聚乳酸材料的仿生修饰研究进展

聚乳酸是生物可降解、生物相容性材料,但由于存在亲水性差、缺乏细胞识别位点等缺陷,限制了其在生物医学工程中的应用.模拟细胞与基质相互作用的特点以及细胞外基质的特性,通过表面修饰、本体改性和复合加工的方法在聚乳酸中引入蛋白胶原、活性肽、多糖以及羟基磷灰石等生物活性分子,实现聚乳酸的仿生修饰,能够有效提高聚乳酸材料的生物学功能.综述了利用这些生物活性分子对聚乳酸进行仿生修饰的研究进展.     

高分子专利EI

本发明提供了一种采用马来酸酐改性的聚乳酸和生物活性物质为原料,制备生物活性聚乳酸材料的方法及其产物和应用,方法步骤：①直接加入有机二胺或二醇或羟胺或水进行反应;②产物经分离纯化后,在有机交联剂的作用下,加入聚乙二醇（也称聚环氧乙烷）或其衍生物反应;然后,③产物经分离纯化后,在有机交联剂的作用下,再加入生物活性物质反应,或在步骤②在有机交联剂的作用下,直接加入生物活性物质反应,获得生物活性聚乳酸产物。采用本方法,通过改变生物活性物质的种类,可制备具有不同生物活性的聚乳酸材料;也可通过本方法,选择一些药物为反应原料制备高分子药物。这种生物活性聚乳酸可很好地用作组织工程支架、药物靶向缓释载体等。     

钛及钛合金仿生表面改性研究进展

钛及钛合金具有较好的生物相容性及优良的机械性能，在临床上得到了越来越广泛的应用。表面生物活性化能够进一步改善其表面性能，提高表面生物活性。本文对钛及其合金的仿生表面改性进行了综述，具体介绍了化学法、促形核剂法、自组装单分子法的活化机理，并对仿生表面改性的发展方向进行了探讨。     

几种聚乳酸／生物活性陶瓷复合材料生物活性的比较

采用溶解共混法制备含30％硅灰石的聚乳酸／硅灰石新型生物医用复合物膜．将其放入37．5℃模拟体液中,分别在1,3和6d取出样品,从沉积物形成速度以及沉积物的量考察复合物的生物活性,并与目前研究应用较多的聚乳酸／羟基磷灰石、聚乳酸／磷酸三钙以及聚乳酸／珍珠层粉进行比较。扫描电镜和红外光谱分析表明,聚乳酸／硅灰石、聚乳酸／羟基磷灰石和聚乳酸／磷酸三钙复合物膜的生物活性明显优于聚乳酸／珍珠层粉,这三种复合物膜表面在浸泡一天时表面出现类骨羟基磷灰石沉积物,6d时表面完全被沉积物覆盖。聚乳酸／硅灰石复合物材料具有较好的生物活性,适于应用在骨修复以及骨组织工程领域。     

与血液接触材料表面活化的研究进展

与血液接触材料的表面活化是对材料表面进行改性处理,并粘附生长有利于抗凝血性的蛋白和细胞等,进而发展具有表面生物活性的材料,通过生物识别途径,更好地提高其抗凝血性.从表面结构、抗凝活化层表面、表面内皮细胞化、表面磷脂化等方面概述了与血液接触材料表面活化的近期研究进展.     

浅析纳米氧化锌的制备及应用现状

纳米氧化锌是一种新型多功能无机材料,具有热稳定性和化学稳定性等特性。本文简述了纳米氧化锌的结构与性能,综述了其制备方法:物理法、化学法和综合法,简述了氧化锌的表面改性,对纳米氧化锌的制备与应用研究进行展望。     

聚乳酸分离膜的制备、改性及其应用进展

聚乳酸是一种可持续的绿色环保高分子材料,具有明显的可再生优势,已经被制成各种类型的分离膜,有望在分离和纯化领域替代难降解的高分子膜,既能节约石化资源又能减少白色污染.本文分析了浸没沉淀相转化法、热致相分离法和静电纺丝法制备聚乳酸分离膜的优缺点,评价了聚乳酸膜的4种亲水改性方法,即物理共混、表面偏析、表面接枝和表面生物黏合,总结了聚乳酸被制成微滤膜、超滤膜、电纺微滤膜和致密膜等在分离与纯化领域的应用进展,最后指出聚乳酸分离膜目前存在的问题,并给出下一步改进方向,以期能为今后的相关研究工作与工业应用提供有益的参考.     

聚乳酸复合材料共混改性研究进展

聚乳酸(PLA)具有优异的生物可降解性,且生物相容性好,从而广泛应用于生物医疗、农业和食品包装等领域,但因其性脆、柔韧性差、熔体强度较低,限制了其应用范围的扩展。需通过与其他材料进行物理或化学改性制备复合材料以提高其加工性能和力学性能。综述了近年来共混改性制备聚乳酸复合材料的研究,主要介绍了PLA/合成聚合物、PLA/碳材料、PLA/无机纳米粒子、PLA/笼型倍半硅氧烷、PLA/天然高分子等复合材料的研究进展。     

新型生物活性材料的设计和研究进展

生物活性材料是生物医用材料领域中一个重要的研究方向.研究表明,在体液的作用下这类材料的表面能够形成Si-OH、Ti-OH、Ta-OH、-COOH和PO4H2等功能基团,从而诱导类骨磷灰石层生成并与骨发生键合.综述了人们利用医用金属进行表面生物活化或通过有机/无机复合的方法得到力学性能良好的新型生物活性材料,为人工植入体的临床应用提供了更广阔的前景.     

超临界CO_2诱导相分离法工艺条件对左旋聚乳酸多孔支架孔形貌和结构的优化调控

采用超临界CO_2诱导相分离法制备了左旋聚乳酸多孔支架材料,研究了原料的分子量、超临界CO_2的压力和温度对制备多孔材料的孔结构如孔隙率、大孔孔径及内连通孔径的影响和优化调控。与传统方法所制得的材料相比较,制备的多孔材料杂质少,分布均匀,孔洞表面粗糙,而且在大孔之间布满了直径为5~20μm的微孔。同时通过SEM、FT-IR以及DSC对优化条件制备的产品表面及截面结构、形貌及理化性质进行了系统分析研究。结果表明,制备的支架材料的孔结构和形貌可以通过对左旋聚乳酸原料的分子量、处理样品的压力和温度等工艺参数优化选择来对产品结构进行优化调控而适合不同生物及医学应用需要。     

Improvement of surface bioactivity of poly(lactic acid) biopolymer by sandblasting with hydroxyapatite bioceramic

This study communicates a simple and effective method for modification of the surface of synthetic biopolymer poly(lactic acid) (PLA) with bioactive ceramic hydroxyapatite (HA) using a sandblasting technique. The sandblasting particles were bombarded onto the PLA, covering the surface quite evenly. The HA-sandblasted PLA showed good in vitro apatite forming ability in a simulated body fluid within a few days, which was rarely observed for pure PLA. Moreover, the HA-sandblasted PLA enhanced the initial cell adhesion and further proliferation, and up-regulated bone cell functions such as the alkaline phosphatase activity. This novel method of surface modification of the biopolymer with bioactive ceramic has the potential for use in developing bone bioactive implantable materials.     

In Vitro Stability of Poly(D,L-lactide) and Poly(D,L-lactide)/Poloxamer Nanoparticles in Gastrointestinal Fluids

Abstract

Poty(D,L-lactide) (PLA) nanoparticles of various surface and bulk properties were prepared by a nanoprecipitation procedure and evaluated for their physical and chemical in vitro stability in simulated gastrointestinal fluids of 37°C. The influence of polymer characteristics and poloxamer 188 (POL 188) adsorption was studied. Physical stability was followed by visual appearance, particle size, and zeta potential measurements. Molecular weight changes were analyzed by gel permeation chromatography (GPC). Due to a sharp decrease in their negative zeta potential, poloxamer-free nanoparticles flocculated in simulated gastric fluid, irrespective of the polymer properties. Their physical stability in protein-free intestinal fluids increased with an increase in carboxy end group concentration of the PLA and thus, with an increase in their negative zetapotential. Protein effects at pH 7.5 were rather complex indicating a stabilizing effect of negatively charged proteins and a destabilizing effect of positively charged proteins. Poloxamer 188 adsorption sterically stabilized the nanoparticles against flocculation in gastric fluid, irrespective of the PLA characteristics. Physical stability of the PLA/POL 188 nanoparticles in intestinal fluids was affected by the PLA characteristics. Poloxamer 188 increased the physical stability of nanoparticles composed of hydrophobic PLA, irrespective of the proteins present. A gradual particle size increase could, however, be observed for PLA/POL nanoparticles composed of PLA with a high content of carboxy end groups, especially in combination with positively charged proteins. This effect is most likely due to a decrease in PLA/POL interactions resulting from the ionization of the carboxy end groups located on the nanoparticle surface and leading to conformational changes and/or a distinct desorption of POL 188. The chemical stability of PLA and PLA/POL nanoparticles depended on the glass transition temperature (T_gH) of the hydrated polymer matrix. Enzymatic effects could not be detected. Nanoparticles with T_gH > 37°C were chemically stable in both gastric and intestinal fluids at 37°C over a time period of more than 48 hr.     

医用聚乳酸材料的化学改性研究进展

聚乳酸是一种常用的可生物降解的医用材料,但单纯聚乳酸并不能满足临床需要.对聚乳酸的改性工作一直都备受关注.综述了近几年聚乳酸生物降解材料的化学改性研究进展,重点论述了共聚、接枝、星型、表面改性4个方面.经改性后聚乳酸的力学性能、降解性能和亲水性能可以得到某些改善,从而更好地满足了生物医用需要.并展望了未来聚乳酸的发展.     

Effect of imidazolium phosphate and multiwalled carbon nanotubes on thermal stability and flame retardancy of polylactide

A series of composites based on polylactide (PLA), have been prepared by melt-blending with multiwalled carbon nanotubes (MWNT) and Tri(1-hydroxyethyl-3-methylimidazolium chloride) phosphate (IP) functionalized MWNT (MIP). The morphology, thermal stability and burning behavior of the composites were investigated by Field Emission Scanning Electron Microscopy (FESEM), Thermogravimetric Analysis (TGA) and Cone Calorimeter Test (CCT), respectively. Significant improvement in fire retardant performance was observed for the PLA/MIP composite from CCT (reducing both the heat release rate and the total heat release) and TGA (increasing the char residue) compared to PLA/MWNT. SEM and Raman spectroscopy were utilized to explore the surface morphology and chemical structure of the char residues. It revealed that the catalytic charring effect of IP, the physical crosslinking effect of MWNT, and the combined effect of both IP and MWNT (forming continuous and compact char layers) were very efficient in improving the flame retarding properties of PLA/MIP composite.     

不同结构的可生物降解聚酯的改性研究

针对PLA、PBS、PPDO三种不同结构的可生物降解聚酯,采用化学和物理改性采提高其综合性能,分析了改性前后化学结构与物理性能的关系,为进一步研究聚酯的降解机理和拓宽其应用领域提供了理论依据和基础数据.     

Fabrication of nanofibrous macroporous scaffolds of poly(lactic acid) incorporating bioactive glass nanoparticles by camphene-assisted phase separation

Here we produced macroporous and nanofibrous scaffolds with bioactive nanocomposite composition, poly(lactic acid) (PLA) incorporating bioactive glass nanoparticles (BGnp) up to 30 wt%, targeting bone regeneration. In particular, the nanofibrous structure in the scaffolds was generated by using a bicyclic monoterpene, camphene (C₁₀H₁₆), through a phase-separation process with PLA-BGnp phase in chloroform/1,4-dioxane co-solvent. Furthermore, macropores were produced by the impregnation of salt particles and their subsequent leaching out, followed by freezing and lyophilization processes. The produced PLA-BGnp scaffolds presented highly porous and nanofibrous structure with porosities of 90–95% and pore sizes of over hundreds of micrometers. BGnp with sizes of ∼90 nm were also evenly impregnated within the PLA matrix, featuring a nanocomposite structure. The nanofibrous scaffolds exhibited enhanced hydrophilicity and more rapid hydrolytic degradation as the incorporated BGnp content increased. The bone-bioactivity of the scaffolds was substantially improved with the incorporation of BGnp, exhibiting rapid formation of apatite throughout the scaffolds in a simulated body fluid. The developed macroporous and nanofibrous scaffolds with PLA-BGnp bioactive composition are considered as a novel 3D matrix potentially useful for bone tissue engineering.     

聚乳酸/杆菌肽静电纺丝纤维的体外释药研究

为探讨聚乳酸纤维结构形貌对杆菌肽药物的缓慢释放行为及作用机理,通过静电纺丝法制备了聚乳酸/杆菌肽单轴纤维、聚乳酸/杆菌肽串珠和(聚乳酸/杆菌肽)-聚乳酸同轴核-壳纤维等聚乳酸/杆菌肽药物缓释体系,并采用红外光谱法和差热分析法对其化学结构和热性能进行了表征.利用紫外分光光度计法研究了不同载药体系的体外药物释放行为,并探索了不同降解时期载药纤维的质量和形貌变化规律.研究表明:杆菌肽与聚乳酸主要为物理结合;聚乳酸单轴纤维和串珠对杆菌肽的扩散释放机理,属于纯Fick扩散;采用单轴和同轴静电纺丝技术可以获得两种不同释药特性的载药纤维.单轴纤维和串珠能够将药物快速释放,适合抗生素的治疗;同轴纤维中药物受控释放,更适合长期、小剂量的药物释放.     

Bioactivity of CaSiO<Subscript>3</Subscript>/poly-lactic acid (PLA) composites prepared by various surface loading methods of CaSiO<Subscript>3</Subscript> powder

Mixing bioactive ceramic powders with polymers is an effective method for generating bioactivity to the polymer-matrix composites but it is necessary to incorporate up to 40 vol% of bioactive ceramic powder. However, such a high mixing ratio offsets the advantages of the flexibility and formability of polymer matrix and it would be highly advantageous to lower the mixing ratio. Since surface loading of ceramic powders in the polymer is thought to be an effective way of reducing the mixing ratio of the ceramic powder while maintaining bioactive activity, CaSiO₃/poly-lactic acid (PLA) composites were prepared by three methods; (1) casting, (2) spin coating and (3) hot pressing. In methods (1) and (2), a suspension was prepared by dissolving PLA in chloroform and dispersing CaSiO₃ powder in it. The suspension was cast and dried to form a film in the case of method (1) while it was spin-coated on a PLA substrate in method (2). In method (3), CaSiO₃ powder was surface loaded on to a PLA substrate by hot-pressing. The bioactivity of these samples was investigated in vitro using simulated body fluid (SBF). Apatite formation was not observed in the samples prepared by method (1) but some apatite formation was achieved by mixing polyethylene glycol (PEG) with the PLA, producing a porous polymer matrix. In method (2), apatite was clearly observed after soaking for 7 days. Enhanced apatite formation was observed in method (3), the thickness of the resulting apatite layers becoming about 20 μm after soaking for 14 days. Since the amount of CaSiO₃ powder used in these samples was only ≤0.4 vol%, it is concluded that this preparation method is very effective in generating bioactivity in polymer-matrix composites by loading with only very small amounts of ceramic powder.     

Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent

Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ζ-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas.     

Bioactive composite gradient coatings of nano-hydroxyapatite/polyamide66 fabricated on polyamide66 substrates

Tightly bonding of bioactive coating is the first crucial need for orthopaedic implants. This study describes a novel and convenient technique to prepare bioactive coating with high adhesion on orthopaedic substitutes made of polymeric matrix. Here, a chemical corrosion method has been adopted to fabricate a coating on the surface of injection-moulded polyamide66 (PA66) substrates by corrosive nano-hydroxyapatite/polyamide66 (n-HA/PA66) composite slurry. Scanning electron microscopy observation shows that a porous chemical corrosion region presents between the coating and dense PA66 substrate. Energy-dispersive X-ray spectroscopy analysis indicates that the chemical corrosion region is mainly composed of PA66 matrix, and the coating layer is an n-HA-rich layer. Both the pore size and n-HA composition increase gradually from the polymeric substrate towards the coating surface. Mechanical testing shows the bonding strength can reach 13.7 ± 0.2 MPa, which is much higher than that fabricated on polymeric matrix by other coating methods. The gradual transition in coating structure and composition benefits for the interface bonding and for the surface bone-bonding bioactivity. Subsequent cell experiments corroborate n-HA-rich coating and a porous structure is benefitting for cell attachment and proliferation. The convenient coating method could be popularized and applied on similar polymer implants to produce a tightly and porous bioactive coating for bone tissue regeneration.