PREPARATION AND CELL COMPATIBILITY OF FUNCTIONALIZED BIODEGRADABLE POLY(DL-LACTIDE-co-RS-β-MALIC ACID)

In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL- lactide-co-RS-β-benzyl malolactonate)(PDLLMA),which was from the ring-opening polymerization of DL-lactide(DLLA) and RS-β-benzyl malolactonate(MA)using stannous octoate as catalyst.The copolymers were characterized by ~1H-NMR, FTIR,GPC and DSC.The tensile strength and water uptake of the copoly...

聚乳酸改性糯玉米淀粉的制备及表征

以糯玉米淀粉为原料、异辛酸亚锡为催化剂,在丙交酯熔融体系中制备了聚乳酸改性糯玉米淀粉。建立了聚乳酸改性糯玉米淀粉取代度的^(1)HNMR测试方法,以取代度为响应值,反应时间、反应温度、丙交酯添加量为考察因素,通过单因素和响应面实验优化了聚乳酸改性糯玉米淀粉的合成工艺,得到最优工艺为:反应时间12.46 h,反应温度111.75℃,丙交酯添加量为淀粉质量的258%,预测最大取代度为0.0253,通过实际操作条件调整后实际取代度为0.0238。对最优条件下制备的聚乳酸改性淀粉进行了系列表征,证实聚乳酸改性糯玉米淀粉的颗粒结构没有被完全破坏,晶型、相对分子质量等性能优于溶剂法传统技术制备的聚乳酸改性糯玉米淀粉。

Lightweight,Strong and High Heat-Resistant Poly(lactide acid)Foams via Microcellular Injection Molding with Self-Assembly Nucleating Agent

Poly(lactide acid)(PLA)foams have shown considerable promise as eco-friendly alternatives to nondegradable plastic foams,such as polystyrene(PS)foams.Nevertheless,PLA foam typically suffers from low heat-resistance and poor cellular structure stemming from its inherent slow crystallization rate and low melt strength.In this study,a high-performance PLA foam with well-defined cell morphology,exceptional strength and enhanced heat-resistance was successfully fabricated via a core-back microcellular injection molding(MIM)process.Differential scanning calorimetry(DSC)results revealed that the added hydrazine-based nucleating agent(HNA)significantly increased the crystallization temperature and accelerated the crystallization process of PLA.Remarkably,the addition of a 1.5 wt%of HNA led to a significant reduction in PLA’s cell size,from 43.5µm to 2.87µm,and a remarkable increase in cell density,from 1.08×10^(7)cells/cm^(3)to 2.15×10^(10)cells/cm^(3).This enhancement resulted in a final crystallinity of approximately 55.7%for the PLA blend foam,a marked improvement compared to the pure PLA foam.Furthermore,at 1.5 wt%HNA concentration,the tensile strength and tensile toughness of PLA blend foams demonstrated remarkable improvements of 136%and 463%,respectively.Additionally,the Vicat softening temperature of PLA blend foam increased significantly to 134.8°C,whereas the pure PLA foam exhibited only about 59.7℃.These findings underscore the potential for the preparation of lightweight injection-molded PLA foam with enhanced toughness and heat-resistance,which offers a viable approach for the production of high-performance PLA foams suitable for large-scale applications.

开环聚合法合成聚乳酸

以乳酸为原料、异辛酸亚锡为催化剂自制丙交酯,通过丙交酯开环聚合法合成高熔点聚乳酸。研究了催化剂含量对丙交酯的收率影响,反应时间对聚乳酸热性能的影响。运用FTIR、DSC、TG分析方法对合成得的丙交酯和聚乳酸进行了性能表征。采用体积比为4%的异辛酸亚锡为催化剂,乳酸于170℃反应聚合生成低聚乳酸,然后,升温至240℃解聚蒸出丙交酯,其收率可达79.5%。丙交酯经重结晶后熔融温度升高,熔程变窄。自制丙交酯在130℃油浴、真空条件下分别反应4、6、8 h,可制得聚乳酸,其熔融温度分别为160、162和165℃,热失重温度分别为288、292和296℃,呈现逐渐升高的趋势。

P(LA-TMC)共聚物对聚乳酸增韧性能的研究

聚乳酸(PLA)是一类生物可降解高分子材料,但在实际应用中存在质脆、耐高温性能差等缺点。生物可降解聚合物增韧PLA是未来研究的重点和趋势。以丙交酯(L-LA)和三亚甲基碳酸酯(TMC)作为反应原料,辛酸亚锡(Sn(Oct)2)为催化剂,合成P(LA-TMC)共聚物后,再与PLA共混制备成薄膜。通过核磁共振氢谱、凝胶渗透色谱仪、差示扫描量热仪、广角X射线衍射、热重测试、力学性能等表征手段,探究了P(LA-TMC)对PLA增韧性能的影响。结果表明,P(LA-TMC)共聚物可以增韧PLA。P(LA-TMC)的数均分子质量为70715 g/mol;随着P(LA-TMC)含量的增大,改性薄膜P(LA-TMC)/PLA的玻璃化转变温度和拉伸强度逐渐降低,热稳定性和断裂伸长率逐渐增大;PLA薄膜的衍射峰越来越显著。

Preparation and characterization of poly(D,L-lactide) and its porous biomaterials

Poly(D,L-lactide) was synthesized by indirect method from D,L-lactic acid and characterized by infrared spectrum and proton nuclear magnetic resonance. The influences of monomer purity, initiator concentration, polymerization temperature and polymerization time on the relative molecular mass of poly(D, L-lactide) were investigated. The polylactide was made into porous materials by using solvent-casting particulate-leaching method. Under the optimized conditions, polylactides with a viscosity average molecular mass up to 1.82×105 are obtained and the results are fairly reproducible. Scanning electron microscope observation indicates that the sample is highly porous and well-distributed with good interconnections between pores and the pore size of porous materials is in the range from 200 μm to 500 μm and it can be used as scaffold for bone tissue engineering.

Synthesis of optically active lactide catalyzed by nanocrystals of La-Ti composite oxides

With sol-gel method,nanometer La-Ti composite oxides were prepared.By means of atomic force microscope,the surface pattern,particle size distribution and specific surface area were studied.The newly prepared nanocrystals of La-Ti composite oxides were used as the catalysts to catalyze the dehydration of external compensated lactic acid to lactide.The lactide product was measured by polarimeter and micropolariscope.The results demonstrate that the ratio between D-lactide and L-lactide will not be equal to 1-1 if nanocrystals of La-Ti composite oxides are used as the catalysts,which implies,that nanocrystals of La-Ti composite oxides may be potential catalysts with a good selectivity.

Development of a fast and precise method for simultaneous quantification of the PLGA monomers lactic and glycolic acid by HPLC

Poly(lactide-co-glycolide acid)(PLGA) is an extraordinary well-described polymer and has excellent pharmaceutical properties like high biocompatibility and good biodegradability. Hence, it is one of the most used materials for drug delivery and biomedical systems, also being present in several US Food and Drug Administration-approved carrier systems and therapeutic devices. For both applications, the quantification of the polymer is inalienable. During the development of a production process, parameters like yield or loading efficacy are essential to be determined. Although PLGA is a well-defined biomaterial,it still lacks a sensitive and convenient quantification approach for PLGA-based systems. Thus, we present a novel method for the fast and precise quantification of PLGA by RP-HPLC. The polymer is hydrolyzed into its monomers, glycolic acid and lactic acid. Afterwards, the monomers are derivatized with the absorption-enhancing molecule 2,4′-dibromoacetophenone. Furthermore, the wavelength of the derivatized monomers is shifted to higher wavelengths, where the used solvents show a lower absorption,increasing the sensitivity and detectability. The developed method has a detection limit of 0.1 mg/mL,enabling the quantification of low amounts of PLGA. By quantifying both monomers separately, information about the PLGA monomer ratio can be also directly obtained, being relevant for degradation behavior. Compared to existing approaches, like gravimetric or nuclear magnetic resonance measurements, which are tedious or expensive, the developed method is fast, ideal for routine screening, and it is selective since no stabilizer or excipient is interfering. Due to the high sensitivity and rapidity of the method, it is suitable for both laboratory and industrial uses.

Synthesis and Hydrophilic Performance of Poly(Lactic Acid)-Poly(Ethylene Glycol) Block Copolymers

Lactide was synthesized using lactic acid and stannous octoate as raw material and catalyst, respectively. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was prepared by lactide and poly (ethylene glycol) (PEG) via ring-opening polymerization. The most appropriate technological conditions of synthesis of lactide were researched in the paper. The copolymers were measured by Infrared spectroscopy (IR) and 1H nuclear magnetic resonance (1H NMR). The results proved that the lactide and PLA-PEG were synthesized successfully. Hydrophilic performance of the copolymer was measured by a water contact angle tester after prepared into a flat membrane. The water contact angle changed from 81.5? to 71.6?, which proved that the hydrophily of PLA-PEG was better than PLA.

Transplantation of Nogo-66 receptor gene-silenced cells in a poly(D,L-lactic-co-glycolic acid) scaffold for the treatment of spinal cord injury

Inhibition of neurite growth, which is in large part mediated by the Nogo-66 receptor, affects neural regeneration following bone marrow mesenchymal stem cell transplantation. The tissue engineering scaffold poly（D,L-lactide-co-glycolic acid） has good histocompatibility and can promote the growth of regenerating nerve fibers. The present study used small interfering RNA to silence Nogo-66 receptor gene expression in bone marrow mesenchymal stem cells and Schwann cells, which were subsequently transplanted with poly（D,L-lactide-co-glycolic acid） into the spinal cord lesion regions in rats. Simultaneously, rats treated with scaffold only were taken as the control group. Hematoxylin-eosin staining and immunohistochemistry revealed that at 4 weeks after transplantation, rats had good motor function of the hind limb after treatment with Nogo-66 receptor gene-silenced ceils prus the poly（O,L-lactide-co-glycolic acid） scaffold compared with rats treated with scaffold only, and the number of bone marrow mesenchymal stem cells and neuron-like cells was also increased. At 8 weeks after transplantation, horseradish peroxidase tracing and transmission electron microscopy showed a large number of unmyelinated and myelinated nerve fibers, as well as intact regenerating axonal myelin sheath following spinal cord hemisection injury. These experimental findings indicate that transplantation of Nogo-66 receptor gene-silenced bone marrow mesenchymal stem cells and Schwann cells plus a poly（D,L-lactide-co-glycolic acid） scaffold can significantly enhance axonal regeneration of spinal cord neurons and improve motor function of the extremities in rats following spinal cord injury.

Preparation and biocompatibility evaluation of poly(D,L-lactide-co-glycine)

D,L-lactide was prepared from D,L-lactic acid by means of polymerization and depolymerization at low vacuum level.Morpholine-2,5-dione(MD) was synthesized from the cyclization of chloroacetyl glycine which was made from chloroacetyl chloride and glycine in the basic condition.A novel copolymer(PLAMD) with D,L-lactide(D,L-LA) and morpholine-2,5-dione(MD) was synthesized using stannous octoate as initiator,and characterized with FT-IR and 1HNMR.The biocompatibility of PLAMD and PLA was investigated by MTT and microscope.The results show that amino acid is introduced into PDLLA main chain.PLAMD has better cell affinity than PLA,so it is a promising biomaterial.

一步法合成丙交酯

聚乳酸(PLA)是最有前途的可生物降解聚合物之一。国家“禁塑令”的颁布,使得PLA产量和应用领域得到史无前例的扩大。丙交酯(LD)作为生物塑料PLA的关键中间体,其化学纯度、光学纯度和生产成本直接决定PLA的质量和经济价值。目前工业上常见的是两步法合成技术,预聚‒解聚的方法可保证乳酸的转化率,但是难以避免LD外消旋化反应,选择性低,能源成本高。一步法作为一种替代策略,很好地克服了两步法合成LD的一些缺点。因此,文中重点介绍一步法合成LD,并对不同的方法进行了介绍和技术比较。

L-乳酸合成L-丙交酯过程中的定量问题及其提高选择性的方法

聚乳酸(PLA)是一种很有前途的可降解、可再生和生物相容性的聚合物,L-丙交酯作为生产聚乳酸的重要中间体,其纯度直接影响聚乳酸的质量和生产成本。丙交酯通常采用气相色谱法(GC)、液相色谱法(LC)或核磁共振氢谱法(^(1)H NMR)定量。然而,发现GC在乳酸生产丙交酯的过程中并不适用于定量,丙交酯收率总是比LC高得多。详细的分析表明,一些在反应过程中没有完全转化的乳酸低聚物在高温下可以发生解聚生成丙交酯,从而使丙交酯的产率比实际的高。因此,LC是一种较为准确的丙交酯定量分析方法。基于这一现象,采用固定床反应器模拟GC分析的反应条件,大大提高了丙交酯的选择性和收率。优化后的反应条件可使丙交酯的最高收率达到100%。

Synthesis of L-Aspartic Acid and Lactone Copolymers

Biodegradable poly(alc-alt-Asp) was synthesized by ring-opening polymerization of the monomer 3-(S)-[(benzyloxycarbonyl)methyl] -morpholine-2, 5-dione and subsequent catalytic hydrogenation. Copolymers of the monomer with glycolide, D,L-lactide and L-lactide were also prepared.

透明质酸功能修饰聚乳酸取向超细纤维促进血管平滑肌细胞的迁移

基于稳定射流同轴电纺丝法(SJCES),选用透明质酸(HA)对电纺左旋聚乳酸(PLLA)取向超细纤维进行表面功能修饰得到壳-芯结构的取向纤维(HA-PLLA),以提高血管平滑肌细胞(vSMCs)在纤维表面的黏附和迁移能力。首先在无血清饥饿处理条件下观察HA促进vSMCs迁移的功效;然后采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、红外光谱仪(FT-IR)、X-射线衍射仪(XRD)和万能材料测试仪等对纤维形貌、壳-芯结构和力学性能进行表征;最后通过改良版“伤口”愈合实验检测HA-PLLA取向纤维诱导vSMCs迁移的功效。结果表明:HA具有显著促进vSMCs迁移的作用;SJCES法可成功制备HA-PLLA壳-芯取向纤维;HA修饰可显著提高PLLA取向纤维的细胞相容性,并增强其定向引导vSMCs迁移的能力,从而证实了HAPLLA取向纤维促进vSMCs迁移的有效性。

共沸反应精馏合成丙交酯的工艺研究

提出了一种共沸反应精馏合成丙交酯的工艺。首先,对共沸反应精馏合成丙交酯进行了实验研究,然后运用Aspen Plus软件对工艺进行流程模拟和优化设计,并得出优化后的各操作参数。结果表明,在共沸精馏下反应,丙交酯产率为82.64%,纯度为98%。采用Aspen软件模拟确定最佳优化的条件为:理论板数15、回流比5、进料位置为第8块塔板、精馏段和提馏段的塔板数分别为4和5,此时,丙交酯产率达到86.48%。实验结果与工艺设计优化结果吻合度较高,为进一步的工业化奠定基础。

高产率、高光纯丙交酯生产工艺和装备突破

丙交酯是生产可降解生物材料聚乳酸的核心聚合单体,高品质的丙交酯对于生产性能优异、可替代石油基塑料制品的高端聚乳酸产品十分关键。然而,丙交酯产业化生产目前存在产率低、光纯度差的技术瓶颈,相关研究机构和生产企业为了提高丙交酯的综合产率和光学纯度做了很多努力,但现有技术无法处理好产率、光纯度以及生产成本三者之间的平衡。从化学反应理论和工业装备方面剖析了现有丙交酯生产技术存在的瓶颈,开发出高产率、高光纯丙交酯产业化生产工艺路线,并阐述了新工艺路线设计的理论依据和取得的实际效果。相关专利技术已经获得授权,为实现从理论到产业层面全方位突破国外对高品质丙交酯产品的技术垄断奠定了基础。

D,L-丙交酯的合成与纯化

以D,L-乳酸为原料,在催化剂存在下通过脱水环化合成D,L-丙交酯,研究了反应过程中催化剂用量、脱水温度及稀释剂等因素对D,L-丙交酯产率的影响。用重结晶法对粗产物进行纯化,制备出高产率、高纯度的D,L-丙交酯。实验结果表明,采用二丁基氧化锡为催化剂,最佳催化剂用量(质量分数)为1 5%,最佳脱水温度为140℃,且在反应中加入稀释剂可以显著提高D,L-丙交酯的粗产率;乙醇是理想的重结晶溶剂,粗产物经多次纯化后,可获得总产率达37 3%的纯D,L-丙交酯。

L-丙交酯和聚L-乳酸的制备与性能

从左旋 L-乳酸经高温催化反应得到低聚 L-乳酸 ,再经高温裂解减压蒸馏制得单体 L-丙交酯( LL A) ,理论收率高达 80 %以上。LL A经纯化 ,再以辛酸亚锡为催化剂开环聚合得到聚 L-丙交酯 (聚 L-乳酸 ,PLLA) ,其粘均分子量可达到 4 0万。

高效液相色谱法测定乳酸菌中的γ-氨基丁酸

建立了邻苯二甲醛柱前衍生高效液相色谱法。定量测定短乳杆菌中γ-氨基丁酸的方法,为进一步研究乳酸菌中的γ-氨基丁酸奠定了方法基础。在对浓缩发酵上清液柱前衍生后,利用Nova2pakC18色谱柱,以50mmol/L的乙酸钠(pH6.8)-甲醇-四氢呋喃(A相,82:17:1;B相,22:77:1,V/V)为流动相进行梯度洗脱,可以检测到痕量γ-氨基丁酸(2.2mg/100g)。精确度和回收率实验表明,该方法可以用于痕量γ-氨基丁酸的检测。