Characterisation of internal morphologies in electrospun fibers by X-ray tomographic microscopy

Unveiling the Inner Structure of Micrometric Hollow Polymeric Fibers Using Synchrotron X-Ray Nanotomography

In this study, a novel application of synchrotron X-ray nanotomography based on high-resolution full-field transmission X-ray microscopy for characterizing the structure and morphology of micrometric hollow polymeric fibers is presented. By employing postimage analysis using an open-source software such as Tomviz and ImageJ, various key parameters in fiber morphology, including diameter, wall thickness, wall thickness distribution, pore size, porosity, and surface roughness, were assessed. Electrospun polycaprolactone fibers with micrometric diameters and submicrometric features with induced porosity via gas dissolution foaming were used to this aim. The acquired synchrotron X-ray nanotomography data were analyzed using two approaches: 3D tomographic reconstruction and 2D radiographic projection-based analysis. The results of the combination of both approaches demonstrate unique capabilities of this technique, not achievable by other available techniques, allowing for a full characterization of the internal and external morphology and structure of the fibers as well as to obtain valuable qualitative insights into the overall fiber structure.

Determination of aflatoxin B1 by novel nanofiber-packed solid-phase extraction coupled with a high performance liquid chromatography-fluorescence detector

A novel analytical proposal based on nanofiber-packed solid-phase extraction coupled with high performance liquid chromatography-fluorescence detector (HPLC-FLD) has been successfully developed for determining aflatoxin B1 (AFB1) in foods. Four types of nanofibers, including polystyrene (PS) nanofibers, polypyrrole (PPY) nanofibers, polystyrene-acrylic resin (PS-AR) nanofibers, and polystyrene-polyvinyl pyrrolidone (PS-PVP) nanofibers, were fabricated by electrospinning and utilized to prepare a home-made extraction device. In this study, the factors of different fibers, namely, fiber dosage, pH of extraction solution, type of salt ion, concentration of salt ion, and volume of the eluent were optimized. Under optimized conditions, the method showed good linearity in the range of 0.1-40 ng mL^-1 with a correlation coefficient greater than 0.999 and good inter-day accuracy (90.8-112.7% recovery) and precision (1.8-3.6% intra-day RSDs, 2.6% inter-day RSD), and the limit of detection (LOD) was 0.05 ng mL^-1. Due to its cost-effective, time-saving, environmentally friendly, and simple performance, it has the potential to be utilized to determine aflatoxins in complicated matrices.

Electrospun Nanofibers of Natural and Synthetic Polymers as Artificial Extracellular Matrix for Tissue Engineering

Many types of polymer nanofibers have been introduced as artificial extracellular matrices. Their controllable properties, such as wettability, surface charge, transparency, elasticity, porosity and surface to volume proportion, have attracted much attention. Moreover, functionalizing polymers with other bioactive components could enable the engineering of microenvironments to host cells for regenerative medical applications. In the current brief review, we focus on the most recently cited electrospun nanofibrous polymeric scaffolds and divide them into five main categories: natural polymer-natural polymer composite, natural polymer-synthetic polymer composite, synthetic polymer-synthetic polymer composite, crosslinked polymers and reinforced polymers with inorganic materials. Then, we focus on their physiochemical, biological and mechanical features and discussed the capability and efficiency of the nanofibrous scaffolds to function as the extracellular matrix to support cellular function.

Phenolic-amine chemistry mediated synergistic modification with polyphenols and thrombin inhibitor for combating the thrombosis and inflammation of cardiovascular stents

Antithrombogenicity, anti-inflammation, and rapid re-endothelialization are central requirements for the long-term success of cardiovascular stents. In this work, a plant-inspired phenolic-amine chemistry strategy was developed to combine the biological functions of a plant polyphenol, tannic acid (TA), and the thrombin inhibitor bivalirudin (BVLD) for tailoring the desired multiple surface functionalities of cardiovascular stents. To realize the synergistic modification of TA and BVLD on a stent surface, an amine-bearing coating of plasma polymerized allylamine was firstly prepared on the stent surface, followed by the sequential conjugation of TA and BVLD in alkaline solution based on phenolic-amine chemistry (i.e., Michael addition reaction). TA and BVLD were successfully immobilized onto the stent surface with considerable amounts of 330 ± 12 and 930 ± 80 ng/cm², respectively. The abundant phenolic hydroxyl groups of TA imparted the stent with ability to suppress inflammation. Meanwhile, BVLD provided an antithrombogenic and endothelial-friendly microenvironment. As a result, the combined functions of the TA and BVLD facilitate the rapid stent re-endothelialization for reduced intimal hyperplasia in vivo, and may be a promising strategy to address the clinical complications associated with restenosis and late stent thrombosis.

Co-Immobilization of Ce6 Sono/Photosensitizer and Protonated Graphitic Carbon Nitride on PCL/Gelation Fibrous Scaffolds for Combined Sono-Photodynamic Cancer Therapy

Aiming at developing a moderate and efficient sono-photodynamic therapy for breast cancer, tissue engineering scaffolds may provide an easy and efficient strategy to eliminate serious side effects in conventional surgery or chemotherapy, and thus, they are highly desired. However, the development of ideal sono-photodynamic therapeutic scaffolds is always hindered by the poor stability and incompatibility between the different biomaterial components. Herein, the Food and Drug Administration (FDA)-approved sono/photosensitizer Chlorin e6 (Ce6) was successfully and tightly incorporated into electrospun polycaprolactone/gelatin (PG) scaffolds via positively charged protonated g-C₃N₄ nanosheets (pCN). The PG fibers were precoated with graphene oxide (GO) to enable the assembly of pCN on the surface through electrostatic interactions. The Ce6@pCN-GO-PG composite scaffolds exhibited good cytocompatibility and excellent sono-photodynamic activity, leading to distinctly boosted reactive oxygen species (ROS) generation and a 95.8% inactivation rate of breast cancer cells through a synergistic sono-photodynamic process triggered by an 808 nm laser and 1 MHz ultrasound (US) excitation, within the clinical therapeutic dose. The as-developed scaffolds with unique ultrasound cavitation therapeutic effects can be used not only for complete eradication of tumor cells after surgery but also as a cell behavior observation platform of sono-photodynamic cancer therapy.

Comparison of Adsorption/Desorption of Volatile Organic Compounds (VOCs) on Electrospun Nanofibers with Tenax TA for Potential Application in Sampling

The objective of this study was to compare the adsorption/desorption of target compounds on homemade electrospun nanofibers, polystyrene (PS) nanofibers, acrylic resin (AR) nanofibers and PS-AR composite nanofibers with Tenax TA. Ten volatile organic compounds (VOCs) were analyzed by preconcentration onto different sorbents followed by desorption (thermal and solvent orderly) and analysis by capillary gas chromatography. In comparison to Tenax TA, the electrospun nanofibers displayed a significant advantage in desorption efficiency and adsorption selectivity. Stability studies were conducted as a comparative experiment between PS-AR nanofibers and Tenax TA using toluene as the model compound. No stability problems were observed upon storage of toluene on both PS-AR nanofibers and Tenax TA over 60 hours period when maintained in an ultra-freezer (-80°C). The nanofibers provided slightly better stability for the adsorbed analytes than Tenax TA under other storage conditions. In addition, the nanofibers also provided slightly better precision than Tenax TA. The quantitative adsorption of PS-AR nanofibers exhibited a good linearity, as evidenced by the 0.988-0.999 range of regression coefficients (R). These results suggest that for VOCs sampling the electrospun nanofibers can be a potential ideal adsorbent.

Adsorption/desorption performance of volatile organic compounds on electrospun nanofibers

Electrospun nanofibers possess the advantages of the certain selectivity, favorable adsorption/desorption efficiency, short adsorption equilibration time and preferable regeneration and can be a potential adsorbent for VOCs.

Electrospun nanofibers-mediated on-demand drug release

A living system has a complex and accurate regulation system with intelligent sensor-processor-effector components to enable the release of vital bioactive substances on demand at a specific site and time. Stimuli-responsive polymers mimic biological systems in a crude way where an external stimulus results in a change in conformation, solubility, or alternation of the hydrophilic/hydrophobic balance, and consequently release of a bioactive substance. Electrospinning is a straightforward and robust method to produce nanofibers with the potential to incorporate drugs in a simple, rapid, and reproducible process. This feature article emphasizes an emerging area using an electrospinning technique to generate biomimetic nanofibers as drug delivery devices that are responsive to different stimuli, such as temperature, pH, light, and electric/magnetic field for controlled release of therapeutic substances. Although at its infancy, the mimicry of these stimuli-responsive nanofibers to the function of the living systems includes both the fibrous structural feature and bio-regulation function as an on demand drug release depot. The electrospun nanofibers with extracellular matrix morphology intrinsically guide cellular drug uptake, which will be highly desired to translate the promise of drug delivery for the clinical success.

Selective isolation of the electron or hole in photocatalysis: ZnO-TiO2 and TiO2-ZnO core-shell structured heterojunction nanofibers via electrospinning and atomic layer deposition

Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO2 in two combinations where only the 'shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO2 CSHJ, e/h pairs are created mainly in TiO2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the 'shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO2-ZnO CSHJ. The results further revealed that the TiO2-ZnO CSHJ shows ∼1.6 times faster PCA when compared to the ZnO-TiO2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes.

Water-soluble non-polymeric electrospun cyclodextrin nanofiber template for the synthesis of metal oxide tubes by atomic layer deposition

We report on the suitability of water-soluble non-polymeric electrospun cyclodextrin (CD) nanofiber templates by using atomic layer deposition (ALD) to yield metal oxide tubes.

Systhesis, phase transformation and photoluminescence properties of Eu:La(1-x)Gd(x)VO4 nanofibers by electrospinning method

One dimensional Eu:La(1-x)Gd(x)VO(4) nanofibers were successfully prepared via an electrospinning method. Thermogravimetry and differential scanning calorimeter (TG-DSC), X-ray diffraction, Raman spectroscopy, scanning electron microscopy and photoluminescence were used to characterize the samples. The nanofibers crystallized well below 600 °C and with the increase of Gd contents, the nanofibers crystallized in a zircon-type structure. The Raman spectra shifted to higher frequency with the increase of Gd content for zircon Eu:La(1-x)Gd(x)VO(4). The peaks of photoluminescence spectra shift towards longer wavelength when Gd replaces La and when x = 0.4, the photoluminescence intensity reaches its maximum value. The band structure and density of states of m-LaVO(4), t-LaVO(4), t-LaGdVO(4) and t-GdVO(4) were calculated by local-spin density approximation (LSDA) band theory with Hubbard term of U. The band gap of t-LaGdVO(4) is just the average of t-LaVO(4) and t-GdVO(4). In t-LaGdVO(4), La 5p states are highly localized.

Enhanced visible-light-driven photocatalysis of surface nitrided electrospun TiO2 nanofibers

Enhanced visible-light-driven photocatalysis of TiO(2) nanofibers have been prepared by the electrospinning method combined with a surface nitridation process. The visible-light-driven photo-catalytic activity of surface nitrided TiO(2) (N-TiO(2)) nanofibers has been evaluated using rhodamine B indicator, and it was found that the visible-light-driven photocatalytic activity of the electrospun TiO(2) nanofibers could be enhanced by nitridation in NH(3) atmosphere. The optimal visible-light photocatalytic activity of N-TiO(2) nanofibers exceeded that of pure TiO(2) nanofibers by a factor of more than 12. The nitridation temperature under NH(3) flow was found to play an important part in the performance of N-TiO(2) nanofibers, and the optimum temperature is 500 °C. Structure, morphology and photoluminescence of these nanofibers were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM) and photoluminescence (PL) spectroscopy. The mechanism of the enhancement of visible-light-driven photocatalytic activity by surface nitridation has been discussed.