Expression of basal lamina components by Schwann cells cultured on poly(lactic acid) (PLLA) and poly(caprolactone) (PCL) membranes

The present in vitro study investigated the expression of basal lamina components by Schwann cells (SCs) cultivated on PCL and PLLA membranes prepared by solvent evaporation. Cultures of SCs were obtained from sciatic nerves from neonatal Sprague Dawley rats and seeded on 24 well culture plates containing the polymer membranes. The purity of the cultures was evaluated with a Schwann cell marker antibody (anti-S-100). After one week, the cultures were fixed and processed for immunocytochemistry by using antibodies against type IV collagen, laminin I and II. Positive labeling against the studied molecules was observed, indicating that such biomaterials positively stimulate Schwann cell adhesion and proliferation. Overall, the present results provide evidence that membrane-derived biodegradable polymers, particularly those derived from PLLA, are able to provide adequate substrate and stimulate SCs to produce ECM molecules, what may have in turn positive effects in vivo, influencing the peripheral nerve regeneration process.     

Biodegradable poly(lactic acid) microspheres containing total alkaloids of Caulis sinomenii

The fabrication of biodegradable poly(lactic acid) (PLA) microspheres containing total alkaloids of Caulis sinomenii was investigated. The formation, diameter, morphology and properties of the microspheres were characterized using Fourier transform infrared spectroscopy (FT-IR), laser particle size analyser and scanning electron microscopy (SEM), etc. In vitro releasing behaviour was also investigated using UV-Vis spectrometer. As a result, the drug-loaded microspheres with a narrower distributive, rounder and smoother surface were prepared. Drug-releasing behaviour from microspheres was affected by the concentration of emulsifier and the stirring rate. The results demonstrated that a medicated system, which can be potentially applied within a drug delivery system, was designed. This system acts in a systematic manner for the treatment of rheumatoid arthritis.     

Nanodiamond/poly (lactic acid) nanocomposites: Effect of nanodiamond on structure and properties of poly (lactic acid)

Nanodiamond (ND)/poly (lactic acid) (PLA) nanocomposites with potential for biological and biomedical applications were prepared by using melting compound methods. By means of transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analyses (TGA), Dynamic mechanical analyses (DMA), Differential scanning calorimetry (DSC) and Tensile test, the ND/PLA nanocomposites were investigated, and thus the effect of ND on the structural, thermal and mechanical properties of polymer matrix was demonstrated for the first time. Experimental results showed that the mechanical properties and thermal stability of PLA matrix were significantly improved, as ND was incorporated into the PLA matrix. For example, the storage modulus (E′) of 3 wt% ND/PLA nanocomposites was 0.7 GPa at 130 °C which was 75% higher than that of neat PLA, and the initial thermal decomposition was delayed 10.1 °C for 1 wt% ND/PLA nanocomposites compared with the neat PLA. These improvements could be ascribed to the outstanding physical properties of ND, homogeneous dispersion of ND nanoclusters, unique ND bridge morphology and good adhesion between PLA matrix and ND in the ND/PLA nanocomposites.     

聚乳酸的聚合方法

本文探讨了聚乳酸的现有聚合方法 ,同时对聚乳酸的另一直接 -固相新聚合方法进行了研究 ,分析了聚乳酸固相聚合机理 ,通过实验验证了固相聚合方法的有效性     

聚乳酸纤维的研究进展

聚乳酸是一种新型的生态环保型高分子材料.本文主要介绍了世界各国对聚乳酸纤维研究及生产的相关情况,对聚乳酸的生产工艺作了深入的探究,并介绍了聚乳酸的应用及发展前景.     

聚乳酸的增塑改性

采用溶液共混法,以聚乙二醇(PEG)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二辛酯(DOP)作为增塑剂,对聚左旋乳酸(PLA)进行增塑改性.用综合热分析仪对改性PLA的热性能进行了表征.讨论了不同的增塑剂及其用量对改性PLA性能的影响:当增塑剂的含量增加时,改性PLA的强度下降,伸长率增加,并逐渐由脆性向韧性转变;玻璃化转变温度(Tg)和熔点(Tm)下降.当增塑剂的质量比≤20%时,共混物各组分间有较好的相容性.PEG400改性的PLA效果较好.     

Drug delivery systems using sandwich configurations of electrospun poly(lactic acid) nanofiber membranes and ibuprofen

The primary advantages of electrospun membranes include the ability to obtain very thin fibers that are on the order of magnitude of several nanometers with a considerable superficial area and the possibility for these membranes to be manipulated and processed for many different applications. The purpose of this study is to evaluate and quantify the transport mechanisms that control the release of drugs from polymer-based sandwich membranes produced using the electrospinning processes. These electrospun membranes were composed of poly(lactic acid) (PLA) because it is one of the most promising biodegradable polymers due to its mechanical properties, thermoplastic processability and biological properties, such as its biocompatibility and biodegradability. The transport mechanism that controls the drug delivery was evaluated via the release kinetics of a bioactive agent in physiological serum, which was used as a corporal fluid simulation. To describe the delivery process, mathematical models, such as the Power Law, the classical Higuchi equation and an approach to Fick's Second Law were used. Using the applied mathematical models, it is possible to conclude that control over the release of the drug is significantly dependent on the thickness of the membrane rather than the concentration of the drug.     

聚乳酸类组织工程支架材料的设计

聚乳酸无毒、易加工、可生物降解、生物相容性好,是目前医学界作为组织工程支架最有开发和应用潜力一类材料。从材料的制备、支架的加工、生物学评价三方面出发,结合本课题组的研究,论述了聚乳酸类支架的设计,并对今后的研究做了进一步展望。     

Fabrication of poly(lactic acid)-poly(ethylene oxide) electrospun membranes with controlled micro to nanofiber sizes

Biodegradable poly(L-lactide acid) (PLLA) nanofiber membranes were prepared by electrospinning of PLLA and poly(ethylene oxide) (PEO). The selective removal of PEO by water allows to obtain smaller fiber diameters and to increase the porosity of the membranes in comparison to PLLA membranes obtained under the same electrospinning conditions. After removal of PEO membranes with fiber sizes of 260 nm and average porosity close to 80% are obtained. Thermal and infrared results confirm the poor miscibility of PLLA and PEO, with the PEO randomly distributed along the PLLA fibers. On the other, PLLA and PEO mixing strongly affect their respective degradation temperatures. The influence of the PEO in the electrospinning process is discussed and the results are correlated to the evolution of the PLLA fiber diameter.     

端羧基聚乳酸共聚物的合成及表征

以乳酸为原料,辛酸亚锡为催化剂,采用梯度升温法,在168℃、0.098MPa下直接熔融缩聚生成端羧基聚乳酸共聚物P(LA/SA)、P(LA/CA)和P(LA/AC).用乌氏粘度法、FT-IR、1H-NMR、DSC、TGA及XRD等对共聚物进行了表征.结果表明和PLA相比,3种端羧基共聚物Tg均有不同程度的降低,说明端羧...     

新型生物降解材料聚乳酸的微孔发泡技术研究进展

介绍了新型生物可降解材料聚乳酸(PLA)微孔塑料的最新研究进展,并详细介绍了PLA微孔塑料的泡孔形态和力学性能的影响因素.     

Scaffolds for drug delivery,part I: electrospun porous poly(lactic acid) and poly(lactic acid)/poly(ethylene oxide) hybrid scaffolds

This is the first in a series of papers, focused on the development of a biodegradable, controlled, and potentially targeted drug delivery system. In this paper, we describe the production of highly porous biodegradable fibrous structures suitable for biomedical applications and as a matrix for drug delivery. Two structures are described below. The first structure is composed of electrospun poly(lactic acid) (PLA) fibers and is unique due to (1) the uniformity if its constitute fibers’ diameter, (2) consistent surface pore dimensions of each fiber, (3) the use of only a single solvent, (4) interior nano-size porosity throughout each individual fiber, and (5) the independency of surface pore dimensions on fiber diameter. The produced matrix will be further impregnated with cargo loaded nanoparticles—Red clover necrotic mosaic virus (RCNMV)—to achieve a controlled drug delivery system (described in Part III) for cancer treatments. Such a structure can also be used as tissue engineering scaffolds and filter media. The second electrospun structure has enhanced hydrophilicity compared to PLA matrix and is formed by blending poly(lactic acid)/poly(ethylene oxide) (PEO) polymers. The incorporation of PEO in the matrix introduces preferable sites for aqueous compounds to be attached to while retaining the overall structural integrity and porous morphology. It is hypothesized that the existence of alternative hydrophilic and hydrophobic segments in the structure may reduce post-implantation complications such as platelet adhesion.     

Multi-walled carbon nanotubes and poly(lactic acid) nanocomposite fibrous membranes prepared by solution blow spinning

Nanocomposite fibers based on multi-walled carbon nanotubes (MWCNT) and poly(lactic acid) (PLA) were prepared by solution blow spinning (SBS). Fiber morphology was characterized by scanning electron microscopy (SEM) and optical microscopy (OM). Electrical, thermal, surface and crystalline properties of the spun fibers were evaluated, respectively, by conductivity measurements (4-point probe), thermogravimetric analyses (TGA), differential scanning calorimetry (DSC), contact angle and X-ray diffraction (XRD). OM analysis of the spun mats showed a poor dispersion of MWCNT in the matrix, however dispersion in solution was increased during spinning where droplets of PLA in solution loaded with MWCNT were pulled by the pressure drop at the nozzle, producing PLA fibers filled with MWCNT. Good electrical conductivity and hydrophobicity can be achieved at low carbon nanotube contents. When only 1 wt% MWCNT was added to low-crystalline PLA, surface conductivity of the composites increased from 5 x 10(-8) to 0.46 S/cm. Addition of MWCNT can slightly influence the degree of crystallinity of PLA fibers as studied by XRD and DSC. Thermogravimetric analyses showed that MWCNT loading can decrease the onset degradation temperature of the composites which was attributed to the catalytic effect of metallic residues in MWCNT. Moreover, it was demonstrated that hydrophilicity slightly increased with an increase in MWCNT content. These results show that solution blow spinning can also be used to produce nanocomposite fibers with many potential applications such as in sensors and biosensors.     

Novel lightweight sandwich-structured bio-fiber-reinforced poly(lactic acid) composites

Novel bio-based lightweight sandwich-structured composites with both skin and core materials made from biofiber and poly(lactic acid) (PLA) matrix were developed. The composites contained 48 wt% cellulose fiber and 52 wt% PLA matrix. The fabrication process was simple and required no adhesive for the skin–core bonding. The effects of fiber weight fraction and density on the core compressive properties were evaluated experimentally. Fifty percent of fibers gave the best results among the three fiber weight fractions studied and was used in preparing cores for subsequent fabrication of the sandwich-structured composites. The flexural properties and failure modes of the sandwich-structured composites were assessed. The flexural properties of the composites met the published deflection requirements for automotive load floor applications. Since these biocomposites were made using natural renewable materials that are fully biodegradable and recyclable, they show potential to be used as environmentally friendly alternatives to the existing products.     

Development of poly(lactic acid) nanostructured membranes for the controlled delivery of progesterone to livestock animals

Solution blow spinning (SBS) is a novel technology feasible to produce nanostructured polymeric membranes loaded with active agents. In the present study, nanofibrous mats of poly(lactic acid) (PLA) loaded with progesterone (P4) were produced by SBS at different P4 concentrations. The spun membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The in vitro releasing of P4 was evaluated using high-performance liquid chromatography (HPLC). Interactions between progesterone and PLA were confirmed by rheological measurements of the PLA/P4 solutions and in the spun mats by microscopy (SEM), thermal (DSC) and spectral (FTIR) analyses. SEM micrographs provided evidences of a smooth and homogeneous structure for nanostructured membranes without progesterone crystals on fiber surface. FTIR spectroscopy indicated miscibility and interaction between the ester of PLA and the ketone groups of the P4 in the nanofibers. X-ray analysis indicated that the size of PLA crystallites increased with progesterone content. Finally, by in vitro release experiments it was possible to observe that the progesterone releasing follows nearly first-order kinetics, probably due to the diffusion of hormone into PLA nanofibers.     

乳酸-氨基酸共聚物的制备及研究发展

制备乳酸-氨基酸共聚物是改性聚乳酸的有效方法之一。综述了近年来乳酸-氨基酸共聚物的制备方法与特点,指出了较高分子量和高氨基酸含量聚合物的制备工艺是研发的重点。     

The effects of cellulose nanowhiskers on electrospun poly (lactic acid) nanofibres

The effects of cellulose nanowhiskers on the microstructure and thermal behaviour of electrospun poly (lactic acid) (PLA) nanofibres have been investigated in this study. The PLA/cellulose nanowhiskers composite nanofibres are successfully produced by electrospinning the mixtures of cellulose whiskers with PLA solution. The diameters of PLA and its composites are around 300 nm. The scanning electron micrographs show that the cellulose nanowhiskers do not protrude out of the outer surfaces of PLA nanofibres. The existence of cellulose nanowhiskers in the electrospun PLA matrix nanofibres, and the microstructural evolution are investigated by using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) analysis shows the formation trend of PLA α crystal with the addition of cellulose nanowhiskers. The electrospun PLA and PLA/cellulose nanowhiskers composites reveal very low crystallinity due to the rapid solvent evaporation and relatively slow crystallisation kinetics character of PLA. The electrospun nanofibres show particularly different thermal behaviour from that of the solution cast films. The nanofibres of pure PLA and PLA/cellulose nanowhiskers experience two consecutively overlapping crystallisation processes. The cellulose nanowhiskers act as heterogeneous sites for nucleation of PLA by decreasing the cold crystallisation onset temperature. The incorporation of cellulose nanowhiskers into PLA nanofibres is expected to improve mechanical properties and bring new functionalities to the electrospun matrix nanofibres.