO70‐ODLA30 (5.459) has superior properties to those of PLLA/MgO70‐OLLA30 (4.013) and PLLA/Mg(OH)₂ (1.774). The cell cytotoxicity and acid‐induced inflammatory response are suppressed by the neutralizing effect of the MgO‐ODLAs. In addition, the inflammatory problem caused by the rapid acidification of the stereocomplex structure is also addressed. As a result, the stereocomplex structure of the MgO‐ODLA/PLLA composite can be used to overcome the problems associated with the biomedical applications of PLLA films.     

Comparison of the degradability of poly(lactide) packages in composting and ambient exposure conditions

The adoption of biodegradable polymeric materials is increasing in food and consumer goods packaging applications, due to concerns about the disposal of petroleum‐based polymers and the increasing cost of petroleum‐based polymer resins. Currently, poly(lactide) (PLA) polymers are the biggest commercially available bio‐based polymeric packaging materials. As the main motivation for adopting biopolymers is environmental, there is a need to address the degradability and environmental performance of biodegradable packages. The aim of this study was to investigate and compare the degradation of two commercially available biodegradable packages made of PLA under real compost conditions and under ambient exposure, using visual inspection, gel permeation chromatography, differential scanning calorimetry and thermal gravimetric analysis. A novel technique to study and track the degradability of these packages under real compost conditions was used. Both packages were subjected to composting and ambient exposure conditions for 30 days, and the degradation of the physical properties was measured at 1, 2, 4, 6, 9, 15 and 30 days. PLA bottles made of 96% l ‐lactide exhibited lower degradation than PLA delicatessen (‘deli’) containers made of 94% l ‐lactide, mainly due to their highly ordered structure and, therefore, their higher crystallinity. The degradation rate changed as the initial crystallinity and the l ‐lactide content of the packages varied. Temperature, relative humidity and pH of the compost pile played an important role in the rate of degradation of the packages. First‐order degradation kinetics and linear degradation trends were observed for both packages subjected to composting conditions. Copyright © 2006 John Wiley & Sons, Ltd.     

<Emphasis Type="Italic">In vitro</Emphasis> properties of PLLA screws and novel bioabsorbable implant with elastic nucleus to replace intervertebral disc

The suitability of two different implant types for the replacement of the intervertebral disc was studied in vitro. Self-reinforced poly-L-lactide (SR-PLLA) screws Ø 4.5 mm were studied 24 weeks in vitro and cylindrical implants with elastic nucleus made of poly(L/D)lactide 96/4, poly(L/DL)lactide 70/30, Bioactive Glass n:o 13–93 and Polyactive^® 1000PEOT70PBT30 were studied 15 weeks in vitro. The cylindrical implant mimics the size and shape of the intervertebral disc. During the in vitro, there were no changes in compression properties with either implant types. The screws had sufficient modulus for intervertebral ossification in the canine model and the cylindrical implant showed also sufficient mechanical properties. These results suggest that both implant types could be used in clinical testing.     

Preparation of nano-HA/PLA composite by modified-PLA for controlling the growth of HA crystals

In order to control the growth of hydroxyapatite (HA) crystals and obtain nano-hydroxyapatite/poly(lactide) (n-HA/PLA) composite with interfacial interaction between the two phases, PLA surfaces were modified with poly(α-methacrylic acid) (PMAA) via photooxidization and UV induced polymerization. FTIR analysis showed that the PMAA was grafted onto the PLA surface and the grafting rate increased with the grafting time. The n-HA/PLA composites were synthesized by modified-PLA and characterized by FTIR, XRD and SEM. Several analyses suggested that the m-PLA could act as a template to manipulate the nucleation and growth of n-HA crystals, control the morphology and size of n-HA crystals as well as their distribution over the organic phase.     

磷脂聚乳酸的扩链反应

研究了具有良好血液相容性的磷脂聚乳酸用异氰酸酯扩链的反应。核磁共振(1H-NMR)和红外光谱(FT-IR)结果证明扩链反应是成功的。凝胶渗透色谱(GPC)测定分子量的结果显示,磷脂聚乳酸的-Mn在扩链后增加约一倍,改变扩链反应条件,扩链磷脂聚乳酸的M-n增加倍率变化不大;纯聚乳酸扩链后-Mn增加约十倍,但纯聚乳酸在扩链反应中更容易发生交联。研究结果表明,磷脂聚乳酸的扩链反应增加分子量约一倍是由其分子结构决定的。     

Inside Front Cover: Conducting‐Polymer Nanotubes for Controlled Drug Release (Adv. Mater. 4/2006)

Martin and co‐workers report on p. 405 that nanotubes formed from the conducting polymer poly(3,4‐ethylenedioxythiophene) (PEDOT), as shown on the inside cover, can be used for the controlled release of anti‐inflammatory drugs. The fabrication process includes electrospinning of a biodegradable polymer, either poly(L ‐lactide) or poly(lactide‐co‐glycolide), into which the required drug is incorporated, followed by electrochemical deposition of the conducting polymer around the drug‐loaded electrospun nanofibers. Drug release from the nanotubes is achieved by external electrical stimulation of the nanotubes.     

Surface-acoustic-wave directional coupler for apodization of integrated acoustooptic filters

A SAW waveguide directional coupler that was used to provide a raised-cosine apodization of the SAW beam intensity, in order to achieve sidelobe suppression of an integrated acoustooptic filter, is demonstrated. The SAW guide coupler consisted of two closely spaced, evanescently coupled parallel acoustic waveguides. A single guided SAW mode was excited by a miniature transducer imbedded in a 100-mum-wide waveguide, and in excess of 99% of the SAW energy was transferred from the original waveguide to the coupled guide, and back, across a gap of 20 mum. The coupling length (for complete crossover) was 9.8 mm and depended exponentially on gap, as expected. This SAW coupler resulted in 10-dB sidelobe suppression compared to an unapodized acoustooptic filter.     

A Quantitative Method for Determination of Lactide Composition in Poly(lactide) Using (1)H NMR

A method has been developed to quantitatively determine the composition of d-lactide and meso-lactide stereoisomer impurities in poly(lactide) containing predominantly l-lactide. In this method, the stereosequence information obtained from a few well-resolved resonances in the (1)H NMR spectrum representing RR and R stereogenic defects is used. The d-lactide and meso-lactide as minor components lead to RR and R stereogenic defects, respectively, which influence the isotactic chain length distribution and hence affect the polymer properties. Analytical equations relating the stereosequence probability to the lactide feed composition are not available due the complicated kinetics involved for the melt polymerization; viz. the preference for syndiotactic lactide addition decreases with reducing residual lactide concentration in the batch process. Hence, empirical correlations were determined by least-squares fit to the predictions for the specific stereosequence probabilities provided by Monte Carlo calculations of a number of lactide stereocopolymerizations. The Monte Carlo calculations simulate the kinetics observed for melt polymerization at 180 °C catalyzed by Sn(II) bis(2-ethylhexanoate) (Sn(II) octoate) in a 1:10 000 catalyst/lactide ratio.     

Probing the cytotoxicity of CdSe quantum dots with surface modification

The cytotoxicity of CdSe quantum dots (QDs) with surface modification was reported first in the paper. CdSe QDs were incorporated into poly (d, l) lactide (PLA) nanoparticles and then surface modified with Fluronic® 68 (F-68), cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), respectively. Three different particle sizes and zeta potential of the surface modified CdSe QDs were produced using a nano-precipitation method. The cytotoxicity of the surface modified CdSe QDs was evaluated in HepG2 cell model with MTT viability assay. The results showed that the cytotoxicity of the surface modified CdSe QDs in vitro was dependent on the surface properties. Surface modification with F-68 and SDS could lessen the cytotoxicity of CdSe QDs, while surface modification with CTAB showed significant cell damage. CdSe QDs surface modified with F-68 were injected into mice and the fluorescence images in viscus were obtained. The results suggested that CdSe QDs surface modified with F-68 have low cytotoxicity and good potential for biological labeling and imaging applications.