O,O-双十二酰化壳寡糖的溶解性能及固态结构

采用甲烷磺酸保护壳寡糖的氨基,通过月桂酰氯与壳寡糖的羟基反应合成了O,O-双十二酰化壳寡糖。差示扫描量热(DSC)分析和热重分析(TGA)表明,随着月桂酰氯与壳寡糖的摩尔比增加,O,O-双十二酰化壳寡糖的DSC曲线出现了月桂酰基侧链的熔融峰,而且O,O-双十二酰化壳寡糖的热稳定性均低于壳寡糖。扫描电镜(SEM)及X射线衍射(XRD)分析表明,酰化反应改变了原壳寡糖的结晶结构,并且月桂酰基侧链能够形成新的结晶微区。溶解性实验结果表明,所有酰化壳寡糖在氯仿、吡啶、四氢呋喃中的溶解性得到改善。     

O,O-双十二酰基壳聚糖/聚乳酸复合膜中氢键的作用

研究了氢键对O,O-双十二酰基壳聚糖/聚乳酸(OCS/PLLA)溶液复合膜相容性的影响.结果表明,复合膜中氨基和羟基的伸缩振动谱带相对各纯组分均有明显的红移,OCS的氨基与PLLA的羰基之间存在强烈的氢键作用;随着OCS含量的增加,PLLA在2θ=16.7°和2θ=19.1°的结晶衍射峰往低角度略有偏移,峰强逐渐减弱;当OCS含量(质量分数)≥60%时,PLLA的结晶衍射峰甚至消失,表明氢键使OCS分子链插层到PLLA的晶格中,溶液法制备的复合膜具有良好的相容性;低于100℃升温可使OCS与PLLA之间的氢键加强,热处理有利于改善复合膜的相容性.     

PCL/PLLA共混体系的微相分离结构调控及力学性能和气体水蒸气阻隔性能

采用熔融共混法制备了不同聚乳酸(PLLA)组分的聚己内酯/聚乳酸(PCL/PLLA)非均相共混薄膜,研究了其力学性能、气体和水蒸气阻隔性能,并探讨了共混物相结构与各阻隔性能之间的关系。结果表明,不同PLLA共混比例的PCL/PLLA共混膜形成了具有不同相分离结构的非均相体系。当PLLA共混比例高于50%时,共混薄膜体系的相分离结构和相容性得到改善,共混膜的拉伸强度和弹性模量大幅度增加,同时保持了较高的断裂伸长率,而气体和水蒸气透过性却明显降低。相比于纯PCL,PCL/PLLA(75)共混膜的拉伸强度和弹性模量分别达到68.1 MPa和1136.4 MPa,较PCL分别增加了166%和289%;5℃时,PCL/PLLA(75)共混膜的O_2和CO_2透过系数分别降低了70%和87%;此外,在室温条件下,PCL/PLLA(75)共混膜的水蒸气透过系数降低了31%。     

聚乳酸/明胶共混膜的固体核磁共振研究

以DMSO作为聚乳酸(PLLA)和明胶的共溶剂,采用浇铸法将PLLA与明胶混合在一起。X射线衍射结果表明PLLA用DMSO溶解后,在重新干燥的过程中,PLLA的堆积结构会发生变化,半结晶态的PLLA变成无定形态。使用固体^13C CP／MAS NMR测定了原料PLLA以及不同比例的PLLA／明胶共混膜的弛豫时间,发现PLLA100及所有共混膜的弛豫时间与原料PLLA相比,显著增加,分子运动加剧。进一步证明了PLLA在用DMSO处理后由半晶态转变成了无定形态,明胶的加入,不影响聚乳酸的结晶结构。     

立构复合结构增韧左旋聚乳酸的结构与性能

以左旋聚乳酸(PLLA)为基体聚合物材料、右旋聚乳酸-聚乙二醇-右旋聚乳酸(PDLA-PEG-PDLA)三嵌段共聚物作为增韧改性剂,通过熔融共混方法制备了PLLA/PDLA-PEG-PDLA共混物。通过红外光谱(FT-IR)、差示扫描量热仪(DSC)、X射线衍射(XRD)和拉伸行为测试对PLLA和PLLA/PDLA-PEG-PDLA共混物的结构、晶型和力学性能进行了研究。结果表明,PDLA-PEG-PDLA三嵌段共聚物的加入,共混体系生成了PLA立构复合结构。与纯PLLA相比,PLLA共混物的玻璃化转变温度显著下降,热稳定性能明显改善,而且PLLA基体的韧性得到了较大程度的提高。     

钛酸钾晶须/L型聚乳酸共混物的热稳定性及力学性能研究

采用1%～5%不同浓度的碳酸钾晶须(PTW)对精制后的L型聚乳酸(PLLA)进行共混改性,以三氯甲烷为溶剂制成膜。分别用调制式热重分析法(MTGA),红外光谱(FTIR-ATR)和动态力学分析(DMA)对其进行表征。MT-GA结果表明PTW/PLLA共混物热分解的活化能Ea、指前因子Z和比速率ln[rate ratio]等热分解动力学常数均较未添加晶须的PLLA高,且PLLA的热分解过程为一步反应,FTIR-ATR和DMA结果表明,和PLLA相比,PTW/PLLA共混物的力学性能均有所改善。     

聚乳酸/明胶共混膜的形态和结构

采用二甲基亚砜(DMS0)作为共溶剂将两种不同的生物高分子L-聚乳酸(PLLA)和明胶混合在一起，扫描电镜(SEM)研究结果表明两种组分共混时存在着明显的相分离。当明胶含量在5%以下时，明胶为分散相，明胶粒子在共混膜中的尺寸为几百纳米。PLLA用DMSO溶解后，在重新干燥的过程中，PLLA的堆积结构会发生变化，它的玻璃化转变温度由56℃变为38℃。共混膜中混入的明胶含量在5％以内时，在保持聚乳酸力学性能的同时，可以降低聚乳酸的接触角，改善聚乳酸的亲水性。     

电纺PLLA/PCL/PEG共混纤维膜的结构及性能

采用静电纺丝技术制备了聚乳酸（PLLA）/聚己内酯（PCL）/聚乙二醇（PEG）共混纤维膜,考察了溶剂体积比、共混物共混质量比、溶液浓度对电纺纤维形貌的影响,研究了共混纤维膜的热稳定性、结晶性、力学性能及亲水性。结果表明加入PEG有效提高了共混纤维膜的热稳定性和结晶性,提高了共混纤维膜的拉伸强度、弹性模量和亲水性能。     

左旋聚乳酸/右旋聚乳酸立构复合晶体形状记忆聚合物的制备与性能

通过环保高效的熔融共混在左旋聚乳酸(PLLA)中引入少量的右旋聚乳酸(PDLA),使得聚乳酸立构复合晶体(sc-PLA)在PLLA基体中原位形成并均匀分散,制备得到全生物可降解的聚乳酸形状记忆聚合物(SMPs)功能材料。当仅向PLLA基体中加入1%PDLA时,就可使得sc-PLA晶体在PLLA中原位形成,且随着PDLA含量的不断增加,sc-PLA晶体的含量也不断增加。动态力学测试结果表明,sc-PLA晶体几乎不影响PLLA/PDLA共混材料的玻璃化转变温度,却可提高PLLA的高温段模量。形状记忆性能测试表明,PLLA和PLLA/PDLA共混材料均具有极佳的形状固定率(R_f≈100%),而PLLA/PDLA共混材料形状回复率R_r随着PDLA含量的增加呈现先增加后下降的趋势。当PDLA质量分数为3%时,PLLA/PDLA共混材料的形状记忆回复率(R_r)达到最佳(R_r≈85.31%),且进一步的测试表明PLLA/3PDLA共混材料的形状记忆性能在多次同等条件重复测试后仍能持续保持。     

聚乳酸/聚乙烯醇共混膜的制备

基于流延法和溶剂蒸发技术,以聚乳酸(PLA)和聚乙烯醇(PVA)为原料,制备可降解PLA/PVA共混膜。通过考察不同的共溶剂对共混膜成膜性能的影响,确定二甲基亚砜(DM SO)是制备PLA/PVA共混膜优良的共溶剂。研究PLA与PVA配比对PLA/PVA共混膜性能的影响,探索PLA与PVA分子链在共混膜中的结合状况。结果表明,当PLA的含量低于20%时,可以得到均质的PLA/PVA共混膜,且PLA与PVA分子链间以氢键结合。此外,在共混过程中,PLA与PVA的结晶均受到一定的破坏,结晶度比纯PLA与PVA下降。     

Morphology and adhesion of mesenchymal stem cells on PLLA,apatite and apatite/collagen surfaces

Biomimetic apatite/collagen composite coating, previously reported particularly with regard to its fabrication, characterization and interaction with osteoblast-like cells, has been investigated in this study to understand the response of human mesenchymal stem cells (hMSC) to such surface. PLLA films and PLLA films with apatite coating were compared with PLLA films with apatite/collagen composite coating. The hMSC morphology in response to such conditions was first observed using fluorescence microscopy. To further understand such cell-material interactions at a molecular level, integrin expression, actin assembly and vinculin-positive focal adhesion plaques were examined. Our results demonstrated that spreading of stem cells on the apatite/collagen composite surface was determined best among the three types of surfaces, followed by the apatite surface and then the PLLA control. Integrin expression on the apatite/collagen surface was higher than those on the apatite surface and PLLA surface. Immunostaining for vinculin and actin suggested that the composite coating on PLLA enhanced the formation of focal adhesion.     

Osteointegration of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)PLLA and poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)PLLA/poly(ethylene oxide)PEO implants in rat tibiae

Natural or synthetic materials may be used to aid tissue repair of fracture or pathologies where there has been a loss of bone mass. Polymeric materials have been widely studied, aiming at their use in orthopaedics and aesthetic plastic surgery. Polymeric biodegradable blends formed from two or more kinds of polymers could present faster degradation rate than homopolymers. The purpose of this work was to compare the biological response of two biomaterials: poly(L: -lactic acid)PLLA and poly(L: -lactic acid)PLLA/poly(ethylene oxide)PEO blend. Forty four-week-old rats were divided into two groups of 20 animals, of which one group received PLLA and the other PLLA/PEO implants. In each of the animals, one of the biomaterials was implanted in the proximal epiphysis of the right tibia. Each group was divided into subgroups of 5 animals, and sacrificed 2, 4, 8 and 16 weeks after surgery, respectively. Samples were then processed for analysis by light microscopy. Newly formed bone was found around both PLLA and PLLA/PEO implants. PLLA/PEO blends had a porous morphology after immersion in a buffer solution and in vivo implantation. The proportion 50/50 PLLA/PEO blend was adequate to promote this porous morphology, which resulted in gradual bone tissue growth into the implant.     

柞蚕丝素/壳聚糖共混膜的结构及细胞相容性

用碳化二亚胺(EDC)作为交联剂,流延法制备柞蚕丝素(ASF)/壳聚糖(CS)共混膜。用扫描电镜(SEM)、红外光谱(FT-IR)、热重分析(TG)和四甲基偶氮唑盐比色法(MTT)对膜的结构及细胞相容性进行了研究。结果显示,柞蚕丝素和壳聚糖具有较好的相容性和较强的相互作用,壳聚糖能阻碍共混膜内的丝素蛋白形成β-折叠构象。EDC能分别与柞蚕丝素及壳聚糖反应,从而对共混膜进行有效的交联,并使膜的热稳定性提高。与ASF膜或CS膜相比,共混比为80/20和40/60的ASF/CS共混膜更有利于细胞生长和增殖,作为一种新型的生物材料具有良好的研究和开发应用前景。     

Electrospun poly(l-lactide)/zein nanofiber mats loaded with <Emphasis Type="Italic">Rana chensinensis</Emphasis> skin peptides for wound dressing

Electrospun nanofiber mats can display impressive performance as an ideal wound dressing. In this study, poly(l-lactide)(PLLA)/zein nanofiber mats loaded with Rana chensinensis skin peptides (RCSPs) were successfully produced by two different electrospinning techniques, blend and coaxial, with the goal of developing a wound dressing material. The nanofiber mats were investigated by environmental scanning electron microscope (ESEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), water contact angle, mechanical tests and cell viability. The resulting nanofiber mats exhibited smooth surfaces, tiny diameters and different cross-sectional shapes from pure PLLA and zein nanofibers. The FTIR result showed that PLLA, zein and RCSPs were well dispersed, without chemical interactions. Compared with coaxial nanofiber mats, blending zein-RCSPs with PLLA enhanced hydrophilicity but decreased mechanical properties. Adding RCSPs into the electrospun nanofibers significantly improved the mechanical properties of the mats. Cell viability studies with human foreskin fibroblasts demonstrated that cell growth on PLLA/zein-RCSPs nanofiber mats was significantly higher than that on PLLA/zein nanofiber mats. The results indicate that nanofiber mats containing RCSPs are potential candidates for wound dressing.     

Improvement of cytocompatibility of electrospinning PLLA microfibers by blending PVP

In this study, microfiber films were used as scaffolds for the purpose of vascular tissue engineering. The microfiber films were prepared by electrospinning of poly (l-lactide) (PLLA) and polyvinyl pyrrolidone (PVP). PLLA and PVP with different ratios were blended with dichloromethane as a spinning solvent at room temperature. The properties of the composite microfiber films were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and contact angle measurement. The SEM images showed that the morphology of the microfiber films was mainly affected by the weight ratios of PLLA/PVP. The DSC results demonstrated that PLLA and PVP mixed uniformly. And the hydrophilicity of the films measured increased along with the decrease of the PLLA/PVP ratio. Vascular smooth muscle cells (VSMCs) were used to test the cytocompatibility. Cell morphology and cell proliferation were measured by SEM, laser scanning confocal microscopy (LSCM) and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay after 2, 4, 6 days of culture. The results indicated that the cell morphology and proliferation on the composite films were better than that on the pure PLLA film. Furthermore, morphology and proliferation of VSMCs became better with decreasing of the weight ratio of PLLA/PVP. In addition, adhesion of platelet on the films was observed by SEM. The SEM images showed that the number of adhered platelets decreased with increment of PVP content in the films. The electrospinning microfiber composite films of PLLA and PVP would have potential use as the scaffolds for vascular tissue engineering.     

透明耐热聚乳酸共混材料的制备与性能研究

采用熔融共混法制备聚乳酸(PLLA)/聚甲基丙烯酸甲酯(PMMA)透明共混材料.DSC测试结果表明,共混材料只出现一个玻璃化转变温度,说明PLLA/PMMA共混材料在宏观上不发生相分离.力学性能研究发现,PLLA/PMMA共混材料的弯曲强度、抗冲击强度和拉伸强度均优于纯PLLA及纯PM-MA.Avrami指数表明,PM...     

聚乳酸单轴拉伸膜的包装特性研究

目的研究了不同拉伸比的PLLA薄膜的热学性能、阻隔性能和热收缩性能。方法采用双螺杆挤流延试验机单轴拉伸制备了不同拉伸比的PLLA热收缩膜和定向拉伸膜,采用差示扫描量热分析仪(DSC)、透湿仪和透氧仪对不同拉伸比的PLLA薄膜的热学性能和阻隔性能进行了评估,并对PLLA膜的热收缩性进行了测定。结果热收缩膜的拉伸比由1增大到6.5时,PLLA的结晶度由0.2%增加到41.8%,结晶速率明显提高,阻隔性得到了一定的改善。随着拉伸比例的增大,热收缩率随之增大。定向拉伸膜的结晶度得到了大幅度提高,其阻隔性也得到了改善,但不呈现热收缩性。结论通过单轴拉伸可以有效地提高PLLA薄膜的结晶速率和结晶度,经过中等拉伸比例的PLLA薄膜,其阻湿阻氧能力相对较强。     

介孔纳米羟基磷灰石/左旋聚乳酸复合材料的制备及性能

为考察介孔纳米羟基磷灰石(MHA)/左旋聚乳酸(PLLA)复合材料的性能,以十六烷基三甲基溴化铵(CTAB)为模板合成MHA,采用溶液相分离结合粒子沥滤法制备了不同纳米粒子含量的MHA/PLLA多孔支架复合材料,考察了其抗压缩性能和淬断面微观结构。采用溶液浇注法制备了MHA/PLLA复合膜,并对其拉伸性能和拉伸断面微观结构进行了研究。FTIR、XRD、TEM和氮气吸附测试等结果显示:合成的MHA具有典型的晶体结构、介孔结构和较高的比表面积。力学测试结果显示:在发生10%压缩形变时,填料含量为1%、5%和10%的MHA/PLLA多孔支架复合材料的抗压缩强度随填料含量增加而提高,与相应含量的纳米羟基磷灰石(HA)/PLLA多孔支架复合材料相比,分别提高了约37.0%、67.7%和144.7%。在填料含量为5%和10%时,MHA/PLLA复合膜的拉伸强度较HA/PLLA复合膜分别提高约38.7%和46.1%,拉伸模量分别提高约35.4%和14.5%。而且MHA/PLLA复合膜具有更高的断裂伸长率,填料含量为1%、5%和10%时断裂伸长率分别较HA/PLLA复合膜提高约91.3%、79.7%和96.1%。FESEM结果显示:尤其当填料含量较高时,MHA/PLLA多孔支架复合材料或复合膜中填料粒子分布较HA/PLLA中均匀。结果表明:与HA/PLLA复合材料相比,随着MHA含量增加,MHA/PLLA复合材料具有更好的力学性能,MHA在PLLA基体中分布相对更均匀。     

In vitro behavior of osteoblast-like cells on PLLA films with a biomimetic apatite or apatite/collagen composite coating

To investigate the methods to improve the cell–material interaction of devices or tissue engineering scaffolds made of poly(l-lactic acid) (PLLA) polymer, apatite and apatite/collagen composite coatings were formed on PLLA films within 24 h through accelerated biomimetic processes. In vitro investigation using Saos-2 osteoblast-like cells through cell culture was conducted to assess the biological performance of these biomimetic coatings. The cell morphology on three types of surfaces, viz., PLLA film, PLLA film with the apatite coating, and PLLA film with the apatite/collagen composite coating, was studied using scanning electron microscopy (SEM). Cell viability was estimated using the MTT assay. The differentiated cell function was assessed by measuring the alkaline phosphatase (ALP) activity. The results obtained indicated that the biomimetic apatite and apatite/collagen composite coatings could significantly enhance the proliferation and differentiation of osteoblast-like cells. The apatite/collagen composite coating appears to be promising for the surface modification of PLLA-based devices with much improved interactions with osteoblastic cells.