Electrospinning of PLA and PLA/POSS nanofibers: Use of Taguchi optimization for process parameters

It is known that electrospinning is the most practical technique to obtain unique nanofibrous structures, such as neat PLA (polylactide) and PLA filled with POSS (Polyhedral Oligomeric Silsesquioxane) particles. On the other hand, due to the so many different process parameters to consider, production of these fibers are extremely difficult and time consuming. That is, use of a certain statistical optimization technique in the design of experiments would be necessary. Therefore, the main purpose of this study was to determine the optimum electrospinning parameters by applying the Taguchi technique first to neat PLA and then to reveal the applicability of these parameters for the electrospinning of PLA/POSS nanofibers. It was observed that instead of conducting 81 experiments to determine the most significant four optimum process parameters for PLA, use of Taguchi L₉ orthogonal array experiment matrix, that is, conducting only nine experiments, reduced time, labor and material consumption considerably. For the smallest electrospun PLA fiber diameter, the optimum parameters determined were; “PLA solution concentration” of 8% w/v, “solution feeding rate” of 1.8 mL/h, “needle-to-collector distance” of 18 cm, and “applied voltage” of 15 kV. Moreover, it was generally concluded that these same parameters could be also used for the electrospinning of PLA/POSS nanofibers after addition of only 3 wt% KCl salt into the polymer solution.     

Oxidation of sulfur components in diesel fuel using Fe-TAML catalysts and hydrogen peroxide

Dibenzothiophene-derivatives are catalytically oxidized to their corresponding sulfone product in homogeneous and two-liquid phase systems by H₂O₂ with an iron containing tetraamidomacrocyclic ligand (TAML) catalyst, Fe-TAML^®. The reaction medium is slightly caustic, pH 8, and uses t-BuOH as a co-solvent for solubilizing the dibenzothiophene starting compounds and their oxidation products. Fe-TAML^® catalyst concentrations are in the low micromolar range. H₂O₂ consumption is nearly stoichiometric (two-equivalents) in homogeneous conditions and only slightly less efficient under two-liquid phase conditions. The catalytic process when applied to a sample of commercial diesel fuel occurs under mild conditions with respect to temperature (50 °C), pressure (1 atm), and time (3 h), to remove greater than 75% of the total sulfur content of the fuel after secondary treatment with silica. Both alkyl-benzothiophenes and alkyl-dibenzothiophenes compounds in the diesel fuel were oxidized by the Fe-TAML^®/H₂O₂ system which facilitated their adsorption onto the silica. The mild reaction conditions result in no detectable over-oxidation of alkyl-dibenzothiophenes.     

Polycaprolactone‐hydroxy apatite composites for tissue engineering applications

In this study, scaffolds with polycaprolactone (PCL) and hydroxy apatite (HA) were produced. Their properties are not sufficient to be used alone. Oleic Acid (OA) and glycerol monooleate (GMO) as organic additives were selected for a homogeneous distribution of the ceramic material in the polymer matrix. Biocomposite materials were prepared with solvent casting‐salt leaching technique using dichloromethane as the solvent. Salt was used as the porosifier. Materials were kept in simulated body fluid (SBF) to determine the bioactivity in vitro conditions. FTIR and EDX analyses for chemical characterization, tensile and compressive tests for mechanical properties, SEM analyses for surface properties and BET analyses for pore sizes, total surface areas and total pore volumes of scaffolds were performed. FTIR, EDX, and SEM analyses were repeated after SBF treatment. Pore diameters were highly increased with 3 and 20 wt% HA addition. Small amount of GMO addition is more effective on pore size. Mechanical properties of scaffolds were suitable for soft tissue applications, as smooth muscle cells, skin and cancellous bone. The cytotoxicity and cell proliferation on scaffolds were studied with smooth muscle cells (SMC) and L929 fibroblastic cells in vitro. No cytotoxic effect was observed for the scaffolds in both cell types. J. VINYL ADDIT. TECHNOL., 24:248–261, 2018. © 2016 Society of Plastics Engineers     

Evaluation of normal-appearing white matter with perfusion and diffusion MRI in patients with treated glioblastoma

Magnetic Resonance Materials in Physics, Biology and Medicine - We tried to reveal how the normal appearing white matter (NAWM) was affected in patients with glioblastoma treated with...     

Main-chain polybenzoxazine nanofibers via electrospinning

Here we report the successful production of nanofibers from main-chain polybenzoxazines (MCPBz) via electrospinning without using any other carrier polymer matrix. Two different types of MCPBz (PBA-ad6 and PBA-ad12) were synthesized by using two types of difunctional amine (1,6-diaminohexane and 1,12-diaminododecane), bisphenol-A, and paraformaldehyde as starting materials through a Mannich reaction. ¹H NMR and FTIR spectroscopy studies have confirmed the chemical structures of the two MCPBz. We were able to obtain highly concentrated homogeneous solutions of the two MCPBz in chloroform/N,N-dimethylformamide (DMF) (4:1, v/v) solvent system. The electrospinning conditions were optimized in order to produce bead-free, uniform and continuous nanofibers from these two MCPBz by varying the concentrations of PBA-ad6 (30–45%, w/v) and PBA-ad12 (15–20%, w/v) in chloroform/DMF (4:1, v/v). The bead-free fiber morphology was evidenced under SEM imaging when PBA-ad6 and PBA-ad12 were electrospun at solution concentration of 40% and 18% (w/v), respectively. The nanofibrous mats of MCPBz were obtained as free-standing material, yet, PBA-ad12 mat was more flexible than and PBA-ad6 mat. Furthermore, the curing studies of these MCPBz nanofibrous mats were performed to obtain cross-linked materials.     

Conducting polymers of terepthalic acid bis-(2-thiophen-3-yl-ethyl) ester and their electrochromic properties

Terepthalic acid bis-(2-thiophen-3-yl-ethyl)ester (TATE) was synthesized through the reaction of 2-thiophen-3-yl-ethanol and terepthaloyl chloride. Homopolymer of TATE was synthesized via potentiostatic and potentiodynamic methods by using tetrabutylammonium tetrafluoroborate (TBAFB) as the supporting electrolyte in dichloromethane/borontrifluoride ethylether solvent mixture (DM/BFEE) (8:2, v/v). Copolymerisation of TATE with thiophene was achieved in DM/BFEE solvent mixture (8:2, v/v) by using TBAFB as the supporting electrolyte in the presence of thiophene. The chemical structure of monomer is characterised via NMR and FTIR. Both homopolymer (PTATE) and copolymer P(TATE-co-Th) were characterised by various techniques including cyclic voltammetry, FTIR, scanning electron microscopy and UV-VIS spectroscopy. Conductivities of samples were measured by four probe technique. Optoelectrochemical analysis indicates that the homopolymer and copolymer have an electronic band gap, measured as the onset of the π-to-π* transition, as 2.17 and 2.00 eV, respectively.     

Design and development of a self-microemulsifying drug delivery system of olmesartan medoxomil for enhanced bioavailability

Olmesartan medoxomil (OM) is a hydrophobic antihypertensive drug with low bioavailability (26%) and is known to have adverse effects such as celiac disease and enteropathy. The purpose of this study was to develop SMEDDS to increase bioavailability and decrease potential side effects of OM. Hydrophilic lipophilic balance was calculated by testing solubility of OM in different oils, surfactants, and cosurfactants to obtain the most suitable combination of SMEDDS. Pseudoternary phase diagram was used to select the better oil/water formulation of SMEDDS. After a test for 3-month stability, dissolution tests and parallel artificial membrane permeability assay (PAMPA) were conducted to investigate drug solubility and permeability. Biodistribution of fluorescent marked SMEDDS was observed by using in vivo imaging system. The pharmacodynamics of the drug were determined by measuring blood pressure from tails of rats. At the end of the experiment, intestines were examined for adverse effects of OM. Compared with tablet formulation according to the dissolution study, SMEDDS formulation showed 1.67 times improvement in solubility of OM. PAMPA studies suggested a much faster permeability rate for OM SMEDDS compared to the suspension form. Labeled SMEDDS gave 3.96 times stronger fluorescent emission than control dye administered mice in in vivo imaging system (IVIS^®) studies, indicating an increased bioavailability. Treating effect of SMEDDS was 3.1 times more efficient compared to suspension in hypertensive rats. It caused neither celiac-like enteropathy nor diarrhea, during 21-day noninvasive blood pressure system (NIBP) assay. Our results suggest that SMEEDS formulation improves dissolution and oral bioavailability of OM while reducing its adverse effects.     

The Effects of Mg Substitution in Bi-2223 Superconductors

The effects of Mg substitution in Bi-2223 superconductor system has been studied for the Bi_1.7Pb_0.3Sr₂Ca₂Cu_3−x Mg _x O _y nominal composition (x=0.00, 0.05, 0.10, 0.15 and 0.20) which was prepared by the conventional solid-state reaction. The properties of these compounds have been investigated by measuring the electrical resistivity, X-ray diffraction (XRD) and density. Also, scanning electron microscopy (SEM) was employed to investigate the surface microstructure of the samples. It has been found that the effects of Mg substitution support the development of both the Bi-2212 and Bi-2223 phases. These measurements and analyses enable us to discuss the effects of Mg dopant on superconducting properties. We found that onset critical temperatures (T _c, onset) decrease with addition x>0.10 in resistivity measurements. The presence of Mg influenced the microstructure of the samples and decreased the mean grain size of Bi-2223 grains up to x=0.10.     

Nanoliter Scale Parallel Liquid–Liquid Extraction for High-Throughput Purification on a Droplet Microarray

In the current drug discovery process, the synthesis of compound libraries is separated from biological screenings both conceptually and technologically. One of the reasons is that parallel on-chip high-throughput purification of synthesized compounds is still a major challenge. Here, on-chip miniaturized high-throughput liquid–liquid extraction in volumes down to 150 nL with efficiency comparable to or better than large-scale extraction utilizing separation funnels is demonstrated. The method is based on automated and programmable merging of arrays of aqueous nanoliter droplets with organic droplets. Multi-step extraction performed simultaneously or with changing conditions as well as handling of femtomoles of compounds are demonstrated. In addition, the extraction efficiency is analyzed with a fast optical readout as well as matrix-assisted laser desorption ionization-mass spectrometry on-chip detection. The new massively parallel and miniaturized purification method adds another important tool to the chemBIOS concept combining chemical combinatorial synthesis with biological screenings on the same miniaturized droplet microarray platform, which will be essential to accelerate drug discovery.     

Synthesis and characterization of bio-based benzoxazines derived from thymol

In the present study, bio-based benzoxazine resins were synthesized from bio-based phenolic compound; thymol, and three different amines; ethylamine, aniline and 1,6-diaminohexane, and paraformaldehyde by solvent-free condensation reaction. The chemical structures of bio-based benzoxazines; T-ea (thymol, ethylamine), T-a (thymol, aniline), and T-dh (thymol, 1,6-diaminohexane) were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared (FTIR) spectroscopy, elemental analysis, and high-resolution mass spectrometry. The curing studies of T-ea, T-a, and T-dh bio-based benzoxazines were performed by stepwise thermal treatment at 150, 175, 200, 225, and 250 °C. The polymerization (ring-opening and crosslinking reactions) of T-ea, T-a, and T-dh bio-based benzoxazines was investigated by FTIR spectroscopy. Cure analysis was conducted using differential scanning calorimetry and the changes in thermal properties of the T-ea, T-a, and T-dh bio-based benzoxazine resins and their corresponding thermally crosslinked polybenzoxazines PT-ea, PT-a, and PT-dh were studied by thermogravimetric analyzer. The results indicated that all the thymol-based polybenzoxazines have shown enhanced thermal stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47371.