BCNU-loaded PEG-PLLA ultrafine fibers and their in vitro antitumor activity against glioma C6 cells

The purpose of the present study was to develop implantable BCNU-toaded poly(ethylene glycol)poly(L-lactic acid) (PEG-PLLA) diblock copolymer fibers for the controlled release of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). BCNU was well incorporated and dispersed uniformly in biodegradable PEG-PLLA fibers by using electrospinning method. Environmental Scanning Electron Microscope (ESEM) images indicated that the BCNU-loaded PEG-PLLA fibers looked uniform and their surfaces were reasonably smooth. Their average diameters were below 1500 nm. The release rate of BCNU from the fiber mats increased with the increase of BCNU loading amount. In vitro cytotoxicity assay showed that the PEG-PLLA fibers themselves did not affect the growth of rat Glioma C6 cells. Antitumor activity of the BCNU-loaded fibers against the cells was kept over the whole experiment process, while that of pristine BCNU disappeared within 48 h. These results strongly suggest that the BCNU/PEG-PLLA fibers have an effect of controlled release of BCNU and are suitable for postoperative chemotherapy of cancers.

Ultrafine fibers electrospun from biodegradable polymers

Biodegradable poly(I-lactide) (PLLA) and poly(e-caprolactone) (PCL) were electrospun into ultrafine fibers. The technological parameters influencing the spinning process and morphology of the fibers obtained were examined. These parameters included solvent composition, addition of certain organic salts, molecular weight and concentration of the polymers, capillary diameter, air ventilation, and pressure imposed on the surface of the solution as well as electrostatic field. By properly choosing and adjusting these parameters, submicron PLLA and PCL fibers with a narrow diameter distribution were prepared. Scanning electronic microscopy was used to observe the morphology and diameter size of the fibers.

The immobilization of proteins on biodegradable polymer fibers via click chemistry

A facile and efficient method to immobilize bioactive proteins onto polymeric substrate was established. Testis-specific protease 50 (TSP50) was immobilized on ultrafine biodegradable polymer fibers, i.e., (1) to prepare a propargyl-containing polymer P(LA90-co-MPCIO) by introducing propargyl group into a cyclic carbonate monomer (5-methyl-5-propargyloxycarbonyl-1,3-dioxan2-one, MPC) and copolymerizing it with L-lactide; (2) to electrospin the functionalized polymer into ultrafine fibers; (3) to azidize the TSP50, and (4) to perform the click reaction between the propargyl groups on the fibers and the azido groups on the protein.

The release behavior of doxorubicin hydrochloride from medicated fibers prepared by emulsion-electrospinning

The release behavior of a water-soluble small molecule drug from the drug-loaded nanofibers prepared by emulsion-electrospinning was investigated. Doxorubicin hydrochloride (Dox), a water-soluble anticancer agent, was used as the model drug. The laser scanning confocal microscopic images indicated that the drug was well incorporated into amphiphilic poly(ethylene glycol)-poly(L-lactic acid) (PEG-PLA) diblock copolymer nanofibers, forming "core-sheath" structured drug-loaded nanofibers.

PLLA-PCys co-electrospun fibers for capture and elution of glutathione S-transferase

The copolymer poly(L-lactic acid)-b-poly(L-cysteine) (PLA-b-PCys) was co-electrospun with PLGA into ultrafine fibers. The reduced glutathione (GSH) was conjugated to the fiber surfaces via disulfide bonds. The glutathione S-transferase (GST) was captured onto the GSH fibers via specific substrate-enzyme interaction between the bound GSH and GST. The captured GST was eluted with free GSH aqueous solution and lyophilized to get pure GST powders. The results show that the GSH moieties on the fiber surface retain the bioactivity of the free GSH and thus they can bind specifically with GST and the GST in solution is captured onto the fiber surface. In addition, the bound GSH is not as active as free GSH so that the captured GST can be eluted off from the fiber by free GSH aqueous solution. Based on this principle, GST itself or its fused proteins can be separated and purified very easily. The preliminary purification efficiency is 6.5 mg center dot(g(PCys))(-1). Further improvements are undertaken.

Enzymatic degradation of poly(L-lactide) and poly (epsilon-caprolactone) electrospun fibers

Poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) ultrafine fibers were prepared by electrospinning. The influence of cationic and anionic surfactants on their enzymatic degradation behavior was investigated by measuring weight loss, molecular weight, crystallinity, and melting temperature of the fibers as a function of degradation time. Under the catalysis of proteinase K, the PLLA fibers containing the anionic surfactant sodium docecyl sulfate (SDS) exhibited a faster degradation rate than those containing cationic surfactant triethylbenzylammonium chloride (TEBAC), indicating that surface electric charge on the fibers is a critical factor for an enzymatic degradation. Similarly, TEBAC-containing PCL fibers exhibited a 47% weight loss within 8.5 h whereas SDS-containing PCL fibers showed little degradation in the presence of lipase PS. By analyzing the charge status of proteinase K and lipase PS under the experimental conditions, the importance of the surface charges of the fibers and their interactions with the charges on the enzymes were revealed. Consequently, a "two-step" degradation mechanism was proposed: (1) the enzyme approaches the fiber surface; (2) the enzyme initiates hydrolysis of the polymer.

Biodegradable electrospun poly(L-lactide) fibers containing antibacterial silver nanoparticles

Biodegradable poly(L-lactide) (PLA) ultrafine fibers containing nanosilver particles were prepared via electrospinning. Morphology of the Ag/PLA fibers and distribution of the silver nanoparticles were characterized. The release of silver ions from the Ag/PLA fibers and their antibacterial activities were investigated. These fibers showed antibacterial activities (microorganism reduction) of 98.5% and 94.2% against Staphylococcus aureus and Escherichia coli, respectively, because of the presence of the silver nanoparticles.

可生物降解电纺丝超细纤维

电纺丝技术是一种用来制备超细纤维的方法，成本低廉、简单易行。近十年来，电纺丝技术在理论研究和实验参数研究等方面都取得了不小的进展。由电纺丝技术制备的超细纤维直径至少比传统的纺丝工艺低1-3个数量级，因此，在增强复合材料、过滤系统、防护衣、光学和电学器件及生物医药等方面都显示出巨大的应用潜力。尤其是在生物医药领域，电纺丝超细纤维可广泛用作组织工程支架、药物传输与控制释放的载体及创伤敷料等，这也是国际上的一个研究热点。但由于电纺丝过程的复杂性和实验参数的多样性，制备直径分布范围窄的纤维一直是电纺丝的难点之一，另外，以电纺丝超细纤维作为药物传输与释放的载体也是近两年才刚刚发展起来的，还不十分成熟，经常会存在药物的突释现象。针对以上问题，本论文以可生物降解高分子材料PLA、PLGA（80／20）和PCL进行电纺丝，系统地研究了溶剂体系、表面活性剂、鲜溶液流速、喷丝口直径及环境温度与空气流动速度等因素对电纺丝过程及纤维形貌和直径分布的影响，同时对电纺丝纤维的性质进行了分析。在此基础上，我们研究了PLLA和PCL电纺丝超细纤綷的酶降解行为，并实现了PLLA纤维对抗癌药紫杉醇和1. 以氯仿、氯仿/丙酮、1、2-二氯乙烷及氯仿/1,2-氯乙烷为溶剂体系，制备了PLA、PCL和PLGA（80／20）的电纺丝超细纤维。当氯仿与丙酮的体积比为1：1时为最佳溶剂体系，电纺丝过程和纤维形貌都得到较大的改善。阳离子表面活性剂节基三乙基氯化按（TBBAC）和阴离子表面活性剂十二烷基硫酸钠（SDS）的加入也可以显著改善电纺丝过程和纤维的直径分布，而非离子表面活性剂脂肪醇聚氧乙烯醚（AEO10）的改善程度较小。压力较大或喷丝口直径较粗时，则会由于溶液流量的增大而造成纤维的粘连。空气流速较大时，则纤维会由于空气的对流速度加快而发生缠绕和卷曲。2．PLLA、PCL和PLGA（80／20）超细纤维毡的孔隙率都较大，分别达到89％、68％和80％，因此，PLLA和PCL纤维的力学性能都远远低于膜。3．电纺丝过程会使纤维中的高分子链产生一定的排列和高度的取向，但由于纤维的固化速度很快，高分子链来不及进行规整排列而形成结晶，因此，DSC和WXAD的结果都显示，PCL纤维毡的结晶度要比相应的膜低。对于PLLA纤维毡来说，由于Tg在室温以上，在进行DSC测试的升温过程中，会由于分子链的运动而使结晶度升高。4．蛋白酶K在Tris-HCL缓冲液中略显正电性，因而阴离子表面活性剂对蛋白酶K会有一定的吸附作用，而阳离子表面活性剂对蛋白酶K在纤维表面的吸附则有一定的阻碍作用，因此，含有5wt％SDS的PLLA纤维的酶降解速率比含有swt％TEBAC的PLLA纤维稍快。虽然纤维中PLLA的分子链可能高度取向，但在整个降解过程中，PLLA纤维样品都处在非晶状态，没有明显的结晶行为。5．与PLLA纤维的降解情况恰好相反，由于脂肪酶PS在磷酸盐缓冲液（PBS）缓冲液中显示较强的负电性，因而阳离子表面活性剂TEBAC会对脂肪酶PS有吸附作用，从而含有5wt％TEBAC的PCL纤维降解速度较快，而阴离子表面活性剂SDS会对脂肪酶PS在纤维表面的吸附有阻碍作用，因此，降解反应在含有5wt％SDS的PCL纤维中几乎不能发生。DSC和WAXD的结果均显示，在降解过程中，含有5wt％TEBAC的PCL纤维的结晶度明显升高。这有两个可能原因：一是脂肪酶PS对PCL纤维的降解是优先发生在无定形区：二是因为降解实验是在37℃的条件下进行的，该温度在PCL的Tg之上和TC温度附近，因而，具有高度排列和取向的PCL纤维就会由于分子链的运动而产生结晶，造成结晶度的提局。6，在电纺丝溶液中加入利福平、紫杉醇和阿霉素等药物，同样会改善电纺丝过程，使纤维直径降低，分布变窄。7．SEM照片和药物控制释放实验均显示，药物模型利福平或抗癌药紫杉醇完全被包埋在PLLA纤维内部，同时，利福平一PLLA纤维和紫杉醇－PLLA纤维在含蛋白酶K的Tris-HCl缓冲液中的释放遵循零级动力学，完全没有突释现象。PLLA纤维的降解速度是药物释放的主导因素。这是在国际范围内首次取得这样的结果，从而使电纺丝超细纤维药物剂型的发展取得了本质上的进步。8．药物在溶剂体系中的溶解性及与高分子材料的相容性是影响药物能否被纤维成功包埋的直接因素，一般脂溶性药物易于被脂溶性的高分子纤维包埋。因此，水溶性的盐酸阿霉素难于被包埋在脂溶性的PLLA纤维内部，在纤维外面和表面存在大量盐酸阿霉素的颗粒。相应地，其药物释放行为存在明显的突释现象，这主要是由纤维外面和表面的盐酸阿霉素的溶解、扩散造成的。而经去盐酸化的阿霉素的脂溶性较好，因此，在PLLA纤维中的包埋及释放行为均得到明显的改善，可实现阿霉素的恒速释放，无突释行为。9．SEM照片显示，药物模型利福平被完全包埋在PLGA（80／20）纤维内部，利福平-PLGA（80／20）纤维在PBS中的释放速率是随着纤维中利福平含量的增加而增加的，利福平的含量越大，其释放速率越快。在释放前期，利福平的扩散起主导作用，而在释放后期，其释放行为则是利福平扩散和PLGA（80／20）降解的双重作用结果。适当增加利福平在纤维中的含量（30wt％），则可以获得恒速的释放行为。10．PBS中TEBAC或SDS浓度的增加会在一定程度上使利福平-PLGA（80／20）纤维的释放速率加快，这主要是由于表面活性剂会降低PBS的表面张力，增加水对PLGA（80／20）纤维的浸润能力，从而加快了利福平的扩散速度。

Bacterial cellulose from glucanacetobacter xylinus: Preparation, properties and applications

This chapter deals with the cellulose produced by the Glucanacetobacter xylinus strain, called bacterial cellulose, which is a remarkably versatile biomaterial usable in wide variety of domains, such as papermaking, optics, electronics, acoustics, and biomedical devices. Its unique structure shows entangled ultrafine fibers, which provide excellent mechanical strength, besides biodegradability, biocompatibility, high water-holding capacity, and high crystallinity. Some of its applications are described, such as complementary nutrition (. nata de coco), artificial temporary skin for wounds and burns, dental aid, artificial blood vessels and micronerve surgery, DNA separation, composite reinforcement, electronic paper, light emitting diodes, and fuel cell membranes. © 2007 Elsevier Ltd. All rights reserved.

Ultrafine PEG-PLA fibers loaded with both paclitaxel and doxorubicin hydrochloride and their in vitro cytotoxicity

By means of "emulsion-electrospinning", both hydrophobic and hydrophilic drugs, paclitaxel (PTX) and doxorubicin hydrochloride (DOX), were successfully loaded into PEG-PLA nanofiber mats to realize multi-drug delivery. The release behaviors of both the drugs from the same fiber mats were ascribed to their solubility properties and distribution status in the fibers. Due to its high hydrophilicity, DOX was easy to diffuse out from the fibers, and its release rate was always faster than that of hydrophobic PTX. Moreover, the release rate of PTX was accelerated by DOX's release from the same drug-loaded fibers. In vitro cytotoxicity against rat Glioma C6 cells indicated that the dual drug combination showed a higher inhibition and apoptosis against C6 cells than a single drug-loaded system, which suggests the promise for multi-drug delivery on combination therapy.

Syndiotactic 1,2-polybutadiene fibers produced by electrospinning

Syndiotactic 1,2-polybutadiene (s-PB) is a typical thermoplastic elastomer with various applications because of its high reactivity. In the past, it is difficult to form s-PB fibers with a diameter below 10 mu m because of the limitation of the conventional method such as melt spinning. Here, we report for the first time on the production of s-PB nanofibers by using a simple electrospinning method. Ultrafine s-PB fibers without beads were electrospun from s-PB solutions in dichloromethane and characterized by environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). At 4 wt.% concentration of s-PB, the average diameter of s-PB was about 130 nm. We found that dichloromethane was a unique suitable solvent for the electrospinning of s-PB fibers, and the structure of syndiotactic was changed through the electrospinning process.

Biodegradable electrospun fibers for drug delivery

The influences of surfactants and medical drugs on the diameter size and uniformity of electrospun poly(L-lactic acid) (PLLA) fibers were examined by adding various surfactants (cationic, anionic, and nonionic) and typical drugs into the PLLA solution. Significant diameter reduction and uniformity improvement were observed. It was shown that the drugs were capsulated inside of the fibers and the drug release in the presence of proteinase K followed nearly zero-order kinetics due to the degradation of the PLLA fibers. Such ultrafine fiber mats containing drugs may find clinical applications in the future.

On the efficiency of impingers with fritted nozzle tip for collection of ultrafine particles

The aim of this study was to determine the collection efficiency of ultrafine particles into an impinger fitted with a fritted nozzle tip as a means to increase contact surface area between the aerosol and the liquid. The influence of liquid sampling volume, frit porosity and the nature of the sampling liquid was explored and it was shown that all impact on the collection efficiency of particles smaller than 220 nm. Obtained values for overall collection efficiency were substantially higher (~30–95%) than have been previously reported, mainly due to the high deposition of particles in the fritted nozzle tip, especially in case of finer porosity frits and smaller particles. Values for the capture efficiency of the solvent alone ranged from 20 to 45%, depending on the type and the volume of solvent. Additionally, our results show that airstream dispersion into bubbles improves particle trapping by the liquid and that there is a difference in collection efficiencies based on the nature and volume of the solvent used.

Comparison of ultrafine particle release from hardcopy devices in emission test chambers and office rooms

The release of ultrafine particles (UFP) from laser printers and office equipment was analyzed using a particle counter (FMPS; Fast Mobility Particle Sizer) with a high time resolution, as well as the appropriate mathematical models. Measurements were carried out in a 1 m³ chamber, a 24 m³ chamber and an office. The time-dependent emission rates were calculated for these environments using a deconvolution model, after which the total amount of emitted particles was calculated. The total amounts of released particles were found to be independent of the environmental parameters and therefore, in principle, they were appropriate for the comparison of different printers. On the basis of the time-dependent emission rates, “initial burst” emitters and constant emitters could also be distinguished. In the case of an “initial burst” emitter, the comparison to other devices is generally affected by strong variations between individual measurements. When conducting exposure assessments for UFP in an office, the spatial distribution of the particles also had to be considered. In this work, the spatial distribution was predicted on a case by case basis, using CFD simulation.

On-road ultrafine particle concentration in the M5 East road tunnel, Sydney, Australia

The human health effects following exposure to ultrafine (<100nm) particles (UFPs) produced by fuel combustion, while not completely understood, are generally regarded as detrimental. Road tunnels have emerged as locations where maximum exposure to these particles may occur for the vehicle occupants using them. This study aimed to quantify and investigate the determinants of UFP concentrations in the 4km twin-bore (eastbound and westbound) M5 East tunnel in Sydney, Australia. Sampling was undertaken using a condensation particle counter (CPC) mounted in a vehicle traversing both tunnel bores at various times of day from May through July, 2006. Supplementary measurements were conducted in February, 2008. Over three hundred transects of the tunnel were performed, and these were distributed evenly between the bores. Additional comparative measurements were conducted on a mixed route comprising major roads and shorter tunnels, all within Sydney. Individual trip average UFP concentrations in the M5 East tunnel bores ranged from 5.53 × 104 p cm-3 to 5.95 × 106 p cm-3. Data were sorted by hour of capture, and hourly median trip average (HMA) UFP concentrations ranged from 7.81 × 104 p cm-3 to 1.73 × 106 p cm-3. Hourly median UFP concentrations measured on the mixed route were between 3.71 × 104 p cm-3 and 1.55 × 105 p cm-3. Hourly heavy diesel vehicle (HDV) traffic volume was a very good determinant of UFP concentration in the eastbound tunnel bore (R2 = 0.87), but much less so in the westbound bore (R2 = 0.26). In both bores, the volume of passenger vehicles (i.e. unleaded gasoline-powered vehicles) was a significantly poorer determinant of particle concentration. When compared with similar studies reported previously, the measurements described here were among the highest recorded concentrations, which further highlights the contribution road tunnels may make to the overall UFP exposure of vehicle occupants.