Degradation and Mechanical Behavior of Fish Gelatin/Polycaprolactone AC Electrospun Nanofibrous Meshes

With the increasing interest in biopolymer nanofibers for diverse applications, the characterization of these materials in the physiological environment has become of equal interest and importance. This study performs first-time simulated body fluid (SBF) degradation and tensile mechanical analyses of blended fish gelatin (FGEL) and polycaprolactone (PCL) nanofibrous meshes prepared by a high-throughput free-surface alternating field electrospinning. The thermally crosslinked FGEL/PCL nanofibrous materials with 84–96% porosity and up to 60 wt% PCL fraction demonstrate mass retention up to 88.4% after 14 days in SBF. The trends in the PCL crystallinity and FGEL secondary structure modification during the SBF degradation are analyzed by Fourier transform infrared spectroscopy. Tensile tests of such porous, 0.1–2.2 mm thick FGEL/PCL nanofibrous meshes in SBF reveal the ultimate tensile strength, Young's modulus, and elongation at break within the ranges of 60–105 kPa, 0.3–1.6 MPa, and 20–70%, respectively, depending on the FGEL/PCL mass ratio. The results demonstrate that FGEL/PCL nanofibrous materials prepared from poorly miscible FGEL and PCL can be suitable for selected biomedical applications such as scaffolds for skin, cranial cruciate ligament, articular cartilage, or vascular tissue repair.     

Interlaboratory study on lipid oxidation during accelerated storage trials with rapeseed and sunflower oil analyzed by conjugated dienes as primary oxidation products

Accelerated storage tests are frequently used to assess the oxidative stability of foods and related systems due to its reproducibility. Various methods and experimental conditions are used to measure lipid oxidation. Differences between laboratories make it necessary to determine the repeatability and reproducibility of oxidation tests performed under the same conditions. The objective of the present interlaboratory study was to evaluate the outcome of a storage test for two different bulk oils, sunflower oil (SFO) and rapeseed oil (RSO), during a period of 9 weeks at 20°C, 30°C, 40°C, and 60°C. Sixteen laboratories were provided with bottled oils and conducted the storage tests according to a detailed protocol. Lipid oxidation was monitored by the formation of conjugated dienes (CD) and the activation energy (E_a) was determined for comparative purposes and statistically evaluated. An increase in CD formation was observed for both oils when the storage temperature was increased in all laboratories. The E_a,1 ranged from 47.9 to 73.3 kJ mol⁻¹ in RSO and from 27.8 to 62.6 kJ mol⁻¹ in SFO, with average values of 58.2 and 46.8 kJ mol⁻¹, respectively. The reproducibility coefficients were 10.9% and 18.2% for RSO and SFO, respectively. Practical applications: In order to compare results on oxidative stability of foods derived from different studies, the reproducibility of storage tests and methods employed to evaluate the oxidation level should be considered. This study provides fundamental data on the reproducibility of lipid oxidation under accelerated storage conditions and defines important parameters to be considered for the conduction of experiments.     

Imaging of KCa3.1 Channels in Tumor Cells with PET and Small-Molecule Fluorescent Probes

The Ca²⁺ activated K⁺ channel K_Ca3.1 is overexpressed in several human tumor cell lines, e. g. clear cell renal carcinoma, prostate cancer, non-small cell lung cancer. Highly aggressive cancer cells use this ion channel for key processes of the metastatic cascade such as migration, extravasation and invasion. Therefore, small molecules, which are able to image this K_Ca3.1 channel in vitro and in vivo represent valuable diagnostic and prognostic tool compounds. The [¹⁸F]fluoroethyltriazolyl substituted senicapoc was used as positron emission tomography (PET) tracer and showed promising properties for imaging of K_Ca3.1 channels in lung adenocarcinoma cells in mice. The novel senicapoc BODIPY conjugates with two F-atoms ( 9 a ) and with a F-atom and a methoxy moiety ( 9 b ) at the B-atom led to the characteristic punctate staining pattern resulting from labeling of single K_Ca3.1 channels in A549-3R cells. This punctate pattern was completely removed by preincubation with an excess of senicapoc confirming the high specificity of K_Ca3.1 labeling. Due to the methoxy moiety at the B-atom and the additional oxyethylene unit in the spacer, 9 b exhibits higher polarity, which improves solubility and handling without reduction of fluorescence quantum yield. Docking studies using a cryo-electron microscopy (EM) structure of the K_Ca3.1 channel confirmed the interaction of 9 a and 9 b with a binding pocket in the channel pore.     

The effectuation of seawater on the microstructural features and the compressive strength of fly ash blended cement at early and later ages

The current work scrutinizes the effectuation of seawater on morphological properties, pore structure, and compressive strength during the hydration process of fly ash blended cement at 3, 7, 28, 56, and 90 days to better understand the influence of salinity conditions of seawater on the microstructural modification and strength development of the hydration products as well as the total porosity. The chemical reaction's mechanism of mightily soluble salts, for example, Mg₂SO₄ and NaCl, with hydrated fly ash and blended cement (calcium-bearing phases) was also confirmed. Fourier-transform infrared spectroscopy has been appointed to observe and characterize the energetics of variation in the formulation of portlandite (CH), calcium silicate hydrate, gypsum (Gy), ettringite (AFt), and calcium chloroaluminate (Friedel's salt [FS]) throughout the hydration process of fly ash blended cement with seawater in comparison with deionized water. X-ray diffraction analysis exposed that the peak intensities of FS, portlandite, and some particular phases of the hydrated fly ash blended cement in seawater are higher and sharper than the comparable peaks in deionized water. Mercury intrusion porosimetry-measurements have been appointed that the total porosity of artificial seawater (ASW) was decreased from 28.9% at 3 days to 19.4% at 56 days. In addition, the average, median, and critical pore diameter were decreased in ASW while compared to deionized water (DIW). The reaction products of this work were also characterized using scanning electron microscopy, EDS, compressive strength, and isothermal calorimeter.     

Photo‐induced protonation and conductivity of polyaniline/poly(ethylene glycol) and polyaniline/[poly(ethylene glycol)‐grafted polyaniline] composites

Composites of polyaniline in its emeraldine base form (PANI‐EB) and photo‐acid generators (PAG) show an increase in conductivity upon photo‐irradiation due to the protonation of PANI‐EB. Such materials may be utilized to fabricate conducting patterns by photo‐irradiation. However, the conductivity obtained by direct irradiation of PANI‐EB/PAG composites was normally quite low (<10^?3 S/cm) due to aggregation of highly loaded PAG. In this work, poly(ethylene glycol) (PEG), which is a proton transfer polymer, was added to PANI‐EB/PAG. Results showed that addition of low M_w (550) PEG significantly enhance the photo‐induced conductivity. Conductivities as high as 10^?1–10⁰ S/cm were observed after photo‐irradiation. This conductivity is comparable to that of PANI‐salt synthesized by oxidizing aniline in the presence of an acid. High M_w (8000) PEG is much less effective than PEG 550, which is attributed to its lower compatibility with PANI. PEG‐grafted PANI (N‐PEG‐PANI) was also studied as an additive. Composites of PANI‐EB and N‐PEG‐PANI showed conductivity as high as 10² S/cm after treatment with HCl vapor. The photo‐induced conductivity of the N‐PEG‐PANI/PANI‐EB/PAG composite reached 10^?2–10^?1 S/cm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Evaluation of the influence of polyoxide‐based surfactants on the separation process of model emulsions of asphaltenes using the FTIR‐ATR technique

During extraction of crude oil, water is generally present in the oil. This water‐in‐oil (w/o) mixture undergoes turbulent flow that promotes sheer forces, resulting in the appearance of emulsions. These emulsions can be highly stable due to the presence of compounds with polar characteristics such as asphaltenes, which act as natural emulsifiers and form resistant films at the oil–water interface. Nonionic surfactants based on polyoxides are widely used to prevent the formation or to break down w/o emulsions. To shed more light on the destabilization mechanism of w/o emulsions promoted by these surfactants, in this study the techniques of tensiometry and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR‐ATR) were applied to study the interface formed by poly(ethylene oxide)‐poly(propylene oxide) (PEO‐PPO) block copolymers and asphaltenic petroleum fractions. Initially, the critical micelle concentration of the copolymers in aqueous solution was determined. The results agreed with those found by tensiometry. The bottle test was used to evaluate the break‐down of the w/o emulsions in the presence of the PEO‐PPO block copolymers, and the results presented good agreement with those obtained by tensiometry and FTIR‐ATR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Wetting Behavior of Ibuprofen Racemate Surfaces

The wetting behavior and detailed surface energetics of a racemate crystalline system were measured via contact angle measurements and inverse gas chromatography at finite concentrations. The advancing contact angles for water, diiodomethane, formamide, and ethylene glycol were measured on specific facets for racemic ibuprofen and S-(+)-ibuprofen single macroscopic crystals, and were found to be facet dependent for both systems. This observation demonstrates that variation in molecular orientation within the crystal lattice results in variations in exposed surface chemistry for differing facets, which results in anisotropic wetting behavior as previously reported. Surface free energy profiles of the ibuprofen racemates determined using a novel inverse gas chromatography method showed that powder samples (75–150 µm particle diameter) exhibited relatively homogeneous surface energies, with similar values of γ_SV ^d to those obtained by the contact angle analysis. These results lead us to conclude that ibuprofen exhibited a low level of surface heterogeneity, with the dominant facet of these powders exhibiting a low γ_SV ^d, with high energetic sites estimated to be < 3% of exposed available surface.     

Challenges in nucleic acid‐lipid films for transfection

The use of surface‐based methods for the delivery of therapeutics has recently generated increasing interest. These platforms have tremendous potential to minimize detrimental side effects associated with systemic delivery by localizing the therapeutic vehicle, and thus provide higher local doses for improved efficacy. Cationic lipids are one of the most commonly used synthetic carriers for the delivery of genetic cargo, such as DNA and RNA. However, reports on the use of lipid‐based films for gene delivery are scarce. Here we investigate the use of a lipid‐based film for the in vitro delivery of plasmid DNA. Solid DNA‐lipid films show very low levels of transfection, while identical complexes prepared for bolus delivery provide high levels of transfection when used directly. We investigate the mechanism, whereby the activity of these solid‐state films is lost and suggest methods for circumventing these challenges and restoring the efficacy of these films as gene delivery platforms. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3203–3213, 2013     

Melt processing and characterization of polyvinyl alcohol and polyhydroxyalkanoate multilayer films

Multilayer films for food packaging applications composed of polyvinyl alcohol (PVOH) as the core layer and polyhydroxyalkanoate (PHA) as the outer skin layers were produced by the co‐extrusion process. Rheological properties of PVOH and PHA were performed and analyzed before co‐extruding into a cast film. Analysis of the rheological data indicated the processing temperatures and grades of the PVOH and PHA polymers that would produce similar viscosity and melt flow properties. To improve adhesion of the layers, PHA was grafted with maleic anhydride using a dicumyl peroxide initiator to provide a tie layer material, which improved the peel strength of the PHA and PVOH layers by over 2×. Oxygen transmission rate (OTR) testing showed that the multilayer sample provided an OTR of 27 cc/m²‐day at 0% relative humidity (RH) and rates of 41 and 52 cc/m²‐day at relative humidity values of 60% and 90% RH, respectively. This indicates significant barrier performance enhancement over monolayer PVOH that provided an OTR of 60 cc/m²‐day at 0% RH and 999 cc/m²‐day at 60% RH. Biodegradation testing of the films in the marine environment showed that both the unmodified and maleated PHA polymers displayed high levels of mineralization, whereas the PVOH material did not. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013