Cellulose acetate electrospun fiber mats for controlled release of silymarin

In this research, the silymarin-loaded electrospun cellulose acetate (CA) fibers were prepared which containing silymarin in various amounts (i.e., 2.5-20 wt.% based on the weight of CA powder). Incorporation of silymarin in the neat CA solution did not affect the morphology of the resulting fibers, as both the neat and the silymarin-loaded CA fibers were smooth. The average diameters of silymarin-loaded CA fiber ranged between 550-900 nm. No presence of the silymarin aggregates of any kind was observed on the surfaces of these fibers, suggesting that the silymarin was encapsulated well within the fibers. These results were confirmed by lowering the glass transition temperature and the melting temperature of the silymarin-loaded electrospun CA fibers which is determined by DSC technique. The release characteristic of silymarin from the silymarin-loaded CA fiber mats was investigated by the total immersion in the solution of 1/1 phosphate buffer/methanol medium pH 7.4 at 37 degrees C. The silymarin release from the silymarin-loaded electrospun CA fiber mat is monotonously increased to reach the maximum value at 480 min. The maximum amount of silymarin released from these materials increases with the increasing of initial silymarin loading in the spinning CA solutions. Since no aggregation of silymarin was found on the surface of the silymarin-loaded fibers, the release of the silymarin from fiber mats was mainly by the diffusion.     

Compressibility of electrospun fiber mats

Compressive properties of electrospun fiber mats are reported for the first time. Mats of bisphenol-A polysulfone (PSU) and of poly(trimethyl hexamethylene terephthalamide) [PA 6(3)T] were electrospun and annealed over a range of temperatures spanning the glass transition temperature of each polymer. The data for applied stress versus mat solidity were found to be well-described by a power law of the form $ \sigma_{\text{zz}} = kE\left( {\phi^{n} - \phi_{0}^{n} } \right) $ σ zz = kE ( ? n ? ? 0 n ) , where $ \sigma_{\text{zz}} $ σ zz is the applied stress and ? is solidity, in accord with the analysis of Toll (Polym Eng Sci 38(8):1337, 2004). The values of n range from 3.2 to 6 for PSU and from 8.0 to 20 for PA 6(3)T. The lowest values in each case were exhibited by mats annealed near the glass transition temperature of the fiber material. The values of n are independent of fiber diameter. The higher values of n are attributed to fiber slippage via a mechanism analogous to that of work hardening of metals. The values of kE can vary by an order of magnitude and were difficult to determine precisely, due to the nature of the power law and the inhomogeneity of the mats. The compressibility of electrospun mats in response to an applied stress is sufficiently large that it cannot be neglected in applications where large pressures may be involved, such as filtration or membrane separations. In addition to the initial solidity of the mats, the material compressibility and the operating pressure relevant to the application are important to describe the structure of electrospun mats quantitatively under conditions of use.     

掺CCCW的碳纤维石墨水泥基复合材料的导电及压阻特性

利用四电极法研究了内掺水泥基渗透结晶防水材料(CCCW)的碳纤维石墨水泥基复合材料试样(40 mm×40 mm×40 mm)的导电特性及其在循环荷载作用下的压阻特性,分析讨论了碳纤维石墨水泥砂浆的体积电阻率及压阻特性随石墨掺量的变化规律。碳纤维和CCCW的掺量分别为水泥质量的1%和4%;石墨掺量分别为水泥质量的0%、10%、20%、30%、40%和50%。结果表明,添加CCCW的碳纤维石墨砂浆试样的体积电阻率随石墨掺量的增加迅速下降,并存在渗滤现象,渗滤阈值为20%左右。在循环荷载作用下,不同石墨掺量试样的电阻和应力存在一定的对应关系。石墨掺量为水泥质量的20%～30%时,碳纤维石墨水泥砂浆试样的体积电阻率与压应力呈现良好的可重复性,电阻值在应力加载时几乎呈线性下降,而卸载时增加。     

Prolonged release from PLGA/HAp scaffolds containing drug-loaded PLGA/gelatin composite microspheres

Porous scaffolds that can prolong the release of bioactive factors are urgently required in bone tissue engineering. In this study, PLGA/gelatin composite microspheres (PGMs) were carefully designed and prepared by entrapping poly(l-lactide-co-glycolide) (PLGA) microspheres (PMs) in gelatin matrix. By mixing PGMs with PLGA solution directly, drug-loaded PLGA/carbonated hydroxyapatite (HAp)/PGMs composite scaffolds were successfully fabricated. In vitro release of fluorescein isothiocyanate-dextran (FD70S) as a model drug from the scaffolds as well as PMs and PGMs was studied by immersing samples in phosphate buffered saline (pH = 7.4) at 37°C for 32 days. Compared with PMs, PGMs and PLGA/HAp/PGMs scaffolds exhibited slow and steady release behavior with constant release rate and insignificantly original burst release. The swelling of PGMs, diffusion of drugs, and degradation of polymer dominated the release behaviors synergistically. The PLGA/HAp/PGMs scaffold offers a novel option for sequential or simultaneous release of several drugs in terms of bone regeneration.     

Hybrid multi-scale epoxy composite made of conventional carbon fiber fabrics with interlaminar regions containing electrospun carbon nanofiber mats

Herein we report the development and evaluation of hybrid multi-scale epoxy composite made of conventional carbon fiber fabrics with interlaminar regions containing mats of electrospun carbon nanofibers (ECNs). The results indicated that (1) the interlaminar shear strength and flexural properties of hybrid multi-scale composite were substantially higher than those of control/comparison composite without ECNs; in particular, the interlaminar shear strength was higher by ∼86%; and (2) the electrical conductivities in both in-plane and out-of-plane directions were enhanced through incorporation of ECNs, while the enhancement of out-of-plane conductivity (∼150%) was much larger than that of in-plane conductivity (∼20%). To validate the data reduction procedure, a new shear stress formula was formulated for composite laminates, which took into account the effect of layup and inter-layers. The study suggested that ECNs could be utilized for the development of high-performance composites, particularly with the improved out-of-plan properties (e.g., interlaminar shear strength).     

Preparation and photocatalytic activity of nanoporous zirconia electrospun fiber mats

Nanoporous zirconia electrospun fiber mats (NZEFM) have been prepared by an electrospinning process using nonionic F108 as a pore-forming agent. This nonaqueous synthesis route has been employed to fabricate a stable “building block” porous structure inside the nano-scale fibers. The mats composed of individual fibers proved to be robust after calcination at up to 450 °C or stirring in water. The photocatalytic activity of NZEFM is apparently higher than that of commercial zirconia powder for the degradation of methyl orange in aqueous solution. Moreover, amorphous NZEFM mixed with the tetragonal phase obtained at 450 °C proved to be more efficient than the monoclinic phase NZEFM obtained at 900 °C. Various dyes could be degraded by NZEFM under UV light irradiation. The highly photocatalytic activity of NZEFM could be attributed to its high specific surface area and nanoporous “building block” structure made up of stacked zirconia nanoparticles.     

Controlled dual release of hydrophobic and hydrophilic drugs from electrospun poly(l-lactic acid) fiber mats loaded with chitosan microspheres

This work is to develop novel electrospun poly(l-lactic acid) (PLLA) fiber mats for controllable delivery of hydrophobic and hydrophilic drugs. For this aim, bovine serum albumin (BSA, used as a hydrophilic model drug) was firstly enveloped into chitosan microspheres by spray drying. Benzoin (used as a hydrophobic model drug) was directly dissolved in PLLA solution and then the chitosan microspheres were suspended into the PLLA solution, which was used to prepare PLLA fiber mats by electrospinning. Polyvinylpyrrolidone (PVP) was added into the PLLA solution to tune the drug release behaviors. The results showed that the chitosan microspheres were uniformly distributed in the fibers. BSA had a short-term release while benzoin had a long-term and sustained release in all the dual drug delivery systems, and the release of both hydrophobic and hydrophilic drugs could be adjusted by changing the ratio of PVP/PLLA.     

Fabrication and morphological study of converged SiC-TiC fiber mats by electrospinning

Titanium-containing silicon carbide (SiC) fiber mats were fabricated by an electrospinning method followed with a polymer-derived ceramics route. Titanium isopropoxide was used to cross-link into polycarbosilane (PCS) in toluene and xylene contained in the medium. The mat structure, fiber morphology, and crystallization of the fabricated SiC fibrous mat were analyzed by scanning electron microscopy and X-ray diffraction. According to the analysis results, the ceramic yield of the precursor increased significantly because of the high degree of cross-linking in PCS molecular structure.     

磁性明胶载药微球的制备及体外释药研究

以诺氟沙星为水溶性模型药物,采用反相悬液冷冻凝聚法制得包裹Fe3O4微粒和药物的磁性明胶微球,考察了磁性载药微球的制备条件对微球的成球率、药物包裹率、体外释药及微球降解情况的影响.结果表明,明胶的浓度、戊二醛的用量、固化时间等均对微球的结构和性能产生影响,经优化条件得到了成球率、药物包裹率、体外释放都较好的载药微球.     

Phosphate salts facilitate the electrospinning of hyaluronic acid fiber mats

Electrospinning is a cost effective and facile method to manufacture fiber mats appropriate for biomedical applications. Due to its high molecular weight and charged backbone, hyaluronic acid (HA) fiber mats with consistent fiber morphology have been difficult to electrospin from neutral pH solutions. Here, we present that the electrospinning of HA fibers in aqueous dimethylformamide solutions is facilitated by the addition of three phosphate salts. The salts—glycerol phosphate (GP), sodium phosphate (SP), and tripolyphosphate (TPP)—facilitated electrospinning of the solutions as characterized by conductivity measurements and fiber morphology. From tensile experiments, HA mats electrospun with SP demonstrated improved Young’s modulus (12 MPa) over HA mats spun with either GP or TPP (5 and 3 MPa, respectively). This work demonstrates that a new neutral solvent system can be employed to spin HA fibers, which offers the potential for using the fibers for biomedical applications, such as a bone biomimetic.     

Electrospun polylactic acid and cassava starch fiber by conjugated solvent technique

Smoothed fibers of PLA/cassava starch were prepared by single nozzle electrospinning process intended for tissue scaffold application. PLA in dichloromethane (DCM) solution was immiscible with cassava starch in dimethylsulfoxide (DMSO) solution. A conjugated solvent system was introduced to simply prepare a well-mixed solution of both components. In this experiment, methanol was used as a conjugated solvent between PLA/DCM solution and cassava starch/DMSO solution to create well-mixed solution. Conjugated solvent selection was based on values of polarity index, intermediate between values of DCM and DMSO. Smoothed electrospun fiber of PLA/cassava starch was obtained.     

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.     

Properties of anti-washout-type calcium silicate bone cements containing gelatin

Novel washout-resistant bone substitute materials consisting of gelatin-containing calcium silicate cements (CSCs) were developed. The washout resistance, setting time, diametral tensile strength (DTS), morphology, and phase composition of the hybrid cements were evaluated. The results indicated that the dominant phase of β-Ca₂SiO₄ for the SiO₂–CaO powders increased with an increase in the CaO content of the sols. After mixing with water, the setting times of the CSCs ranged from 10 to 29 min, increasing with a decrease in the amount of CaO in the sols. Addition of gelatin into the CSC significantly prolonged (P < 0.05) the setting time by about 2 and 8 times, respectively, for 5% and 10% gelatin. However, the presence of gelatin appreciably improved the anti-washout and brittle properties of the cements without adversely affecting mechanical strength. It was concluded that 5% gelatin-containing CSC may be useful as bioactive bone repair materials.     

Stability study of hard gelatin capsules containing retinoic acid

Retinoic acid (RA) is employed in the therapeutic treatment of acute promyelocytic leukemia (APL). In this paper, the chemical stability and the most favorable storage conditions of RA in hard gelatin capsules containing alpha-lactose monohydrate, used in clinical experimentation, are reported. A secondary goal of this work was to show the usefulness of a robust regression technique, repeated median with replicates (RMWR) in a solid-state shelf life prediction by accelerated studies. The capsules were stored at room temperature and in the freezer. Their residual RA content was assayed for more than 3 years. RA chemical degradation was monitored by high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) stability-indicating methods previously validated and able to detect various potential degradation products. Possible physical modifications were checked by dissolution tests and differential scanning calorimetry (DSC) of the content of the capsules. The shelf life was also predicted by an accelerated isothermal method to confirm room temperature results, and the activation energy estimated through this study was 12.5 +/- 1.1 kcal/mol (95% confidence interval). In the conditions of climatic zone II, the shelf life for the capsules stored at room temperature in light-resistant containers was equal to 678 days, while the capsules stored in the freezer retained the initial content of drug after 1289 days. From the results gathered in this study, the usefulness of RMWR for shelf life prediction in the presence of outliers is evident.     

Mechanical and degradation characteristics of natural silk fiber reinforced gelatin composites

Silk reinforced gelatin based composites were prepared by compression molding. The fiber content in the composite was 20 wt.%. Tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM), impact strength (IS) and hardness of the composites were found 44.5 MPa, 0.65 GPa, 63 MPa, 3.7 GPa, 5.1 kJ/m² and 96 shore A respectively. The environmental effect on composite was observed by simulating weathering test and the composite lost 15.2% TS at the end of 30 h of the weathering testing period. The biodegradation test shows that the composite degrades very quickly and losses 52.1% weight at the end of 24 h. Morphological analysis was carried out to observe fracture behaviour and fiber pullout of the samples.     

Electrospun fiber template for replica molding of microtopographical neural growth guidance

A method for replica molding electrospun (ES) fibers on the surface of polydimethylsiloxane (PDMS) is developed for culturing and guiding of cells, instead of ES fibers. With this method, microgrooves and microstructures composed of microgrooves can be obtained. PDMS is integrated into the microfluidic chip as a substrate to successfully pattern and guide neurites on the PDMS surface with microgrooves.     

Microstructure and characteristic properties of gelatin/chitosan scaffold prepared by a combined freeze-drying/leaching method

A combined freeze-drying and particulate leaching method for scaffold synthesis showed an improvement in the horizontal microstructure of the gelatin/chitosan scaffolds. Type and concentration of the cross-linking agent, freezing temperature, concentration of the polymeric solution and gelatin/chitosan weight ratio were the variables affecting the scaffold properties. Assessment of the tensile properties of the scaffolds revealed that for a scaffold with 50% chitosan, glutaraldehyde, as a cross-linking agent, created much tighter polymeric network compared to N,N-(3-dimethylaminopropyl)-N′-ethyl carbodiimide (EDC). However, in the case of gelatin scaffolds, EDC was identified as the stronger cross-linker. Compressive behavior of the scaffolds satisfied formulations obtained from the theoretical modeling of the low-density, elastomeric foams. The investigation of the scaffold degradation indicated that the increase in the mechanical strength of the scaffolds would not always reduce their degradation rate.     

Design and in vitro evaluation of transdermal patches based on ibuprofen-loaded electrospun fiber mats

To improve the poor compatibility among different components of Drug-in-adhesive type patch, two novel plasters (Drug-in-fiber and Drug-in-adhesive/fiber) were developed based on ibuprofen (IBU)-loaded fiber mats. These fibrous mats were fabricated via electrospinning of cellulose acetate/poly(vinylpyrrolidone) composites in a binary solvent of N,N-dimethyl acetamide/acetone. Physical status studies suggested that Drug-in-fiber could inhibit IBU re-crystallization, but the active ingredients were released at a relatively slow rate due to the dual-resistance of fiber mat and adhesive matrix. To overcome this shortcoming, Drug-in-adhesive/fiber was designed by coupling medicated hydrophilic pressure sensitive adhesive and IBU-loaded fiber mat. This method endowed Drug-in-adhesive/fiber a fast IBU release rate and high permeated drug amount though simulative skins. This design separated enhancer from adhesive matrix, which guaranteed Drug-in-adhesive/fiber excellent adhesion forces. Hence, the plasters based on medicated fiber mats improved the compatibility among patch components.     

Preparation and antimicrobial activity of gelatin microparticles containing propolis against oral pathogens

Gelatin microparticles containing propolis ethanolic extractive solution were prepared by spray-drying technique. Particles with regular morphology, mean diameter ranging of 2.27 μm to 2.48 μm, and good entrapment efficiency for propolis were obtained. The in vitro antimicrobial activity of microparticles was evaluated against microorganisms of oral importance (Enterococcus faecalis, Streptococcus salivarius, Streptococcus sanguinis, Streptococcus mitis, Streptococcus mutans, Streptococcus sobrinus, Candida albicans, and Lactobacillus casei). The utilized techniques were diffusion in agar and determination of minimum inhibitory concentration. The choice of the method to evaluate the antimicrobial activity of microparticles showed be very important. The microparticles displayed activity against all tested strains of similar way to the propolis, showing greater activity against the strains of E. salivarius, S. sanguinis, S. mitis, and C. albicans.