Improving the thermal and mechanical properties of phenolic fiber over boron modified high-ortho phenolic resin

Boron-modified high-ortho phenolic resins (BPRs) were prepared under normal pressure by using phenol and formaldehyde as raw materials, zinc acetate, and oxalic acid as catalysts, and boric acid as a modifier. Boron-modified phenolic fibers (BPFs) were prepared by melt spinning and curing in a mixture of formaldehyde and hydrochloric acid, followed by a heat treatment under high temperature. The structure, ortho–para ratio (O/P), molecular weight and distribution, spinnability, thermal stability, fiber strength, and morphology of the resins were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and fiber strength testing. The results showed that the addition of boric acid reduced the ortho reaction of the synthetic resin and the O/P value of phenolic resin. When the content of boric acid was 3 wt%, the thermal stability was the best, the O/P value was up to 3.26, and the weight average molecular weight (Mw) was 18745 g/mol. In Compared with the unmodified resin, the mass loss was increased by 33.7%, and finally the carbon yield was 51.2%. The tensile strength of the fibers reached 187.2 MPa and the elongation at break was 10.5%. By introducing boron into the molecular chain, the structure of the resin was improved, and the thermal stability and mechanical properties of the fibers were improved.

Preparation and heat-insulating properties of Al2O3-ZrO2(Y2O3) hollow fibers derived from cogon using an orthogonal experimental design

Bionic design is efficient to develop high-performance lightweight refractories with sophisticated structures such as hollow ceramic fibers. Here, we report a four-stage procedure for the preparation of Al2O3-ZrO2(Y2O3) hollow fibers using the template of cogon-a natural grass. Subsequently, to optimize the thermal performance of the fibers, four sets of preparation parameters, namely, x(Al2O3), solute mass ratio of the mixture, dry temperature, and sintering temperature were investigated. Through an orthogonal design, the optimal condition of each parameter was obtained as follows: x(Al2O3) was 0.70, solute mass ratio of the mixture was 15 wt%, dry temperature was 80 °C, and sintering temperature was 1100 °C. Overall, Al2O3-ZrO2(Y2O3) hollow fibers show relatively low thermal conductivity (0.1038 W m-1 K-1 at 1000 °C), high porosity (95.0%), and low density (0.05-0.10 g cm-3). The multiphase compositions and morphology of Al2O3-ZrO2(Y2O3) hollow fibers, which may contribute to their thermal properties, were also discussed.

Orthogonal experimental preparation of Sanguis Draconis- Polyvinylpyrrolidone microfibers by electrospinning

How to improve the bioavailability of the Sanguis Draconis (SD) is an important problem in the potential clinical applications. The aim of this study was to develop a drug delivery system to achieve high bioavailability of SD, a drug with poor water solubility. It will promote the research about new formulations of the SD and the other insoluble drugs. In this study, a highly biocompatible hydrophilic polymer, polyvinylpyrrolidone (PVP), was selected as a carrier, mixed with different proportions of SD to produce SD-PVP microfibers by solution electrospinning. By orthogonal experiments, the optimal spinning conditions of the preparation of SD-PVP fibers were investigated. The morphology of different proportions of SD-PVP microfibers was observed by scanning electron microscopy, and the phase characteristics were characterized by Fourier transform infrared spectrometry, X-ray diffraction, and differential scanning calorimetry. The hydrophilic properties of SD-PVP fiber membranes with different SD content were analyzed by the water contact angle assay. In vitro dissolution experiments were carried out to observe the dissolution of drugs in SD-PVP fiber membranes. The results showed that the diameter of SD-PVP fibers increased with the enlargement of SD content. A eutectic mixture was formed after blending PVP and SD, and the hydrogen bonds were formed between the SD and PVP with no chemical reaction occurred. The dispersion of SD in the fiber decreased with the increase of SD content. The higher the content of SD in the fiber, the more hydrophobic the fiber membrane. In vitro dissolution studies revealed that the dissolution content of SD from SD-PVP microfibers was significantly higher than that of the pure or original drug SD. However, as the SD content increased from 15% to 30%, the dissolution of the drug in the SD-PVP fibers decreased. The SD-PVP fiber prepared in this study showed much higher solubility than the original drug in vitro, which has great significance for the development of new dosage forms for the clinical application of SD, and it has a useful reference for the study of similar bioavailability of poorly soluble drugs.

Development of ciprofloxacin-loaded poly(vinyl alcohol) dry powder formulations for lung delivery

Polymeric microparticles are micro carriers for the sustained drug delivery of drugs in the lungs, used as alternatives to the use of established excipients. This study aims to develop and characterize inhalable ciprofloxacin (CPx)-loaded poly(vinyl alcohol) (PVA) microparticles by a single-step spray-drying procedure. The optimization of the processing parameters was achieved by an orthogonal design of the most relevant processing parameters (polymer concentration, feed rate and inlet temperature). The obtained spray-dried particles showed a drug encapsulation efficiency higher than 90%. Furthermore, PVA-CPx formulations, with drug contents up to 10 wt%, showed a morphology and size suitable for inhalation, with a sustained release profile over 24 h. Data from Fourier transformed infra-red spectroscopy and differential scanning calorimetry indicated absence of interaction between the polymer matrix and the drug. Aerodynamic assessment of PVA-CPx 10 wt% was determined by the next generation impactor (NGI), using spray-dried CPx as a control. The results showed improved values of mass median aerodynamic diameter (5.06±0.10μm) and a fine particle fraction (39.78±0.98%) when comparing with the CPx alone (5.33±0.39μm and 30.43±1.38%). This study highlights the potential of spray-dried PVA microparticles as drug carriers for lung local delivery of antibiotics.

Effect of scaffold morphology and cell co-culture on tenogenic differentiation of HADMSC on centrifugal melt electrospun poly (L‑lactic acid) fibrous meshes

Engineered tendon grafts offer a promising alternative for grafting during the reconstruction of complex tendon tears. The tissue-engineered tendon substitutes have the advantage of increased biosafety and the option to customize their biochemical and biophysical properties to promote tendon regeneration. In this study, we developed a novel centrifugal melt electrospinning (CME) technique, with the goal of optimizing the fabrication parameters to generate fibrous scaffolds for tendon tissue engineering. The effects of CME processing parameters, including rotational speed, voltage, and temperature, on fiber properties (i.e. orientation, mean diameter, and productivity) were systematically investigated. By using this solvent-free and environmentally friendly method, we fabricated both random and aligned poly (L-lactic acid) (PLLA) fibrous scaffolds with controllable mesh thickness. We also investigated and compared their morphology, surface hydrophilicity, and mechanical properties. We seeded human adipose derived mesenchymal stem cells (HADMSC) on various PLLA fibrous scaffolds and conditioned the constructs in tenogenic differentiation medium for up to 21 days, to investigate the effects of fiber alignment and scaffold thickness on cell behavior. Aligned fibrous scaffolds induced cell elongation and orientation through a contact guidance phenomenon and promoted HADMSC proliferation and differentiation towards tenocytes. At the early stage, thinner scaffolds were beneficial for HADMSC proliferation, but the scaffold thickness had no significant effects on cell proliferation for longer-term cell culture. We further co-seeded HADMSC and human umbilical vein endothelial cells (HUVEC) on aligned PLLA fibrous mats and determined how the vascularization affected HADMSC tenogenesis. We found that co-cultured HADMSC-HUVEC expressed more tendon-related markers on the aligned fibrous scaffold. The co-culture systems promoted in vitro HADMSC differentiation towards tenocytes. These aligned fibrous scaffolds fabricated by CME technique could potentially be utilized to repair and regenerate tendon defects and injuries with cell co-culture and controlled vascularization.