乳酸-乙醇酸共聚物/壳聚糖复式微球缓释蛋白

采用两次乳化包埋技术制备了一种载蛋白的乳酸-乙醇酸共聚物/壳聚糖复式微球（Poly（lactide-co-glycolide）/chitosan微球,简称PLGA/chitosan微球）。先以复乳法（W/O/W）制备加载牛血清白蛋白（BSA）的PLGA微球,再以壳聚糖（Chitosan）为基体对PLGA微球进行包埋,用...     

Electrospinning highly oriented and crystalline poly(lactic acid) fiber mats

In recent years, there has been an increased focus on sustainable, green alternatives with similar properties to conventional petroleum-based polymers. Poly(lactic acid) (PLA) is a biodegradable biopolymer which exhibits mild piezoelectric properties and has good processability which gives it potential for use in numerous existing and novel applications. The purpose of this study was to produce highly oriented and crystalline PLA electrospun fiber mats for piezoelectric applications. In order to yield a high piezoelectric constant, high crystallinity and fiber orientation are necessary. A two parallel collector set up was used to mechanically orient the fibers in the space between two copper electrodes. Voltage and feed rate were adjusted to produce smooth, oriented fibers with average diameters ranging 0.73–1.19 μm. Crystallinity and orientation were increased via hot drawing of the fiber mats and were maximized between 40 and 50 % and greater than 50 %, respectively.     

Controlled release of salicylic acid from poly(D,L-Lactide)

Poly(D,L-Lactide) of high molecular weight (M_v was prepared by ring-opening bulk polymerization of D,L-Lactide and characterized in terms of M_v, melting point and swelling behavior in buffer solution. Samples of the polymers with low and high M_v (2000 and 22 000 respectively) loaded with various amounts of salicylic acid (SA) were immersed in a buffer solution and the release of SA was recorded. The results obtained showed that swelling of the poly(D,L-Lactide) samples obeyed Fick's law, especially for those with high molecular weight, where biodegradation proceeds slowly. The release of SA seemed to follow a simplified relationship which is linear with time, at least for the early stages of delivery. The extent of linearity is dependent on the content of the acidic SA, which probably accelerates decomposition of the high molecular weight products. © 2001 Kluwer Academic Publishers     

Study on hydrophilic 5-fluorouracil release from hydrophobic poly(ϵ-caprolactone) cylindrical implants

Hydrophilic 5-fluorouracil (5-FU) loaded cylindrical poly(?-caprolactone) (PCL) implants with different implant diameters (2, 4 and 8?mm), different drug loadings (25% and 50%) and end-capping were fabricated and characterized. The implant structure, drug content and molecular weight of PCL after 120 days drug release were investigated. The in vitro release results showed that, when the drug loading was the same, drug release was fastest for the implant with a diameter of 2?mm and slowest for the implant with a diameter of 8?mm; for the implants with the same diameters, the release of drug from the implants with 50% drug loading was faster than that from the implants with 25% drug loading; however, this effect of drug loading decreased with the increase of implant diameter; in addition, 5-FU was released slightly slower from the end-capped implants than from the corresponding uncapped implants; the drug release data for all the uncapped implants were best fit with the Ritger-Peppas model. Drug release from the hydrophobic implants was found to be dominated by diffusion mechanism. Scanning electron microscopy images and drug content measurements revealed that 5-FU release took place gradually from the exterior region to the interior region of the implants.     

Dual delivery of hydrophilic and hydrophobic drugs from chitosan/diatomaceous earth composite membranes

Oral administration of drugs presents important limitations, which are frequently not granted the importance that they really have. For instance, hepatic metabolism means an important drug loss, while some patients have their ability to swell highly compromised (i.e. unconsciousness, cancer…). Sublingual placement of an accurate Pharmaceutical Dosage Form is an attractive alternative. This work explores the use of the β-chitosan membranes, from marine industry residues, composed with marine sediments for dual sublingual drug delivery. As proof of concept, the membranes were loaded with a hydrophilic (gentamicin) and a hydrophobic (dexamethasone) drug. The physico-chemical and morphological characterization indicated the successful incorporated of diatomaceous earth within the chitosan membranes. Drug delivery studies showed the potential of all formulations for the immediate release of hydrophilic drugs, while diatomaceous earth improved the loading and release of the hydrophobic drug. These results highlight the interest of the herein developed membranes for dual drug delivery.

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Preparation and release characteristic of quercetin loaded poly(lactic acid) ultrafine fibers

In this study, poly(lactic acid) (PLA) ultrafine fibers have been prepared by electrospinning method using mix-solvent. The results showed that the variation of solvent ratio (N,N-dimethylformamide (DMF)/Dichloromethane (DCM)) could change the surface morphology of PLA nanofibers. By adjusting the solvent ratio, the quercetin release rate from the fiber membranes could be controlled. Furthermore, by adjusting the PLA concentration, the nanofibers without beads could be obtained. After addition of quercetin to polymer solution, the spindle-shaped beads on the fiber disappeared, but surface morphology of the fiber changed little with increase in quercetin dosage, and the release rate of quercetin increased with increase of quercetin dosage.     

Plasma surface treatments of poly(l-lactic acid) (PLLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)

The surfaces of poly(l-lactic acid) (PLLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) were modified by oxygen and nitrogen plasma treatments. The physical and chemical surface characteristics were evaluated by contact angle tests, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The plasma treatments caused an increase in both contact angle and roughening, altered the surface morphology, inserted polar groups, and, consequently, enhanced the hydrophilicity for both PLLA and PHBV polymers.     

pH dependent hydrolysis and drug release behavior of chitosan/poly(ethylene glycol) polymer network microspheres

Semi-interpenetrating polymer network (IPN) microspheres of chitosan and poly(ethylene glycol) PEG were prepared for controlled release of drugs. A new method for the chemical crosslinking of chitosan microspheres containing isoniazid (INH) as a model drug is proposed and evaluated. The method consists of the exposure of microspheres to the vapor of crosslinking agent that act in gaseous phase under mild conditions. The structural analysis of the microspheres was carried out by FTIR-analysis. The swelling behavior, hydrolytic degradation, structural changes of the microspheres and loading capacity (LC) of the microspheres for INH were investigated. The prepared microspheres have shown 93% drug loading capacity, which suggested that these semi-IPN microspheres are suitable for controlled release of drugs in an oral sustained delivery system. © 2001 Kluwer Academic Publishers     

Study on sound absorption property of ramie fiber reinforced poly(l-lactic acid) composites: Morphology and properties

The effect of ramie fiber, flame retardant and plasticizer on sound absorption property of ramie fiber reinforced PLLA composites was investigated. We used press molding process to prepare the ramie fiber/PLLA composites, with short ramie fiber and ramie plain weave fabric as the reinforcement. The dispersivity of flame retardant ammonium polyphosphate (APP) was indirectly tested by thermogravimetric analysis (TGA). The result of sound absorption property measurement shows that the composites with short ramie fiber have better sound absorption property than the ramie fabric reinforced PLLA composites. And the addition of APP and plasticizer poly(butylene adipate-co-terephthalate) (PBAT) improves the sound absorption property of ramie fabric/PLLA composites. Moreover, morphological studies by scanning electron microscopy (SEM) demonstrate the micro-phase separation in the PBAT/PLLA composites and the porosity of the single ramie fiber bundle. The results suggest that these special structures are the main reason for the better sound absorption property.     

纳米纤维素增强聚乙烯醇/水性聚氨酯静电纺膜的研究

采用TEMPO(2,2,6,6-四甲基哌啶氧化物自由基)氧化纤维素纳米纤维(TOCNs)作为聚乙烯醇(PVA)/水性聚氨酯(WPU)静电纺膜的增强剂。研究中使用拉伸实验研究TOCNs的增强作用,此外还使用扫描电子显微镜、红外光谱仪、热重分析仪及差示扫描量热仪等对静电纺膜进行结构性能表征。扫描电镜观察发现当纳米纤维素加入量为5%(质量分数)时,其在聚合物基质中分散良好,所得静电纺纳米纤维保持了良好的形态。此外,加入5%(质量分数)的纳米纤维素能够将材料的抗张强度提高44%,且纳米纤维素的加入对材料的热稳定性也有一定的改善,纳米纤维素起到一种纳米填料的效果。鉴于PVA、WPU、TOCNs均为亲水性,无毒且具有生物相容性的物质,所得静电纺膜在组织支架及伤口护理材料等方面具有潜在应用。     

Controlled lowering of graphitization temperature of electrospun poly(acrylonitrile) based carbon fiber by carbon nanotube embedment

Structural evolution of electrospun poly(acrylonitrile) based carbon fibers embedded with multi-wall carbon nanotube (MWCNT) by heat treatment between 1000 and 3000 °C is reported. The graphitization of the fibers is seen to be enhanced in the presence of MWCNT. Graphite fibers with high crystallinity and with a lattice constant nearly equal to that of highly oriented pyrolytic graphite can be prepared at a temperature of 2000 °C, with a small percentage (∼ 5 wt.%) of MWCNT embedded into it. This is a reduction of the graphitization temperature by ∼ 1000 °C from the conventional graphitization temperature of ∼ 3000 °C without the addition of any metallic catalyst.     

The release of 5-fluorouracil from microspheres of poly(epsilon-caprolactone-co-ethylene oxide)

The purpose of this study was to evaluate the in vitro release of 5-fluorouracil from microspheres prepared using a novel triblock copolymer of ε-caprolactone and ethylene oxide as the encapsulating material. Microspheres of poly(ε-caprolactone-co-ethylene oxide) were prepared by employing the “hot-melt” method of microencapsulation. Microspheres were sized using sieve analysis and scanning electron microscopy (SEM). Release studies were performed using a custom-made rotating paddle dissolution apparatus. Copolymer microspheres, fabricated by the hot melt method were shown by electron microscopy to have smooth, nonporous surfaces. Drug-loaded microspheres were found to have a broad distribution of sizes, which was thought to be a consequence of the wide range of crystal sizes of the encapsulated unmilled drug. Nonlinear release kinetics were observed from microspheres in the size fraction 75-250 μm, with a pronounced “burst release” associated with the presence of drug at the surface of the microspheres. A specific delineation of the drug release mechanism was not possible due to rapid gelation, swelling, and subsequent dissolution of the microspheres that occurred on hydration. This work describes the preparation of microspheres that swell rapidly and coalesce together on hydration, accompanied by rapid drug release and copolymer dissolution over a 2-hr period.     

Comparison of two polymeric carrier formulations for controlled release of hydrophilic and hydrophobic drugs

Two temperature sensitive drug carriers, poly (N-isopropylacrylamide-co-acrylic acid) (PNIPA-co-AA) and poly (N-isopropylacrylamide-vinyl pyrrolidone-acrylic acid) (PNIPA-VP-AA), were successfully synthesized through free radical mechanism. The diameters of PNIPA-co-AA and PNIPA-VP-AA particles can be regulated to be less than 100 nm, which were related to surfactant sodiumdodecyl sulfate and initiator ferrous ammonium sulfate, respectively. The lower critical solution temperature (LCST) of them can be manipulated to be higher than 40 °C, which was correlated to amount of acrylic acid (AA) that was copolymerized with NIPA. Hydrophilic anti-tumor drugs, 5-fluorouracil (5-Fu) and hydrophobic drug thalidomide were entrapped into PNIPA-co-AA and PNIPA-VP-AA, respectively. For different interaction mechanism between drug and carrier, 5-Fu was prone to be entrapped in PNIPA-co-AA with loading efficiency larger than 10% (w/w), while thalidomide was entrapped in PNIPA-VP-AA up to 80% (w/w). Fluorescein, an angiography agent, was used to evaluate the drug loading mechanism between PNIPA-VP-AA and poor water-soluble drug. In vitro drug release behavior from these two drug carriers were significantly different and showed temperature dependent, which demonstrated that PNIPA-co-AA and PNIPA-VP-AA are promising candidates for different controlled drug delivery system.     

Poly(vinyl alcohol) hydrogels as hydrophilic matrices for the release of lipophilic drugs loaded in PLGA nanoparticles

Poly(vinyl alcohol) (PVA) hydrogels prepared by a freeze-thawing procedure were evaluated as matrices for the release of water-insoluble drugs such as dexamethasone. As it is impossible to directly entrap a lipophilic drug into a hydrophilic matrix, a novel mechanism has been designed based on producing biodegradable nanoparticles loaded with the drug, that could then be entrapped into the hydrogels. Nanoparticles were prepared by a solvent evaporation technique using a biodegradable copolymer of poly(lactic acid)-poly(glycolic acid) (PLGA). The effects of several processing parameters on particle properties were investigated. The drug release from free nanoparticles was compared to that from the nanoparticles entrapped into the PVA matrices. It was observed that the release profile of the drug is not significantly affected by the PVA matrix. A correlation was found between the amount of drug released and the PVA concentration in the hydrogels: the percentage of drug released, as a function of time, decreased by increasing PVA concentration, indicating that PVA concentration can be used as a tool in modulating the release of the drug.     

Preparation and characterization of chitosan/poly(vinyl alcohol)/poly(vinyl pyrrolidone) electrospun fibers

Ultrafine fibers of chitosan/poly(vinyl alcohol)/poly(vinyl pyrrolidone) (CS/PVA/PVP) were prepared via electrospinning. The structure and morphology of CS/PVA/PVP ultrafine fibers was characterized by the Fourier transform infrared (FT-IR) spectroscope and scanning electron microscope (SEM). Furthermore, the effects of the concentration of PVA, PVP and the electrospinning voltage on the morphology of ultrafine fibers were investigated the the SEM. When the concentration of PVA was at the range of 30wt%–40wt%, ultrafine fibers could be obtained. The diameter distributions of ultrafine fibers decreased when the electrospinning voltage increased from 20 to 30 kV. The rough surface fibers could be obtained after etching with CHCl₃.     

可降解聚碳酸亚丙酯马来酸酯载药微球的制备

采用阴离子配位聚合方法,合成了二氧化碳(CO2),环氧丙烷(PO)与马来酸酐(MA)的三元共聚物,聚碳酸亚丙酯马来酸酯 (PPCMA).采用复相乳液(W/O/W)溶剂挥发法制备了包裹水溶性模型药物葡萄糖(glucose)的可降解微球,并研究了壁材与囊心的比例、稳定剂明胶浓度、搅拌速率等因素对微球性能的影响.当v(PPCMA)∶v(glucose)=1∶2,gelatin质量分数为0.2%,第1次乳化搅拌速率为400r/min,第2次乳化搅拌速率为500r/min时,得到粒径较小、载药量和包封率分别为26.1%和76.1%的载药微球.     

Mineralization of poly(l-lactic acid)-based foams induced by cellulose nanofibrils

Cellulose nanofibrils (CNFs) were blended with poly(l-lactic acid) (PLLA) to produce CNFs/PLLA composite solid foams. The dispersed CNFs’ phase was partially embedded in the PLLA matrix. The CNFs not only reduced the water contact angle of the composite, but also induced the formation of hydroxyapatite (HA) on the walls of its inner pores. After incubation for 7 days in 3× simulated body fluid, a large number of HA particles were formed throughout the CNFs/PLLA composite foams. HA particles have diameters ranging from 200 nm to 2 μm and a Ca/P ratio of 1.42. The spatial distribution of calcium and phosphorus elements was uniform. A porosity of approximately 92 % was achieved after mineralization of the CNFs/PLLA composite foams. The mass of HA grown over CNFs/PLLA foams increased faster than in the case of PLLA foams. The ternary polymeric foams have potential applications in tissue engineering.     

Effect of additives on the interfacial strength of poly(l-lactic acid) and poly(3-hydroxy butyric acid)-flax fibre composites

The interfacial shear strength (IFSS), evaluated by single fibre pull-out tests was quantified for various biopolymer-flax fibre composites that were modified with additives. The additives included a plasticiser (glycerol triacetate) (GTA) absorbed onto/into the fibres, 4,4′-thiodiphenol (TDP) that is capable of forming hydrogen bonds between the matrix and cellulose from the fibres, and a hyperbranched polyester (HBP) to impart improved fracture toughness. Fibres were washed with acetone to remove the surface impurities and dried under vacuum before absorption of plasticiser and adsorption of thiodiphenol. It was found that the different additives significantly influenced the IFSS for the biopolymer-flax fibre systems while extraction with acetone had a no effect on the IFSS compared with the untreated fibres. The use of TDP imparted the most significant increase in IFSS whilst the HBP had an opposing effect. The use of ESEM corroborated with the findings of the single fibre pull-out tests.     

Novel antibacterial electrospun mats based on poly(d,l-lactide) nanofibers and zinc oxide nanoparticles

This investigation addresses the morphological, mechanical, and antibacterial evaluation of nanocomposite mats based on poly(d,l-lactide) nanofibers with different zinc oxide nanoparticles (nano-ZnO) concentration, that were elaborated by two techniques, i.e., electrospinning of polymer/ZnO solutions and the combination of electrospinning of polymer solutions with electrospraying of nano-ZnO dispersions. The analysis of the precursory solutions was carried out in order to understand the achieved morphology of nanofibers. The obtained poly(d,l-lactide)/ZnO fibrous mats showed a uniform morphology with an average porosity ca. 55 % and average pore size around 45 μm. The presence of ZnO nanoparticles increased the toughness of the mats, and an optimal nano-ZnO concentration (i.e., 3 wt%) was observed at which the tensile strength and Young’s modulus could be improved. Concerning to the antibacterial properties, a relatively low concentration of nanoparticles provoked a growth inhibition of the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus bacteria. The mats have potential features for use as antimicrobial wound dressings.