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Novel adsorbents with a simple preparation process and large capacity for removing highly toxic and nondegradable heavy metals from water have drawn the attention of researchers. Electrospun nanofiber membranes usually have the advantages of large specific surface areas and high porosity and allowing flexible control and easy functionalization. These membranes show remarkable application potential in the field of heavy metal wastewater treatment. In this paper, the electrospinning technologies, process types, and the structures and types of nanofibers that can be prepared are reviewed, and the relationships among process, structure and properties are discussed. On one hand, based on the different components of electrospun nanofibers, the use of organic, inorganic and organic-inorganic nanofiber membrane adsorbents in heavy metal wastewater treatment are introduced, and their advantages and future development are summarized and prospected. On the other hand, based on the microstructure and overall structure of the nanofiber membrane, the recent progresses of electrospun functional membranes for heavy metal removal are reviewed, and the advantages of different structures for applications are concluded. Overall, this study lays the foundation for future research aiming to provide more novel structured adsorbents. [ABSTRACT FROM AUTHOR]

The design of stable, efficient and processable bactericidal materials represents a significant challenge for combating multidrug-resistant bacteria in a variety of engineering fields. Herein, we report a facile strategy for the preparation of hollow polymeric nanosphere (HPN)-supported imidazolium-based ionic liquids (denoted as HPN-ILs) with superior antimicrobial activities. HPN-ILs were tailored by moderate Friedel-Crafts polymerization followed by the sequential covalent bonding of imidazole and bromoalkene. The resultant HPN-ILs have uniform hollow spherical morphology, an adequate surface area, and excellent physicochemical stability. Furthermore, they are highly active against both Gram-positive and Gram-negative bacteria and exhibit typical time/dosage-dependent antibacterial activities. The rational combination of porous HPNs and antibacterial ILs to generate an all-in-one entity may open new avenues for the design and fabrication of efficient bacteriostatic agents. Moreover, HPN-ILs have good biocompatibility and can also be loaded onto diverse matrices, and thus could extend their practical bactericidal application in the potential biomedical-active field. [ABSTRACT FROM AUTHOR]

A solution treated by electrospraying often has a relatively low polymer concentration, thereby overlooking that pure solvent can be used as an additional working fluid. In this study, a modified coaxial electrospraying, characterized by the usage of pure solvent as a shell fluid, was developed to generate nano drug delivery systems for providing the desired drug sustained-release profiles. Ethylcellulose (EC) and tamoxifen citrate (TC) were exploited as a polymer matrix and a poorly water-soluble anticancer model, respectively. Comparing with those particles prepared using a traditional single-fluid process, the TC-loaded EC particles from the modified coaxial processes have a rounder shape, a smaller diameter, and a highly compact inner structure, as demonstrated by the scanning electron microscopic images. Given the favored secondary interactions between TC and EC, all the particles are similarly amorphous composites, as verified by their X-ray patterns and attenuated total reflectance-Fourier transform infrared spectra. Nevertheless, the rounder nanoparticles from the coaxial processes were able to provide a better drug sustained-release profile than their counterparts in terms of smaller initial burst release, longer release time period, and shorter time tailing-off later stage. Both microformation mechanisms of the medicated particles and drug sustained-release mechanisms are suggested. The protocols developed here facilitate the generation of functional nanomaterials from cellulose and its derivatives owing to breaking the traditional concept of electrospraying. [ABSTRACT FROM AUTHOR]

This work is a proof of concept study establishing the potential of electrosprayed Janus particles for combined photodynamic therapy-chemotherapy. Sub-micron-sized particles of polyvinylpyrrolidone containing either an anti-cancer drug (carmofur) or a photosensitiser (rose bengal; RB), and Janus particles containing both in separate compartments were prepared. The functional components were present in the amorphous form in all the particles, and infrared spectroscopy indicated that intermolecular interactions formed between the different species. In vitro drug release studies showed that both carmofur and RB were released at approximately the same rate, with dissolution complete after around 250 min. Cytotoxicity studies were undertaken on model human dermal fibroblasts (HDF) and lung cancer (A549) cells, and the influence of light on cell death explored. Formulations containing carmofur as the sole active ingredient were highly toxic to both cell lines, with or without a light treatment. The RB formulations were non-toxic to HDF when no light was applied, and with photo-treatment caused large amounts of cell death for both A549 and HDF cells. The Janus formulation containing both RB and carmofur was non-toxic to HDF without light, and only slightly toxic with the photo-treatment. In contrast, it was hugely toxic to A549 cells when light was applied. The Janus particles are thus highly selective for cancer cells, and it is hence proposed that such electrosprayed particles containing both a chemotherapeutic agent and photosensitiser have great potential in combined chemotherapy/photodynamic therapy. [ABSTRACT FROM AUTHOR]

Temperature is an important parameter during electrospinning, and virtually, all solution electrospinning processes are conducted at ambient temperature. Nanofiber diameters presumably decrease with the elevation of working fluid temperature. The present study investigated the influence of temperature variations on the formation of polymeric nanofibers during single-fluid electrospinning. The surface tension and viscosity of the fluid decreased with increasing working temperature, which led to the formation of high-quality nanofibers. However, the increase in temperature accelerated the evaporation of the solvent and thus terminated the drawing processes prematurely. A balance can be found between the positive and negative influences of temperature elevation. With polyacrylonitrile (PAN, with N, N-dimethylacetamide as the solvent) and polyvinylpyrrolidone (PVP, with ethanol as the solvent) as the polymeric models, relationships between the working temperature ( T, K) and nanofiber diameter ( D, nm) were established, with D = 12598.6 − 72.9 T + 0.11 T ( R = 0.9988) for PAN fibers and D = 107003.4 − 682.4 T + 1.1 T ( R = 0.9997) for PVP nanofibers. Given the fact that numerous polymers are sensitive to temperature and numerous functional ingredients exhibit temperature-dependent solubility, the present work serves as a valuable reference for creating novel functional nanoproducts by using the elevated temperature electrospinning process. [ABSTRACT FROM AUTHOR]

The present study reports a new type of sedative nanofiber membranes that were developed to permit very rapid oral delivery of helicid with concomitant taste masking. A coaxial electrospinning process was exploited to prepare core-shell nanofibers and to control the spatial depositions of different functional components. A series of tests was undertaken to characterize the resultant nanofibers. Following optimization of the electrospinning parameters, two types of core-shell nanofibers with average diameters of 730 ± 140 and 770 ± 160 nm were successfully prepared. These had uniform linear morphologies and clear core-shell structures, as verified by scanning and transmission electron microscopy images. The fibers contained sucralose in the shell and helicid in the core; X-ray diffraction demonstrated that both functional components were present in the amorphous physical form. There is significant hydrogen bonding between the functional components and the poly(vinylpyrrolidone) used as the carrier matrix, as shown from Fourier transform infrared spectroscopy and molecular mechanics simulations. In vitro dissolution tests showed that the formulations were able to release the entire incorporated drug extremely rapidly (within 1 min) when they encountered a dissolution medium, whereas the commercially available product released only 13.4 % of its drug loading in the same time. By tailoring the distribution of functional ingredients in electrospun core-shell structures, new drug delivery systems which can both accelerate dissolution and also mask unpleasant tastes were produced. [ABSTRACT FROM AUTHOR]

This manuscript reports a new type of drug-loaded core-shell nanofibers that provide tunable biphasic release of quercetin. The nanofibers were fabricated using a modified coaxial electrospinning process, in which a polyvinyl chloride (PVC)-coated concentric spinneret was employed. Poly (vinyl pyrrolidone) (PVP) and ethyl cellulose (EC) were used as the polymer matrices to form the shell and core parts of the nanofibers, respectively. Scanning and transmission electron microscopy demonstrated that the nanofibers had linear morphologies and core-shell structures. The quercetin was found to be present in the nanofibers in the amorphous physical status, on the basis of X-ray diffraction results. In vitro release profiles showed that the PVP shell very rapidly freed its drug cargo into the solution, while the EC core provided the succedent sustained release. Variation of the drug loading permitted the release profiles to be tuned. [ABSTRACT FROM AUTHOR]

Coaxial electrospraying was explored to organize polymer excipients in a core-shell manner for providing biphasic controlled release of active ingredient. With ferulic acid (FA) as a model drug, and shellac and polyvinylpyrrolidone (PVP) as the core and shell polymeric matrices, core-shell nanoparticles were successfully fabricated. A series of tests were carried out to characterize the prepared core-shell nanoparticles and also the nanoparticles prepared using a single fluid electrospraying of the shell or core fluids alone. The core-shell nanoparticles had an average diameter of 530 ± 80 nm with clear core-shell structure. The contained FA was converted to an amorphous state both in the core and the shell parts due to the favorable hydrogen bonding between the components. In vitro dissolution tests demonstrated that the core-shell nanoparticles were able to provide the desired biphasic drug-controlled release profiles. Coaxial electrospraying is a useful tool for the development of novel nanodrug delivery systems from polymers. [ABSTRACT FROM AUTHOR]

Two drawbacks of the traditional electrospinning process when used for producing nanofibers for drug release are that clogging of the spinneret is often experienced, and the fibers produced often exhibit a tailing-off of drug release over sustained periods. The present study investigates the preparation of ferulic acid (FA) sustained-release cellulose acetate (CA) nanofibers, in which a third component, polyvinylpyrrolidone (PVP), was included into the nanocomposites for an improved sustained drug release profile. A modified coaxial electrospinning process, in which only organic solvent N, N-dimethylacetamide was used as a sheath fluid, was exploited for a smooth and continuous fabrication of multiple-component nanofibers. Under an applied voltage of 16 kV and an optimized sheath-to-core flow rate ratio of 0.11, three types of FA/PVP/CA composite nanofibers (with varied of PVP content) were generated. These nanofibers had higher quality in terms of size and distribution of nanofiber diameter, as indicated by FESEM images. Analysis of double- and triple-component nanofibers by XRD, DSC, and ATR-FTIR confirmed the compatibility of components producing homogenous fibers in both cases, but the triple-component nanofibers exhibited better release profiles over sustained periods than the double-component nanofibers in terms of release completeness, reduced tailing-off, and adjustable release rates. The modified coaxial process and the resulting multiple-component nanocomposites should provide a new way for developing novel drug sustained materials and drug delivery systems. [ABSTRACT FROM AUTHOR]

Hydrophobic polyvinylpyrrolidone (PVP) nanofibers, which is intensely hygroscopic, has been successfully prepared to improve their moisture resistance using a modified coaxial electrospinning process. A stearic acid (SA) solution was exploited as the sheath fluid to coat the fibers. Scanning electron microscopy demonstrated that the SA-coated PVP nanofibers became increasingly small with a rise in the sheath-to-core flow rate ratio; continuing to increase the sheath flow rate beyond a cut-off point resulted in nanofibres with very complicated morphologies. Transmission electron microscope images showed that SA formed a thin layer on the PVP nanofibers, with SA nanoparticles present on the fiber surfaces when a sheath-to-core flow rate ratio of 0.2:0.8 was used. Attenuated total reflectance-Fourier transform infrared spectroscopy verified the coating of SA onto the PVP nanofibers, and also the formation of hydrogen bonds between the SA and PVP molecules. The SA-coated PVP nanofibers were found to have much enhanced moisture resistance over pure PVP fibers. Modified coaxial electrospinning hence comprises a novel and powerful strategy for nanocoating and surface modification of polymer nanofibers. [ABSTRACT FROM AUTHOR]

Novel drug-loaded cellulose acetate (CA) nanofibres were prepared by a modified coaxial electrospinning process, after which their zero-order drug release profiles were determined. Using 2 % (w/v) unspinnable CA solution as a sheath fluid, coaxial electrospinning can be conducted smoothly to generate ketoprofen (KET)-loaded CA nanofibres coated with a thin layer of blank CA. Scanning electron microscopy images demonstrated that nanofibres obtained from the modified coaxial process have a smaller average diameter, a narrower size distribution, more uniform structures, and smoother surface morphologies than those generated from single-fluid electrospinning. Transmission electron microscopy observations demonstrated that the nanofibres have a thin coating layer of blank CA on their surface with a thickness of ca. 15 nm. X-ray diffraction and differential scanning calorimetry verified that KET molecules in all of the nanofibres presented an amorphous state. Fourier transform infrared spectra demonstrated that CA has good compatibility with KET, which is brought about by hydrogen bonding. In vitro dissolution tests showed that the nanofibres coated with blank CA have no initial burst release effects and can provide a zero-order drug release profile over 96 h via a diffusion mechanism. The modified coaxial electrospinning method can provide new approaches in developing cellulose-based nano products with definite structural characteristics and improved functional performance. [ABSTRACT FROM AUTHOR]

The present research investigates a modified coaxial process for smoothening electrospinning of cellulose acetate (CA) and obtaining its nanofibers with high quality. With 11 w/v% CA in mixed solvent of acetone and N,N-dimethylacetamide (DMAc) (v:v, 3:1) as electrospinnable core fluid, different solvents (acetone, DMAc and their mixture) are taken as sheath fluids to conduct the modified process. SEM observations demonstrate that the modified process is effective in retarding the clogging of spinneret for a smooth electrospinning and in obtaining high quality CA nanofibers in terms of structural uniformity, diameters, and their distributions. The mechanism about the influence of sheath fluid on the process and the formation of nanofibers is discussed. The key for the modified coaxial process is the reasonable selection of sheath fluids and a sheath-to-core flow rate ratio matching the drawing process of core CA fluid during the electrospinning. The present paper provides a simple method to implement the modified coaxial process for smoothening the electrospinning and obtaining polymer nanofibers with high quality. [ABSTRACT FROM AUTHOR]

Two different electrospinning processes (traditional single fluid one and a modified coaxial electrospinning with organic solvent as sheath fluid) are investigated in relation to their capability of producing thinner nanofibers. Both the modified coaxial electrospinning and single fluid electrospinning can produce thinner nanofibers with polyvinylpyrrolidone (PVP) as a polymer model and using a poor volatile solvent N, N-dimethylacetamide (DMAc) in different ways. However the traditional single fluid process was less effective compared to the modified coaxial process, as it suffered more from the limitation of polymer chain entanglement threshold for maintaining structural uniformity of nanofibers. Using DMAc as sheath fluid in the modified process facilitated formation of thinner nanofibers without sacrificing their quality. The mechanism should be that an appropriate DMAc surrounding to the core polymer jet helps to retain it in a fluid state to experience a longer time electrical drawing, with little adverse influence on the polymer chain entanglements. Nanofiber diameters could also be tailored in a linear manner using the modified coaxial process simply through manipulating the sheath solvent flow rates. The modified coaxial process described here extends the capability of electrospinning process and opens a new way to obtain thinner nanofibers with fine structural uniformity. [ABSTRACT FROM AUTHOR]

Sustained-release ethyl cellulose (EC) micro-particles were prepared by electrospraying. Ketoprofen (KET) was taken as a model drug and various concentrations of EC functioned as a rate-controlling polymer. The morphology of the micro-particles was assessed using SEM. Images showed that as EC content increased, the granules shared similar surface characteristics containing pure EC. Micro-particle structures were analyzed by DSC, XRD, and FTIR. It was noted that the crystalline drug was converted into an amorphous form in all the granulations and that there was chemical interaction between KET and EC observed from FTIR. Dissolution studies revealed that as the amount of EC increased, the drug release rate decreased. This investigation suggests that electrospraying can be exploited as a useful tool for developing novel particulate drug delivery systems. [ABSTRACT FROM AUTHOR]

A modified co-axial electrospinning process including electrolyte solution as sheath fluid for preparing high quality polymer nanofibers is investigated. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing the modified process with sodium thiocyanate solutions in N, N-dimethylacetamide (DMAc) as sheath fluids. Field-emission scanning electron microscopy results demonstrated that the sheath sodium thiocyanate solutions had significant influence on the quality of PAN nanofibers. High quality PAN nanofibers in terms of fiber diameters and their distributions, surface morphology and structure have been successfully produced. The diameters of nanofibers ( D, nm) could be manipulated simply by adjusting the concentrations of sodium thiocyanate ( C, mg ml) in the sheath fluids with a scaling law of D = 324 C. The mechanism about the influence of sodium thiocyanate solutions on the formation of PAN fibers is discussed and it is felt that co-axial electrospinning with electrolyte solution is a facile process for achieving high quality polymer nanofibers. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The objective of the present investigation was to prepare novel solid dispersions (SDs) of poorly water-soluble drugs with special microstructural characteristics using electrospinning process. With the hydrophilic polymer polyvinylpyrrolidone as the filament-forming polymer and acetaminophen (APAP) as the poorly water-soluble drug model, SDs having a continuous web structure, and in the form of non-woven nanofiber membranes, were successfully prepared. The electrospun nanofiber-based SDs were compared with those prepared from three traditional SD processes such as freeze-drying, vacuum drying, and heating drying. The surface morphologies, the drug physical status, and the drug-polymer interactions were investigated by scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and attenuated total reflectance Fourier transform infrared. In vitro dissolution tests demonstrated that the electrospun nanofibers released 93.8% of the APAP content in the first 2 minutes and that the dissolution rates of APAP from the different SDs had the following order: electrospun membrane > vacuum-dried membrane ≈ freeze-dried membrane > heat-dried membrane. Electrospun nanofiber-based SDs showed markedly better dissolution-improving effects than the other SDs, mainly due to their huge surface area, high porosity resulting from web structure, and the more homogeneous distribution of APAP in the nanofiber matrix. [ABSTRACT FROM AUTHOR]

Rheological properties of microemulsions (MEs) and their printability in three dimensional printing (3DP) systems were investigated. A series of MEs with different contents of oil phase were prepared using sonication method with ibuprofen as model drug and soybean lecithin as emulfier. Stationary and transient rheological properties of MEs were investigated by ARES-SRF using concentric cylinders measuring systems. 3DP systems with piezoelectric drop-on-demand print heads were employed to test the printability of the MEs. Results demonstrate that the apparent viscosity and dynamic linear viscoelastic regions of the MEs are the most important parameters for continuous and stable printing of MEs by 3DP. The incorporation of drug in the MEs has little influence on the MEs’ stationary rheological behaviors and dynamic viscoelasticity, but the concentration of oil phase has a strong influence on them. The rheological property of binder liquids has a close relationship with their printability in 3DP system. [ABSTRACT FROM AUTHOR]