This is an editorial article. It has no abstract.
By combining LbL (layer-by-layer) self-assembly approach and host-guest interactions, a unique multilayer film was constructed and employed for a light-controlled drug release system. The drug molecules can be loaded and released into the resulting polyelectrolyte multilayers containing azobenzene (Azo) function groups by using the irradiation of visible light and UV light alternately. The photo-sensitivity of the multilayer films was studied through UV-vis spectrum, fluorescence spectrum and confocal microscopy. The target molecules could be rapidly released from the multilayers after 300 W UV light irradiation for 20 minutes. Moreover, they could be readsorbed into the multilayers uniformly when illuminated under the 300 W visible light for 10 minutes confirmed by the observation of confocal microscopy, and the readsorption ratio exceeds 100% evidenced from UV–vis spectroscopy. After several cycles of the above-mentioned process, the multilayer films show good fatigue resistance. All these results indicate the photo-sensitivity and high-efficiency of the multilayer films, which have great potential in controlled drug delivery platform and biomedical applications.
Effect of fibre spinning conditions on the electrical properties of cellulose and carbon nanotube composite fibres spun using ionic liquid as a benign solvent
C. Zhu, J. Chen, K. K. Koziol, J. W. Gilman, P. C. Trulove, S. S. Rahatekar
Vol. 8., No.3., Pages 154-163, 2014
Vol. 8., No.3., Pages 154-163, 2014
The aim of this study was to develop electrically conductive fibres from cellulose. To achieve this, the effect of fibre extrusion speed and fibre winding speed on the degree of alignment of multiwall carbon nanotubes (MWNTs), as well as the resulting electrical properties of the cellulose/MWNTs composite fibres were systematically studied. 1-Ethyl-3-Methylimidazolium Acetate (EMIMAc) was used as an environmentally benign solvent for dissolution of cellulose as well as for dispersion of MWNTs in the solution dope. To achieve good dispersion of MWNTs in the cellulose solution dope, MWNTs were non-covalently functionalized using carboxymethyl cellulose (CMC). This significantly improved the dispersion of MWNTs in the solution dope. The degree of alignment of MWNTs after both fibre extrusion and winding, was studied using scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). The degree of alignment of MWNTs was correlated with the electrical properties. A significant decrease in electrical conductivity accompanied the increase in degree of alignment of MWNTs when fibres were spun with higher extrusion speed. The decrease was also measured when fibres were spun with higher winding speed using a constant extrusion speed. However, the decrease in conductivity due to winding was low relative to fibres spun at highest extrusion speed.
Styrene-Acrylonitrile (SAN) copolymer has been blended to poly(methyl methacrylate) (PMMA) and to poly(butylene terephthalate) (PBT) to obtain polymer nanoblends based on thermodynamics and microrheological aspects. PMMA/SAN and SAN/PBT blends show miscibility windows for a specific range of acrylonitrile (AN) content in the SAN copolymer. The phase diagram for both blends has been calculated using the interaction energy density parameter B as function of AN content in the SAN. A critical interaction energy density parameter, Bcrit, was also calculated to find the miscibility window for both SAN blends. For some of the used SAN in the blends it was possible to obtain nanoblends as the AN content would allow B values close to the Bcrit. For immiscible PMMA/SAN and SAN/PBT blends the disperse particle size was predicted using suitable equations and it was observed by transmission electron microscopy (TEM). Acrylic copolymers were used as compatibilizer to modify the interfacial tension and reduce the disperse phase dimensions. The compatibilizer has shown strong effect by reducing the interfacial tension and by preventing the coalescence effect. The compatibilized blends have shown disperse particle size within the nanoscale.
Multiwalled carbon nanotubes (MWCNTs) based on bimetallic Co-Mo/MgO catalyst were produced in large scale by catalytic chemical vapor deposition method (CCVD) of methane. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Raman spectroscopy proved carbon nanotube (CNT) formation. As-produced multiwalled carbon nanotubes (PCNTs) and commercial ones (CCNTs) with the same diameter (10–20 nm) were melt blended with polyamide 6 (PA6). XRD patterns of nanocomposites showed applying 0.1% of both types of CNTs changed the crystalline structure of neat PA6 from α/γ form to thermodynamically more stable α-phase structure. Differential scanning calorimetry (DSC) showed both types of CNTs shifted crystallization temperature of about 10–15°C to higher temperature due to the nucleating effect of nanotubes. Furthermore, degree of crystallinity increased by about 30% in some composites, especially for PCNTs. Nanocomposites containing PCNTs exhibited improvements in thermal decomposition temperature in comparison with CCNT nanocomposites. Nanocomposites melt viscosity increased at high CNTs loading due to the filler-matrix entanglements.
Chelating resins are suitable materials for the removal of heavy metals in water treatments. A copolymer, Poly(MMA-co-MA), was synthesized by radical polymerization of maleic anhydride (MA) and methyl methacrylate (MMA), characterized and transformed into multifunctional nanochelating resin beads (80–150 nm) via hydrolysis, grafting and crosslink reactions. The resin beads were characterized by swelling studies, field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The main purpose of this work was to determine the adsorption capacity of the prepared resins (swelling ratio ~55%) towards metal ions such as Hg2+, Cd2+, Cu2+ from water at three different pH values (3, 6 and 9). Variations in pH and types of metal ions have not significantly affected the chelation capacity of these resins. The maximum chelation capacity of one of the prepared resin beads (Co-g-AP3) for Hg2+ was 63, 85.8 and 71.14 mg/g at pH 3, 6 and 9, respectively. Approximately 96% of the metal ions could be desorbed from the resin. Adsorption capacity of these resins towards three commercial synthetic azo dyes was also investigated. The maximum adsorption of dye AY42 was 91% for the resin Co-g-AP3 at room temperature. This insures the applicability of the synthesized resins for industrial applications.
Nanoparticles as drug delivery systems offer benefits such as protection of the encapsulated drug against degradation, site-specific targeting and prolonged blood circulation times. The aim of this study was to investigate nanoparticle uptake into Caco-2 cell monolayers, their co-localization within the lysosomal compartment and their cytotoxicity in different cell lines. Rhodamine-6G labelled poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles were prepared by a double emulsion solvent evaporation freeze-drying method. Uptake and co-localisation of PLGA nanoparticles in lysosomes were visualized by confocal laser scanning microscopy. The cytotoxicity of the nanoparticles was evaluated on different mammalian cells lines by means of Trypan blue exclusion and the MTS assay. The PLGA nanoparticles accumulated in the intercellular spaces of Caco-2 cell monolayers, but were also taken up transcellularly into the Caco-2 cells and partially co-localized within the lysosomal compartment indicating involvement of endocytosis during uptake. PLGA nanoparticles did not show cytotoxic effects in all three cell lines. Intact PLGA nanoparticles are therefore capable of moving across epithelial cell membranes partly by means of endocytosis without causing cytotoxic effects.
In this study, we compare the effects of aniline-modified mesoporous silica (AMS), raw silica (ARS) and nonmodified raw silica (NRS) particles on the physical properties of as-prepared polyaniline (PANI)-silica mesocomposites (PSM) and nanocomposites (PSN) and PANI-raw silica (PRSN) membranes. First, aniline-modified silica particles were synthesized by a conventional base-catalyzed sol-gel reaction of tetraethyl orthosilicate (TEOS) in the presence or absence of N-[3-(Trimethoxysilyl) propyl]aniline (PAPTMS). Subsequently, PSM, PSN and PRSN materials were prepared through in situ oxidation polymerization reaction of aniline monomer in the presence of AMS, ARS and NRS particles. It should be noted that all the properties of PSM membranes improved substantially from those of PSN and PRSN. For example, upon 3 wt% loading of AMS particles, 10, 25, 10, and 85% increases in thermal stability, mechanical strength, surface hydro - philicity and gas permeability were observed for PSM membranes, respectively, as well as more than 45% reduction in the thermal conductivity.