Fabrication,characterization and in vitro drug release behavior of electrospun PLGA/chitosan nanofibrous scaffold

In this study both aligned and randomly oriented poly(d,l-lactide-co-glycolide) (PLGA)/chitosan nanofibrous scaffold have been prepared by electrospinning. The ratio of PLGA to chitosan was adjusted to get smooth nanofiber surface. Morphological characterization using scanning electron microscopy showed that the aligned nanofiber diameter distribution obtained by electrospinning of polymer blend increased with the increase of chitosan content which was similar to that of randomly oriented nanofibers. The release characteristic of model drug fenbufen (FBF) from the FBF-loaded aligned and randomly oriented PLGA and PLGA/chitosan nanofibrous scaffolds was investigated. The drug release rate increased with the increase of chitosan content because the addition of chitosan enhanced the hydrophilicity of the PLGA/chitosan composite scaffold. Moreover, for the aligned PLGA/chitosan nanofibrous scaffold the release rate was lower than that of randomly oriented PLGA/chitosan nanofibrous scaffold, which indicated that the nanofiber arrangement would influence the release behavior. In addition, crosslinking in glutaraldehyde vapor would decrease the burst release of FBF from FBF-loaded PLGA/chitosan nanofibrous scaffold with a PLGA/chitosan ratio less than 9/1, which would be beneficial for drug release.     

Review: the characterization of electrospun nanofibrous liquid filtration membranes

Electrospun nanofibrous membranes (ENMs) are used in a variety of applications, including sensors, tissue engineering, air filtration, energy, and reinforcement in composite materials. Recently, they have gained an interest in the field of liquid filtration. The membranes, surface, bulk, and overall architecture play an important role in the filtration properties and hence the right characterization technique needs to be established, which will pave the way for future developments in the field of filtration. In this article, we have reviewed the recent advances in ENMs for liquid separation application.     

Design and fabrication of imidazolium ion-immobilized electrospun polyurethane membranes with antibacterial activity

By covalently immobilizing imidazolium ion onto molecular chain, functional polyurethane (PU) is fabricated and thus an effective way is initiated to prepare electrospun membranes with antibacterial activity. In the experiment, PUs containing imidazolium ion side group (Bmim-PUs) are synthesized through a two-step polymerization process. It includes prepolymerization of isophorone diisocyanate (IPDI) with polyester glycol and chain extension polymerization using imidazolium-based ionic diol (Bmim-OH). Then, the obtained Bmim-PUs are electrospun into fibrous membranes with a diameter of ~640 nm. After a careful assessment, antibacterial activities of electrospun membranes against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli are clearly exhibited. The antibacterial efficiency of Bmim-PUs on both bacteria species improves by 60% in comparison with PU without imidazolium ion. This research suggests a simple but effective methodology to design and fabricate ultrafine fibrous membrane with significant antibacterial activity. Moreover, the obtained fibrous membranes have widely potential applications in protective textiles, filtration, and biomedical engineering.     

Cellulose acetate nanofibers with photochromic property: Fabrication and characterization

Photochromic nanofibers were fabricated by electrospinning the complex of cellulose acetate (CA)-1′,3′,3′-trimethyl-6-nitrospiro (2H-1-benzopyran-2,2′-indoline) (NO₂SP) and their photochromic properties were investigated. The as-spun nanofibers were characterized by infrared spectra (IR) and the results showed a significant hydrogen bonding reaction between CA and NO₂SP. Incorporated NO₂SP was found to exert no effect on the nanofiber morphology. Through monitoring the color change and the water contact angle of the CA-NO₂SP nanofibrous mat, the reversible photochromic property of the nanofibers was testified. The results of ultraviolet-visible (UV-vis) spectrophotometry and fluorescence microscopy indicated that NO₂SP could endow electrospun fibers with good photochromic and fluorescent properties. Photochromic nanofibers with excellent photosensitivity have great potentials for the applications in optical devices and/or biosensors.     

Cellulose acetate microspheres as floating depot systems to increase gastric retention of antidiabetic drug: formulation, characterization and in vitro-in vivo evaluation

Gastric emptying is a complex process that is highly variable and makes the in vivo performance of drug delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug delivery systems for more than 12 hours utilizing floating or hydrodynamically controlled drug delivery systems. The objective of this investigation was to develop a floating, depot-forming drug delivery system for an antidiabetic drug based on microparticulate technology to maintain constant plasma drug concentrations over a prolonged period of time for effective control of blood sugar levels. Formulations were optimized using cellulose acetate as the polymer and evaluated in vitro for physicochemical characteristics and drug release in phosphate buffered saline (pH 7.4), and evaluated in vivo in healthy male albino mice. The shape and the surface morphology of the prepared microspheres were characterized by optical microscopy and scanning electron microscopy. In vitro drug release studies were performed and drug release kinetics were calculated using the linear regression method. Effects of stirring rate during preparation and polymer concentration on the size of microspheres and drug release were observed. The prepared microspheres exhibited prolonged drug release (more than 10 hours) and remained buoyant for over 10 hours. Spherical and smooth-surfaced microspheres with encapsulation efficiency ranging from 73% to 98% were obtained. The release rate decreased and the mean particle size increased at higher polymer concentrations. Stirring speed affected the morphology of the microspheres. This investigation revealed that upon administration, the biocompatible depot-forming polymeric microspheres controlled the drug release and plasma sugar levels more efficiently than plain orally given drug. These formulations, with their reduced frequency of administration and better control over drug disposition, may provide an economic benefit to the user compared with products currently available for diabetes control.     

Photoconductive optically driven deformable membrane under high-frequency bias: fabrication, characterization, and modeling

The fabrication and characterization of an optically addressable deformable mirror for a spatial light modulator are described. Device operation utilizes an electrostatically driven pixelated aluminized polymeric membrane mirror supported above an optically controlled photoconductive GaAs substrate. A 5 mum thick grid of patterned photoresist supports the 2 mum thick aluminized Mylar membrane. A conductive ZnO layer is placed on the backside of the GaAs wafer. Similar devices were also fabricated with InP. A standard Michelson interferometer is used to measure mirror deformation data as a function of illumination, applied voltage, and frequency. The device operates as an impedance distribution between two cascaded impedances of deformable membrane substrate, substrate, and electrode. An analysis of device's operation under several bias conditions, which relates membrane deformation to operating parameters, is presented.     

Fabrication and characterization of gold nanoparticle-doped electrospun PCL/chitosan nanofibrous scaffolds for nerve tissue engineering

In the field of nerve tissue engineering, nanofibrous scaffolds could be a promising candidate when they are incorporated with electrical cues. Unique physico-chemical properties of gold nanoparticles (AuNPs) make them an appropriate component for increasing the conductivity of scaffolds to enhance the electrical signal transfer between neural cells. The aim of this study was fabrication of AuNPs-doped nanofibrous scaffolds for peripheral nerve tissue engineering. Polycaprolactone (PCL)/chitosan mixtures with different concentrations of chitosan (0.5, 1 and 1.5) were electrospun to obtain nanofibrous scaffolds. AuNPs were synthesized by the reduction of HAuCl₄ using chitosan as a reducing/stabilizing agent. A uniform distribution of AuNPs with spherical shape was achieved throughout the PCL/chitosan matrix. The UV–Vis spectrum revealed that the amount of gold ions absorbed by nanofibrous scaffolds is in direct relationship with their chitosan content. Evaluation of electrical property showed that inclusion of AuNPs significantly enhanced the conductivity of scaffolds. Finally, after 5 days of culture, biological response of Schwann cells on the AuNPs-doped scaffolds was superior to that on as-prepared scaffolds in terms of improved cell attachment and higher proliferation. It can be concluded that the prepared AuNPs-doped scaffolds can be used to promote peripheral nerve regeneration.

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A novel Ag/graphene composite: facile fabrication and enhanced antibacterial properties

In this work, a novel Ag/graphene composite was synthesized as a promising antibacterial agent. The high-quality graphene was prepared from the expandable graphite first and silver nanoparticles (Ag NPs) were then supported on the graphene sheets by a facile chemical reduction. TEM, SEM, and XPS characterizations show the crystalline of Ag NPs with a typical diameter of 45–50 nm are homogeneously decorated onto graphene sheets without aggregation. Furthermore, the antibacterial activity of composite is investigated using the agar well diffusion method. Results reveal the Ag/graphene composites exhibit outstanding and stable antibacterial activity against E. coli due to good dispersibility of Ag NPs and high-quality of graphene substrate.     

Mesoporous bioactive glass as a drug delivery system: fabrication, bactericidal properties and biocompatibility

Implant-associated infection remains a difficult medical problem in orthopaedic surgery. Here, we report on the fabrication of gentamicin-loaded mesoporous bioactive glass (Gent-MBG) for use as a controlled antibiotic delivery system to achieve the sustained release of antibiotics in the local sites of bone defects. The high surface area and mesoporous structure of MBG enable higher drug loading efficiency (79–83 %) than non-mesoporous biological glass (NBG) (18–19 %). Gent-MBG exhibits sustained drug release for more than 6 days, and this controlled release of gentamicin significantly inhibits bacterial adhesion and prevents biofilm formation by S. aureus (ATCC25923) and S. epidermidis (ATCC35984). Biocompatibility tests with human bone marrow stromal cells (hBMSCs) indicate that MBG has better biocompatibility than NBG. Therefore, Gent-MBG can be used as a controlled drug delivery system to prevent and/or treat orthopedic peri-implant infections.     

Characterization and mechanical properties of electrospun cellulose acetate/graphene oxide composite nanofibers

Graphene oxide incorporated cellulose acetate composite nanofibers were prepared via an electrospinning technique. The weight percentage of graphene oxide varied from 0.05 to 1.5 wt.% in the polymer solution. The morphologies and crystal structures of the resultant composite nanofibers were investigated by scanning electron microscopy and X-ray diffraction. The specific interaction was demonstrated by Fourier-transform infrared spectroscopy. Tensile test was performed to measure the mechanical properties of the prepared cellulose acetate/graphene oxide composite nanofibers. 1.5 wt.% cellulose acetate/graphene oxide composite nanofibers showed the highest tensile strength and Young's modulus.     

Effect of POSS content on the electrical,thermal, mechanical,and wetting properties of electrospun polyacrylonitrile (PAN)/POSS nanofibrous mats

Although polyacrylonitrile (PAN) has excellent properties as a precursor of carbon fibre, octa-amic polyhedral oligomeric silsesquioxane (POSS) nanoparticles which are hybrid organic–inorganic materials can be incorporated into PAN to tune up the properties such as the mechanical strength, thermal conductivity, and electronic conductivity for a broad range of potential applications. In this work, PAN with POSS of 1, 3, and 5 wt % based on acrylonitrile weight was prepared by solution polymerisation. The synthesised product was dissolved in dimethyl sulphoxide, followed by electrospinning. After electrospinning, the nanofibrous mats were stabilised at 250 °C for 1 h. The diameter of resulting PAN/POSS nanofibrous mats were less than 1 μm, as confirmed by SEM analysis. The effect of POSS on PAN/POSS nanofibrous mats was studied by SEM, universal testing machine, contact angle measurement, Fourier transform infrared spectroscopy, wide angle X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The usefulness of the PAN/POSS nanofibre composites was realised from the improved electrical, thermal, mechanical, and wetting properties compared to pure PAN.     

Sorption of polycyclic aromatic hydrocarbons on electrospun nanofibrous membranes: sorption kinetics and mechanism

Five types of nanofibrous membranes were prepared by electrospinning poly(?-caprolactone) (PCL), poly(d,l-lactide) (PDLLA), poly(lactide-co-caprolactone) (P(LA/CL)), poly(d,l-lactide-co-glycolide) (PDLGA) and methoxy polyethylene glycol-poly(lactide-co-glycolide) (MPEG-PLGA), respectively. These electrospun nanofibrous membranes (ENFMs) were used to adsorb anthracene (ANT), benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) from aqueous solution, and the sorption kinetics and isotherms of these PAHs on the five ENFMs were investigated. The pseudo-second-order model (PSOM) can well describe the sorption kinetics of the three PAHs on five ENFMs, and the partition-adsorption model (PAM) can interpret the sorption processes of PAHs on the ENFMs. PCL ENFMs, which had the largest surface areas (8.57 m² g⁻¹), exhibited excellent sorption capacity for ANT at over 4112.3 ± 35.5 μg g⁻¹. Moreover, the hydrophobicity and pore volume of ENFMs significantly affected the sorption kinetics and sorption capacity of the PAHs. The main sorption mechanisms of three PAHs on the PDLLA ENFMs included hydrophobic interactions and pore-filling, while those of PCL, P(LA/CL) and PDLGA ENFMs were dominated by the hydrophobic interactions. The sorption mechanisms of MPEG-PLGA ENFMs primarily included pore-filling, hydrogen bonding interactions and hydrophobic interactions. Additionally, π-π bonding interaction was also deduced to be involved in all of ENFMs sorption systems.     

Electrospun cellulose acetate membrane for size separating and antibacterial screening of crude polysaccharides

This study aims to produce electrospun cellulose acetate (CA) membrane as the alternative supporting medium for a separation of crude polysaccharides by electrophoresis and a screening of their antibacterial activity. Among the tested conditions of fabrication, electrospun CA membrane at 57% porosity showed the best separation of each polysaccharide from the standard mixture and the crude extract of Aloe vera via electrophoresis. As compared with the commercial CA membrane, the produced electrospun CA membrane demonstrated more separated spots of polysaccharides. The antibacterial activity of the electrophoretic polysaccharide was also determined against Escherichia coli and Staphylococcus aureus as the inhibition zone after the bacterial culture agar was overlaid on the membrane and incubated for 24 h. The results of this study suggested the potential application of electrospun CA membrane combining with electrophoresis as a simple method for separating crude polysaccharides and screening for their antibacterial activity.Inspec keywords: electrospinning, polymers, antibacterial activity, microorganisms, electrophoresis, biomedical materials, porosityOther keywords: electrospun cellulose acetate membrane, size separating, antibacterial screening, crude polysaccharides, alternative supporting medium, electrophoresis, antibacterial activity, electrospun CA membrane, standard mixture, Aloe vera, electrophoretic polysaccharide, Escherichia coli, Staphylococcus aureus, bacterial culture agar     

Inter-sheet-effect-inspired graphene sensors: design, fabrication and characterization

With their sub-nanometer inter-sheet spacing, few-layer graphenes (FLGs) are alignment-free building blocks for nanosensors based on the inter-sheet effects. In this paper, we have tackled the challenges towards batch fabrication of inter-sheet graphene sensors through controlled layer engineering, edge tailoring and selective electrode fabrication on different atomic layers. An oxygen plasma etching (OPE) technique is developed to remove graphene layer by layer, enabling the batch fabrication of FLGs in a controllable fashion because of the faster speed and readiness of patterning of this process as compared to the conventional mechanical exfoliation. Vapor sensing experiments have shown that 'inter-sheet' sensors possess a higher sensitivity than conventional 'intra-sheet' ones. Vapor sensitivity is improved more than two times in normalized resistance changes by taking the 'inter-sheet' design upon exposure to 0.5% ethanol-nitrogen mixture and 500 Pa water vapor environments, respectively. These remarkable improvements can mainly be attributed to the inter-sheet effects such as electron tunneling, chemical doping, physical insertion and enhanced edge effects. Such effects may result from molecule adsorption/desorption, force/displacement, pressure, surface tension or thermal energy, and can potentially remarkably enrich the applicable transduction mechanisms.     

醋酸纤维素氨基甲酸酯膜材料的制备与表征

利用尿素对醋酸纤维素(CA)进行浸泡预处理,然后移入邻二甲苯惰性体系中进行反应,探讨合成过程中的影响因素,结果表明,预处理过程中尿素的质量分数为25%,预处理温度55℃,预处理时间5 h,反应时间3.5 h时,所得醋酸纤维素氨基甲酸酯(CAC)取代度可达到0.1.FT-IR表征可以证明成功合成出了CAC.用制备的CAC进行铸膜,CAC膜的拉伸强度及水通量要优于CA膜,同时研究得出随着取代度的升高,CAC膜的拉伸强度及水通量呈上升趋势.     

Electrospun emodin polyvinylpyrrolidone blended nanofibrous membrane: a novel medicated biomaterial for drug delivery and accelerated wound healing

In this work, blended nanofibrous membranes were prepared by an electrospinning technique with polyvinylpyrrolidone (PVP) K90 as the filament-forming polymer, and emodin, an extract of polygonum cuspidate known as a medicinal plant, as the treatment drug. Detailed analysis of the blended nanofibrous membrane by scanning electron microscopy, Differential scanning calorimetry and X-ray diffraction revealed that emodin was well distributed in the ultrafine fibers in the form of amorphous nanosolid dispersions. Results from attenuated total reflectance Fourier transform infrared spectra suggested that the main interactions between PVP and emodin might be mediated through hydrogen bonding. In vitro dissolution tests proved that the blended nanofibrous membrane produced more desired release kinetics of the entrapped drug (emodin) as compared to the pure drug. Furthermore, wound healing test and histological evaluation revealed that the emodin loaded nanofibrous membrane to be more effective as a healing accelerator thereby proving potential strategies to develop composite drug delivery system as well as promising materials for future therapeutic biomedical applications.     

Preparation,characterization and release of amoxicillin from cellulose acetate and poly(vinyl pyrrolidone) coaxial electrospun fibrous membranes

Electrospinning is a method that has been used to prepare polymeric fibers, with diameters ranging from nanometers to a micrometer of polymers such as cellulose acetate (CA) and poly(vinyl pyrrolidone) (PVP), and to develop membranes with applications in microencapsulation, for controlled release of drugs and for chemical and biological sensors. This work shows the feasibility and optimal conditions for the preparation of fibrous composite membranes of cellulose acetate and poly(vinyl pyrrolidone), via electrospinning, and their morphology; FTIR, and mechanical characterization and the effect of pH on the release of amoxicillin were analyzed. Tubes of CA with diameters around 500 nm were obtained. It was found that the release behavior of the drug from these fibrous membranes was dependent on the pH of the medium. It was observed that the amount of amoxicillin released as a function of time for a pH equal to 7.2 was approximately three times higher than that observed for a pH equal to 3.0. This suggests a greater interaction of amoxicillin with components of the membrane at a pH equal to 3.0, most likely due to the formation of hydrogen bonds. These materials have potential application in gastrointestinal administration and for transdermal patches.