Photoluminescence of 2,4,6-tris[4-(phenylethynyl)phenyl]-1,3,5-triazines dispersed in polymer films

Photoluminescence of three types of 1,3,5-triazine derivatives with three kinds of diphenylacetylene side chains was investigated. They showed quantum yields higher than 46% in chloroform, and the Stokes shift (66–114 nm) in chloroform depended on the kind of the diphenylacetylene side chain. In cast films, the three compounds gave a larger Stokes shift of 132–211 nm, suggesting formation of an excimer in the solid. The 1,3,5-triazine derivatives were dispersed in films of polymers such as polystyrene and poly(vinyl acetate), and photoluminescence of the films containing the 1,3,5-triazine derivatives was investigated. Dispersion of the compound in a poly(vinyl acetate) film still gave a rather larger Stokes shift of 128–203 nm. In contrast, dispersion in polystyrene reduced the Stokes shift to about 60 nm, revealing an excellent dispersing effect of polystyrene for the compounds.     

Recyclable and stable silver deposited magnetic nanoparticles with poly (vinyl pyrrolidone)-catechol coated iron oxide for antimicrobial activity

This paper introduces a facile method to make highly stable and recyclable antimicrobial magnetic nanoparticles (NPs). Initially, magnetic iron oxide nanoparticles (IONPs) were coated with poly (vinyl pyrrolidone) conjugated catechol (PVP-CCDP). Afterward, silver nanoparticles (Ag⁰) were deposited onto PVP-CCDP coated IONPs using remain catechol. The prepared nanoparticles showed long term (~ 4 weeks) colloidal stability and redispersibility, respectively, against external magnetic field and over a broad range of pH (4–12). The NPs were characterized by UV–vis, SEM, XPS, and XRD measurements. TEM and DLS analyses showed that the mean particle size of PVP-CCDP coated IONPs/Ag⁰ were about 72 nm. The recyclable magnetic NPs possessed a high antibacterial effect against the model microbes Staphylococcus aureus and Escherichia coli and could be separated easily using magnet following antibacterial test for repeated uses and maintained 100% antibacterial efficiency during three cycles. In MTT assay, the magnetic nanoparticles possessed no measureable cytotoxicity to live cells.     

Hydrothermal synthesis and magnetic properties of CoS2 nano-octahedrons

Uniform single-crystalline CoS₂ nano-octahedrons have been prepared in high yield by a simple hydrothermal process. The octahedral structures exhibit a high geometric symmetry with smooth surfaces and the mean edge length is ~ 120 nm. X-ray diffraction, scanning electron microscopy, transmission electron microscopy were used to characterize the samples. Contrast experiments indicate that the capping agent poly(vinyl pyrrolidone) (PVP) and the complexing agent sodium citrate play important roles for the formation of octahedral CoS₂ nanostructures. A possible formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. Additionally, the magnetic properties of the CoS₂ nano-octahedrons were discussed in detail.     

Degradation of amoxicillin,ampicillin and cloxacillin antibiotics in aqueous solution by the UV/ZnO photocatalytic process

The study examined the effect of operating conditions (zinc oxide concentration, pH and irradiation time) of the UV/ZnO photocatalytic process on degradation of amoxicillin, ampicillin and cloxacillin in aqueous solution. pH has a great effect on amoxicillin, ampicillin and cloxacillin degradation. The optimum operating conditions for complete degradation of antibiotics in an aqueous solution containing 104, 105 and 103 mg/L amoxicillin, ampicillin and cloxacillin, respectively were: zinc oxide 0.5 g/L, irradiation time 180 min and pH 11. Under optimum operating conditions, complete degradation of amoxicillin, ampicillin and cloxacillin occurred and COD and DOC removal were 23.9 and 9.7%, respectively. The photocatalytic reactions under optimum conditions approximately followed a pseudo-first order kinetics with rate constant (k) 0.018, 0.015 and 0.029 min^?1 for amoxicillin, ampicillin and cloxacillin, respectively. UV/ZnO photocatalysis can be used for amoxicillin, ampicillin and cloxacillin degradation in aqueous solution.     

Sol–gel auto-combustion synthesis of PVP/CoFe2O4 nanocomposite and its magnetic characterization

Poly(vinyl pyrrolidone)/CoFe₂O₄ nanocomposite has been fabricated by a sol–gel auto-combustion method. Poly(vinyl pyrrolidone) was used as a reducing agent as well as a surface capping agent to prevent particle aggregation and stabilize the particles. The average crystallite size estimated from X-ray line profile fitting was found to be 20 ± 7 nm. The high field irreversibility and unsaturated magnetization behaviours indicate the presence of the core–shell structure in the sample. The exchange bias effect observed at 10 K suggests the existence of the magnetically aligned core surrounded by spin-disordered surface layer. The reduced remanent magnetization value of 0.6 at 10 K (higher than the theoretical value of 0.5) shows the PVP/CoFe₂O₄ nanocomposite to have cubic magnetocrystalline anisotropy according to the Stoner–Wohlfarth model.     

Template assisted synthesis of porous nanofibrous cellulose membranes for tissue engineering

Porous, nanofibrous bacterial cellulose (BC) membranes were produced by the bacterium Acetobacter xylinum. The bacterium was cultivated in an appropriate culture medium under static conditions. In situ pore formation was attained through the use of pin templates with diameters varying from 60 to 300 μm composed of polyestirene (ϕ = 300 μm) or optical fibers (ϕ = 60 μm), which were placed on culture medium with the pins immersed in the liquid. Cellulose biosynthesis occurred around the pins leaving tiny pores on the cellulose membrane. After removal of the template the biofilm was dried at 50 °C/24 h. Physico-chemical properties of BC membranes, like degree of crystallinity, swelling and tensile strength were not significantly altered after pore formation. Microstructure evaluation revealed that the film matrix is composed of long nanofibers isotropically distributed on its surface. Round-shaped pores with diameters varying between 60 and 300 μm, depending on the pin template used, were formed in the cellulose membranes. These pores exhibited no border failures that could start crack propagation along the film surface. Microporous membranes could be useful for applications in repairing tissues, which require high oxygenation rates or wound contracture delay.     

Transparent bacterial cellulose–boehmite–epoxi-siloxane nanocomposites

Organic–inorganic composite membranes were prepared from membranes of the bio-polymer bacterial cellulose (BC) and organic–inorganic sol composed of nanoparticulate boehmite and epoxi modified siloxane. Bacterial cellulose membranes are obtained in a highly hydrated state (1% cellulose and 99% cellulose) from cultures of Gluconacetobacter xylinus and could be used in the never-dried or in the dried state. Depending on the use of dried or never-dried BC membranes two main kinds of composites were obtained. In the first one dried BC membranes coated with the hybrid sol have lead to transparent membranes displaying a bi-phase structure where the two components could be easily distinguished, with individual structures preserved. A decrease was observed for tensile strength (50.5 MPa) and Young’s Modulus (2.8 GPa) when compared to pure BC membrane (112.5 MPa and 12.7 GPa). Elongation at break was observed to increase (2.5% against 1.5% observed for BC). When never-dried BC membranes were used transparent membranes were also obtained, however an improvement was observed for mechanical properties (tensile strength – 116 MPa and Young’s Modulus – 13.7 GPa). A lower value was obtained for the elongation at break (1.3%). In the last case the interaction between the two-phases lead to changes in the cellulose crystallinity as shown by X rays diffraction results. Multifunctional transparent membranes displaying the cellulose structure in one side and the boehmite–siloxane structure at the opposite face could find special applications in opto-electronics or biomedical areas taking advantage of the different chemical nature of the two components.     

Praseodymium analysis in aqueous solution by Pr3+–PVC membrane sensor based on N,N′-bis(4-hydroxysalicylidene)-1-3-phenylenediamine

A new Pr³⁺ poly vinyl chloride PVC membrane sensor based on a membrane containing 3% N,N′-bis(4-hydroxysalicylidene)-1-3-phenylenediamine (HSPDA) as an ionophore, 2% sodium tetraphenyl borate (NaTPB) as an anionic additive, 65% benzyl acetate (BA) as solvent mediator and 30% poly(vinyl chloride) was prepared. This sensor responds to praseodymium ion in a wide linear dynamic range of 1.0 × 10^?6 to 1.0 × 10^?2 mol L^?1 with Nernstian slope of 19.8 ± 0.4 mV per decade and a detection limit of 5.7 × 10^?7 mol L^? 1 in pH range of 3.1 to 9.8. It has a fast response time of ~5 s in the whole concentration range, and can be used for at least 2 months without any considerable divergences in the potentials. The proposed sensor displays an excellent selectivity for Pr³⁺ ions with respect to a large number of alkali, alkaline earth, transition and heavy metal ions. The developed sensor was successfully applied as an indicator electrode in Pr³⁺ ion potentiometric titration with EDTA, and in direct determination of fluoride ion in two mouth wash samples.     

Effects of process and source on elastic modulus of single cellulose fibrils evaluated by atomic force microscopy

A test method to measure cellulose fibril elastic modulus using atomic force microscopy was used to investigate the effects of process and source on the moduli of single cellulose fibrils. The cellulose fibrils were generated from cellulose by mechanical treatments. Individual fibrils were suspended over a micro scale groove etched on a silicon wafer. A nano-scale three-point bending test was performed to obtain the elastic moduli. The results indicated that the elastic moduli of cellulose fibrils were not significantly different between 30 min and 60 min of high intensity ultrasonic treatment for Lyocell fiber, between isolation methods of ultrasonic and homogenizer treatment for pure cellulose fiber, and between different cellulose sources of pulp fibers treated by homogenizer regardless the effects of sample size coupled with inherent variation in the raw material. The elastic modulus of Lyocell fibrils with diameters from 150 to 180 nm was evaluated to be 98 ± 6 GPa. Modulus values decreased dramatically when the diameter was more than 180 nm.     

Strong and optically transparent biocomposites reinforced with cellulose nanofibers isolated from peanut shell

Cellulose nanofibers–reinforced PVA biocomposites were prepared from peanut shell by chemical–mechanical treatments and impregnation method. The composite films were optically transparent and flexible, showed high mechanical and thermal properties. FE-SEM images showed that the isolated fibrous fragments had highly uniform diameters in the range of 15–50 nm and formed fine network structure, which is a guarantee of the transparency of biocomposites. Compared to that of pure PVA resin, the modulus and tensile strength of prepared nanocomposites increased from 0.6 GPa to 6.0 GPa and from 31 MPa to 125 MPa respectively with the fiber content as high as 80 wt%, while the light transmission of the composite only decreased 7% at a 600 nm wavelength. Furthermore, the composites exhibited excellent thermal properties with CTE as low as 19.1 ppm/K. These favorable properties indicated the high reinforcing efficiency of the cellulose nanofibers isolated from peanut shell in PVA composites.     

Porous poly(vinyl alcohol)/sepiolite bone scaffolds: Preparation,structure and mechanical properties

Porous poly(vinyl alcohol) (PVA)/sepiolite nanocomposite scaffolds containing 0–10 wt.% sepiolite were prepared by freeze-drying and thermally crosslinked with poly(arylic acid). The microstructure of the obtained scaffolds was characterised by scanning electron microscopy and micro-computed tomography, which showed a ribbon and ladder like interconnected structure. The incorporation of sepiolite increased the mean pore size and porosity of the PVA scaffold as well as the degree of anisotropy due to its fibrous structure. The tensile strength, modulus and energy at break of the PVA solid material that constructed the scaffold were found to improve with additions of sepiolite by up to 104%, 331% and 22% for 6 wt.% clay. Such enhancements were attributed to the strong interactions between the PVA and sepiolite, the good dispersion of sepiolite nanofibres in the matrix and the intrinsic properties of the nanofibres. However, the tensile properties of the PVA scaffold deteriorated in the presence of sepiolite because of the higher porosity, pore size and degree of anisotropy. The PVA/sepiolite nanocomposite scaffold containing 6 wt.% sepiolite was characterised by an interconnected structure, a porosity of 89.5% and a mean pore size of 79 μm and exhibited a tensile strength of 0.44 MPa and modulus of 14.9 MPa, which demonstrates potential for this type of materials to be further developed as bone scaffolds.     

Electrospun composites of PHBV,silk fibroin and nano-hydroxyapatite for bone tissue engineering

Electrospinning of fibrous scaffolds containing nano-hydroxyapatite (nHAp) embedded in a matrix of functional biomacromolecules offers an attractive route to mimicking the natural bone tissue architecture. Functional fibrous substrates will support cell attachment, proliferation and differentiation, while the role of HAp is to induce cells to secrete extracellular matrix (ECM) for mineralization to form bone. Electrospinning of biomaterials composed of polyhydroxybutyrate-co-(3-hydroxyvalerate) with 2% valerate fraction (PHBV), nano-hydroxyapatite (nHAp), and Bombyx mori silk fibroin essence (SF), Mw = 90KDa, has been achieved for nHAp and SF solution concentrations of 2 (w/vol) % each and 5 (w/vol) % each. The structure and properties of the nanocomposite fibrous membranes were investigated by means of Scanning Electron Microscopy in combination with Energy Dispersive X-Ray Analysis (SEM/EDX), Fourier Transformed Infrared Spectroscopy (FT-IR), uniaxial tensile and compressive mechanical testing, degradation tests and in vitro bioactivity tests. SEM images showed smooth, uniform and continuous fibre deposition with no bead formation, and fibre diameters of between 10 and 15 μm. EDX and FT-IR confirmed the presence of nHAp and SF. After one month in deionised water, tests showed less than 2% weight loss with the samples retaining their fibrous morphology, confirming that this material biodegrades slowly. After 28 days of immersion in Simulated Body Fluid (SBF) an apatite layer was visible on the surface of the fibres, proving their bioactivity. Preliminary in vitro biological assessment showed that after 1 and 3 days in culture, cells were attached to the fibres, retaining their morphology while presenting a flattened appearance and elongated shape on the surface of fibres. Young's modulus was found to increase from 0.7 kPa (± 0.33 kPa) for electrospun samples of PHBV only to 1.4 kPa (± 0.54 kPa) for samples with 2 (w/vol) % each of nHAp and SF. Samples prepared with 5 (w/vol) % each of nHAp and SF did not show a similar improvement.     

Poly(vinyl alcohol)–hydroxyapatite biomimetic scaffold for tissue regeneration

Hydroxyapatite–poly(vinyl alcohol) composite blocks were produced by freeze–thawing in situ synthesized hybrid suspension. Matrix mediated precipitation of hydroxyapatite particles in the polymer, controlled the particle size in nanometer range (< 100 nm) and hydrogelation induced an ordered three-dimensional assembly of the particles. Morphological and crystallographic characterization revealed the formation of a macro-porous hydroxyapatite–poly(vinyl alcohol) nanocomposite block. Initial results indicate compositional dependence of modulus of elasticity of the composite.     

Reactive compatibilization of composites of ethylene–vinyl acetate copolymers with cellulose fibres

Composites based on ethylene–vinyl acetate copolymers (EVA) functionalised with reactive groups (maleic anhydride, glycidyl methacrylate) and cellulose fibres (Cell) of different type were obtained by melt mixing, in the composition range 0–50 wt% Cell. The phase behaviour, the morphology and matrix–fibre interactions of the composites were analysed by DSC, DMTA, TGA, SEM and FT-IR spectroscopy. FT-IR analysis indicated the chemical interactions between the functional groups (MA, GMA) of EVA and the hydroxyl groups of cellulose. Accordingly, SEM microscopy pointed out an improved adhesion between cellulose and matrix in both EVA–MA/Cell and EVA–GMA/Cell composites, as compared to EVA/Cell composites. Glass transition behaviour and filler effectiveness (C_FE) were analysed by DMTA. T_g of EVA and EVA–GMA changed markedly by the incorporation of cellulose. Cellulose was found to be more effective filler for EVA–GMA (C_FE = 0.02) than EVA–MA (C_FE = 0.22). Thermal resistance and tensile properties were significantly improved for GMA functionalised systems.     

Thermal and dynamic mechanical properties of grafted kenaf filled poly (vinyl chloride)/ethylene vinyl acetate composites

The effects of kenaf and poly (methyl methacrylate grafted kenaf on the thermal and dynamic mechanical properties of poly (vinyl chloride), PVC and ethylene vinyl acetate, EVA blends were investigated. The PVC/EVA/kenaf composites were prepared by mixing the grafted and ungrafted kenaf fiber and PVC/EVA blend using HAAKE Rheomixer at a temperature of 150 °C and the rotor speed at 50 rpm for 20 min. The composites were subjected to Differential Scanning Calorimetric (DSC), Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) and Scanning Electron Microscopy (SEM) studies. The DSC data revealed that the crystallinity of the EVA decreased with the addition of 30% grafted and ungrafted kenaf fibers. TGA and derivative thermogravimetric (DTG) curves displayed an increase in the thermal stability of the composites upon grafting of the fiber. Studies on DMA indicate that the T_g of the PVC and EVA in the PVC/EVA/kenaf composites has been shifted to higher temperature with the addition of the kenaf fiber. The presence of PMMA on the surface of grafted kenaf fiber was further confirmed by the analytical results from FTIR. The morphology of fractured surfaces of the composites, which was examined by a scanning electron microscope, showed the adhesion between the kenaf fiber and the PVC/EVA matrix was improved upon grafting of the kenaf fiber.     

Release of Ftorafur from pH-sensitive hydrogels with hyperbranched poly(4-vinylbenzyl chloride) moieties

Drug release behavior of a hydrogel is related to its transport mechanism, which is dominated by structure of the hydrogel. Therefore, we prepared pH-sensitive poly(4-vinylpyridine) (P4VP) hydrogels with hyperbranched poly(4-vinylbenzyl chloride) (PVBC; M_n = 2391 g/mol, PDI = 1.87, the minimum percent linearity = 12.4%) moieties (P4VP-PVBC) by atom transfer radical polymerizations (ATRP) in two steps. A PVBC moiety provides the hydrogel with a microenvironment, which may encapsulate guest molecules like drug. The presence of the microenvironment could affect drug transport in the hydrogel matrices. To understand this, we used Ftorafur as drug molecule, and investigated release behavior of the P4VP-based hydrogels. Diffusion and transport mechanism of Ftorafur in the P4VP-based hydrogels was analyzed by early-time and late-time approximation diffusion coefficients. It was found that the transport behavior of Ftorafur was related to the presence of the PVBC moiety and external pH. The presence of the PVBC moiety could sustain release of Ftorafur.     

Mechanical properties,urea diffusion,and cell cultural response of poly(vinyl alcohol)–Chitosan bioartificial membranes via molecular modelling and experimental investigation

An in silico protocol jointly with experimental approach is here used to design and investigate poly(vinyl alcohol) (PVA)–Chitosan polymer membranes. Atomistic computational investigations were performed to assess mechanical behaviour and urea molecules diffusion of PVA–Chitosan blend bulk models with different compositions. Blend membranes of PVA–Chitosan were prepared with different compositions by solvent-casting technique and their swelling behaviour, morphological, mechanical and transport properties were investigated. Cytotoxicity assessments by means of in vitro, indirect contact assay were carried using L929 fibroblast-like cells. The values of the Young modulus along the three perpendicular directions of computational systems were very similar and ranged from 3.64 to 4.39 GPa. Urea diffusivity was related to the blends composition and the values ranged from 1.62 × 10^?7 to 9.56 × 10^?8 cm²/s. Overall, a good agreement was found between experimental and simulation data.     

Polyetherurethaneurea reinforced poly(vinyl alcohol) dialysis membranes: studies on permeability and mechanical strength

Poly(vinyl alcohol) is a hydrogel which is extensively studied for a variety of biomedical applications. Membranes developed from crosslinked poly(vinyl alcohol) (PVA) is having excellent permeability to solutes. However its wet breaking strength is low. Polyetherurethaneurea (PEUU), having an excellent mechanical strength is blended with PVA as a reinforcement, and membranes developed are studied for its permeability and mechanical strength. The optimum membrane selected, is having permeability and wet breaking strength almost equal to the commercially available cellulose acetate membrane.     

Novel phosphate glasses with different amounts of TiO2 for biomedical applications: Dissolution tests and proof of concept of fibre drawing

The aim of this work was to develop a range of phosphate glasses having different solubilities and with suitable characteristics to be drawn into fibres. Three glasses with molar compositions 50P₂O₅–30CaO–9Na₂O–3SiO₂–3MgO–(5 ? x)K₂O–xTiO₂ (x = 0, 2.5, 5) were prepared and characterized in terms of thermal properties, density and dissolution rate. The dissolution tests were conducted in bi-distilled water (pH 6.0 ± 0.5), Tris–HCl (pH 7.4 ± 0.1) and citric acid buffer solutions (pH 3.0 ± 0.1) in order to study the influence of pH on the dissolution process.TiO₂ had a stabilizing effect on the glass, causing an increase in the glass transition temperature and density and a decrease in the glass dissolution rate. Acidic medium was found to strongly enhance the glass dissolution. The pH decrease caused by the acidic degradation products and the consequent enhancement of the glass weight loss were attenuated with the TiO₂ increase.The fabrication of glass fibres using a preform drawing approach was investigated. Control and versatility of the process are demonstrated through the production of several tens of meters of fibre with diameters ranging from 37 ± 2 μm up to 173 ± 7 μm. Preliminary analysis reveal pristine fibres, free of crystallization, showing adequate flexibility for prospective biomedical applications.     

The influence of operating parameters on the drug release and anti-bacterial performances of alginate wound dressings prepared by three-dimensional plotting

Three-dimensional plotting was used to manufacture fibrous alginate hydrogel wound dressings. Samples manufactured using varied operating parameters (increased air pressure, nozzle diameter, and layer increment or decreased calcium concentration, alginate concentration, and speed of the nozzle in the x and y directions) were compared to the control samples. The changes in the fiber size, porosity, tensile properties, degradation, swelling ratio, tetracycline release efficacy, water vapor transmission rate (WVTR), and bacterial inhibition potential due to alterations of the operating parameters were measured. The samples manufactured using altered operating parameters had larger fiber sizes and were less porous than the controls (p < 0.05). A significantly higher Young's modulus, a larger ultimate tensile strength, less degradation, and lower swelling ratios were also found among some of the altered samples (p < 0.05). The tetracycline release efficacies and bacterial inhibition potentials of the altered samples were not found to be significantly different from those of the controls. The WVTRs of most samples were slightly lower than those of common commercial dressings. When compared to films, the fibrous samples were able to absorb liquid faster and were less stiff, allowing for better conformation to the contours of the wounds. The fibrous samples also provided more sustained tetracycline release.