Poly(vinyl alcohol)-α-chitin composites reinforced by oil palm empty fruit bunch fiber-derived nanocellulose

Poly(vinyl alcohol)-α-chitin composite films reinforced by oil palm empty fruit bunch fiber-derived nanocellulose were prepared by casting technique. Fourier transform infrared spectroscopy analysis revealed partial miscibility between chitin and poly(vinyl alcohol) through hydrogen bonding, as supported by differential scanning calorimetry and field emission scanning electron microscopy. Tensile strength of the poly(vinyl alcohol)/chitin films increased with α-chitin content varied from 10 to 30?wt%, which was from 29.06 to 39.27?MPa. With the addition of 1?wt% nanocellulose, a maximum improvement of 57.64 and 50.66% in terms of tensile strength and Young’s modulus was achieved, respectively.     

Understanding Behavior of Polycaprolactone–Gelatin Blends under High Pressure CO<Subscript>2</Subscript>

Polycaprolactone (PCL) is widely used in biomedical applications as electrospun fibers or porous foams. As PCL is synthetic polymer, many researchers have explored blends of PCL–gelatin to combine mechanical and bioactive properties of individual components. High pressure carbon dioxide (CO2) has been studied to foam and impregnate many biocompatible polymers. In case of PCL–gelatin blends, certain compositions can be swelled reversibly under high pressure CO₂ without permanent deformation. This allows successful impregnation of PCL–gelatin blends under CO₂. This study summarizes effect of different treatments adopted during impregnation process including high pressure CO2 on several blend compositions of PCL–gelatin blends. Stress relaxation, polymer melting and dissolution were observed during several treatments which affects porosity and scaffold structure significantly. Results summarized in this study will aid in optimum selection of PCL–gelatin blend composition for biomedical applications. Furthermore, CO₂ solubility in polymers is restricted due to thermodynamic limitations but can be altered in the presence of a co-solvent to produce better foams. PCL can be foamed using supercritical CO₂. However, CO₂ foaming of PCL–gelatin blend becomes challenging to simultaneous swelling of PCL and compression of gelatin providing blend structural stability. This study has demonstrated ability of supercritical CO₂ to foam PCL–gelatin blends in presence of water to create porous structure. These foams were subjected post-fabrication crosslinking and supercritical CO₂ without losing porosity of foams. Thus, creating a strategy to use environmentally benign processes to fabricate, crosslink and impregnate porous scaffolds for biomedical applications.     

Influence of barium titanate nanofiller on PEO/PVdF-HFP blend-based polymer electrolyte membrane for Li-battery applications

Organic-inorganic hybrid membranes based on poly(ethylene oxide) (PEO) 6.25 wt%/poly(vinylidene fluoride hexa fluoro propylene) [P(VdF-HFP)] 18.75 wt% were prepared by using various concentration of nanosized barium titanate (BaTiO₃) filler. Structural characterizations were made by X-ray diffraction and Fourier transform infrared spectroscopy, which indicate the inclusion of BaTiO₃ in to the polymer matrix. Addition of filler creates an effective route of polymer-filler interface and promotes the ionic conductivity of the membranes. From the ionic conductivity results, 6 wt% of BaTiO₃-incorporated composite polymer electrolyte (CPE) showed the highest ionic conductivity (6 × 10^?3 Scm^?1 at room temperature). It is found that the filler content above 6 wt% rendered the membranes less conducting. Morphological images reveal that the ceramic filler was embedded over the membrane. Thermogravimetric and differential thermal analysis (TG-DTA) of the CPE sample with 6 wt% of the BaTiO₃ shows high thermal stability. Electrochemical performance of the composite polymer electrolyte was studied in LiFePO₄/CPE/Li coin cell. Charge-discharge cycle has been performed for the film exhibiting higher conductivity. These properties of the nanocomposite electrolyte are suitable for Li-batteries.     

Studies on freejets from radially lobed nozzles

The freejet characteristics of radially lobed nozzles were studied experimentally. Schlieren photographs of the freejets revealed that the lobes of the nozzles gave rise to alternate expansion-compression regions. For two of the lobed nozzles the potential core was reduced by a factor of three relative to the conical nozzle tested. The jet spread and the shear layer thickness of the lobed nozzles were considerably higher than those for the conical nozzle. The jet width and the shear layer thickness were higher in the major plane; however, the shear layer growth rate was higher in the minor plane of the lobed nozzles. Jet axial thrust measurements revealed a thrust loss of 14% for two of the lobed nozzles tested.     

Pulsatile flow between permeable beds

Pulsatile flow of a viscous fluid between two permeable beds is analyzed. The flow between and through the permeable beds are governed by the Navier-Stokes equations and Darcy's law, respectively. The velocity field and the volume flux are obtained for several cases and discussed. Further, when the permeability parameter k→0, the results agree with those of Wang (J. Appl. Mech. 38 (1971) 553).     

Synthesis of 6‐Fluoro‐7‐cyclic Amino‐substituted Dicarboxylic Acid Quinolones and their Antibacterial Activity

Novel 1‐carboxymethyl‐6‐fluoro‐7‐cyclic amino‐substituted‐4‐oxo‐1,4‐dihydroquinolone‐3‐carboxylic acids 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j , 7k , 7l , 7m , 7n were synthesized as a new class of quinolones. Ethyl‐6‐fluoro‐7‐chloro‐1,4‐dihydro‐4‐quinoline‐3‐carboxylic acid was prepared from conventional method and reacted with ethyl bromoacetate to furnish N‐carboxymethyl derivatives. The compounds were screed against various Gram‐positive and Gram‐negative bacterial strains. Antibacterial activity data is validated by molecular docking studies.     

Selective targeting of antibody conjugated multifunctional nanoclusters (nanoroses) to epidermal growth factor receptors in cancer cells

The ability of smaller than 100 nm antibody (Ab) nanoparticle conjugates to target and modulate the biology of specific cell types may enable major advancements in cellular imaging and therapy in cancer. A key challenge is to load a high degree of targeting, imaging, and therapeutic functionality into small, yet stable particles. A versatile method called thin autocatalytic growth on substrate (TAGs) has been developed in our previous study to form ultrathin and asymmetric gold coatings on iron oxide nanocluster cores producing exceptional near-infrared (NIR) absorbance. AlexaFluor 488 labeled Abs were used to correlate the number of Abs conjugated to iron oxide/gold nanoclusters (nanoroses) with the hydrodynamic size. A transition from submonolayer to multilayer aggregates of Abs on the nanorose surface was observed for 54 Abs and an overall particle diameter of ～60-65 nm. The hydrodynamic diameter indicated coverage of a monolayer of 54 Abs, in agreement with the prediction of a geometric model, by assuming a circular footprint of 16.9 nm diameter per Ab molecule. The targeting efficacy of nanoclusters conjugated with monoclonal Abs specific for epidermal growth factor receptor (EGFR) was evaluated in A431 cancer cells using dark field microscopy and atomic absorbance spectrometry (AAS) analysis. Intense NIR scattering was achieved from both high uptake of nanoclusters in cells and high intrinsic NIR absorbance of individual nanoclusters. Dual mode imaging with dark field reflectance microscopy and fluorescence microscopy indicates the Abs remained attached to the Au surfaces upon the uptake by the cancer cells. The ability to load intense multifunctionality, specifically strong NIR absorbance, conjugation of an Ab monolayer in addition to a strong r2 MRI contrast that was previously demonstrated in a total particle size of only 63 nm, is an important step forward in development of theranostic agents for combined molecular specific imaging and therapy.     

Membrane orientation of MSI-78 measured by sum frequency generation vibrational spectroscopy

Antimicrobial peptides (AMPs) selectively disrupt bacterial cell membranes to kill bacteria whereas they either do not or weakly interact with mammalian cells. The orientations of AMPs in lipid bilayers mimicking bacterial and mammalian cell membranes are related to their antimicrobial activity and selectivity. To understand the role of AMP-lipid interactions in the functional properties of AMPs better, we determined the membrane orientation of an AMP (MSI-78 or pexiganan) in various model membranes using sum frequency generation (SFG) vibrational spectroscopy. A solid-supported single 1,2-dipalmitoyl-an-glycero-3-[phospho-rac-(1-glycerol)] (DPPG) bilayer or 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (POPG) bilayer was used as a model bacterial cell membrane. A supported 1,2-dipalmitoyl-an-glycero-3-phosphocholine (DPPC) bilayer or a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer was used as a model mammalian cell membrane. Our SFG results indicate that the helical MSI-78 molecules are associated with the bilayer surface with ～70° deviation from the bilayer normal in the negatively charged gel-phase DPPG bilayer at 400 nM peptide concentration. However, when the concentration was increased to 600 nM, MSI-78 molecules changed their orientation to make a 25° tilt from the lipid bilayer normal whereas multiple orientations were observed for an even higher peptide concentration in agreement with toroidal-type pore formation as reported in a previous solid-state NMR study. In contrary, no interaction between MSI-78 and a zwitterionic DPPC bilayer was observed even at a much higher peptide concentration (～12,000 nM). These results demonstrate that SFG can provide insights into the antibacterial activity and selectivity of MSI-78. Interestingly, the peptide exhibits a concentration-dependent membrane orientation in the lamellar-phase POPG bilayer and was also found to induce toroidal-type pore formation. The deduced lipid flip-flop from SFG signals observed from lipids also supports MSI-78-induced toroidal-type pore formation.