Showing papers by "Nasser A.M. Barakat published in 2012"

Antibacterial activity and interaction mechanism of electrospun zinc-doped titania nanofibers

Abstract: In this study, a biological evaluation of the antimicrobial activity of Zn-doped titania nanofibers was carried out using Escherichia coli ATCC 52922 (Gram negative) and Staphylococcus aureus ATCC 29231 (Gram positive) as model organisms. The utilized Zn-doped titania nanofibers were prepared by the electrospinning of a sol–gel composed of zinc nitrate, titanium isopropoxide, and polyvinyl acetate; the obtained electrospun nanofibers were vacuum dried at 80°C and then calcined at 600°C. The physicochemical properties of the synthesized nanofibers were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis, thermogravimetry, and transmission electron microscopy (TEM). The antibacterial activity and the acting mechanism of Zn-doped titania nanofibers against bacteria were investigated by calculation of minimum inhibitory concentration and analyzing the morphology of the bacterial cells following the treatment with nanofibers solution. Our investigations reveal that the lowest concentration of Zn-doped titania nanofibers solution inhibiting the growth of S. aureus ATCC 29231 and E. coli ATCC 52922 strains is found to be 0.4 and 1.6 μg/ml, respectively. Furthermore, Bio-TEM analysis demonstrated that the exposure of the selected microbial strains to the nanofibers led to disruption of the cell membranes and leakage of the cytoplasm. In conclusion, the combined results suggested doping promotes antimicrobial effect; synthesized nanofibers possess a very large surface-to-volume ratio and may damage the structure of the bacterial cell membrane, as well as depress the activity of the membranous enzymes which cause bacteria to die in due course.

Titanium-based polymeric electrospun nanofiber mats as a novel organic semiconductor

Abstract: Organic semiconductors have been extensively used in the electronic devices as activate components. However, most of the introduced organic materials are structurally complicated which leads to high commercial production cost. In this study, thin layer from titanium isopropoxide/poly(vinyl acetate) electrospun nanofibers is introduced as a new class of semiconducting materials. Electrospinning as a simple, effective, high yield and low cost process was used to prepare the introduced nanofiber films. The obtained results indicated that the titanium isopropoxide content has a distinct influence on the electrical conductivity as increasing the content shifts the conduction mechanism toward the semiconducting behavior. At 40 and 50 wt% titanium isopropoxide, the nanofiber mats behave as a semiconductor. Within the ohmic region in the IV chart, the saturation current and the corresponding applied voltage are directly proportional to the titanium isopropoxide content. Leakage current study indicated that Schottky emission is the dominant mechanism through both of the negative and positive bias regions. The introduced titanium isopropoxide/poly (vinyl acetate) nanofiber mats might open a new avenue to utilize the metal alkoxide/polymer nanofibers as novel and effective type of semiconducting materials.

Synthesis and characterization of maghemite iron oxide (γ-Fe2O3) nanofibers: novel semiconductor with magnetic feature

Abstract: Among the reported nanostructural shapes, nanofibers have special interest due to the long axial ratio which has a distinct impact on many chemical and physical properties. In this study, synthesis of the desirable maghemite iron oxide (γ-Fe2O3) nanofibers is introduced. Calcination of electrospun mats composed of ferrous acetate and poly(vinyl alcohol) in argon atmosphere resulted in producing maghemite nanofibers. Detailed characterization affirmed that the obtained γ-Fe2O3 nanofibers are free of other iron oxides. Due to the axial ratio impact, the synthesized nanofibers which have an average diameter of ~70 nm do have magnetic properties resemble γ-Fe2O3 nanoparticles having an average diameter of ~5 nm. Accordingly, the produced nanofibers are considerable candidate for biomagnetic separation of the biomaterials. The prepared γ-Fe2O3 nanofibers can be easily handled as they were obtained in the form of strong mats. Electrical properties study indicated that the introduced nanofibers behave as a semiconducting material. Moreover, the synthesized γ-Fe2O3 nanofibers have band gap energy of ~4.2 eV. Based on the simplicity, effectiveness, high-yield, and low-cost features of the utilized preparation process and the studied physiochemical properties of the obtained product, the synthesized γ-Fe2O3 nanofibers might have considerable application fields.

A simple approach for synthesis, characterization and bioactivity of bovine bones to fabricate the polyurethane nanofiber containing hydroxyapatite nanoparticles

Abstract: In the present study, we had introduced polyurethane (PU) nanofibers that contain hydroxyapatite (HAp) nanoparticles (NPs) as a result of an electrospinning process. A simple method that does not depend on additional foreign chemicals had been employed to synthesize HAp NPs through the calcination of bovine bones. Typically, a colloidal gel consisting of HAp/PU had been electrospun to form nanofibers. In this communication, physiochemical aspects of prepared nanofibers were characterized by FE-SEM, TEM and TEM-EDS, which confirmed that nanofibers were well-oriented and good dispersion of HAp NPs, over the prepared nanofibers. Parameters, affecting the utilization of the prepared nanofibers in various nano-biotechnological fields have been studied; for instance, the bioactivity of the produced nanofiber mats was investigated while incubating in simulated body fluid (SBF). The results from incubation of nanofibers, indicated that incorporation of HAp strongly activates the precipitation of the apatite-like particles, because of the HAp NPs act as seed, that accelerate crystallization of the biological HAp from the utilized SBF.

Preparation, characterization, and cytotoxicity of CPT/Fe2O3-embedded PLGA ultrafine composite fibers: a synergistic approach to develop promising anticancer material

Abstract: The aim of this study was to fabricate camptothecin/iron(III) oxide (CPT/Fe₂O₃)-loaded poly(D,L-lactide-co-glycolide) (PLGA) composite mats to modulate the CPT release and to improve the structural integrity and antitumor activity of the released drug. The CPT/Fe₂O₃-loaded PLGA ultrafine fibers were prepared for the first time by electrospinning a composite solution of CPT/Fe₂O₃ and neat PLGA (4 weight percent). The physicochemical characterization of the electrospun composite mat was carried out by scanning electron microscopy, energy dispersive X-ray spectroscopy, electron probe microanalysis, thermogravimetry, transmission electron microscopy, ultraviolet-visible spectroscopy, and X-ray diffraction pattern. The medicated composite fibers were evaluated for their cytotoxicity on C2C12 cells using Cell Counting Kit-8 assay (Sigma-Aldrich Corporation, St Louis, MO). The in vitro studies indicated a slow and prolonged release over a period of 96 hours with mild initial burst. Scanning electron microscopy, thermogravimetry, and X-ray diffraction studies confirmed the interaction of CPT/Fe₂O₃ with the PLGA matrix and showed that the crystallinity of CPT decreased after loading. Incorporation of CPT in the polymer media affected both the morphology and the size of the CPT/Fe₂O₃-loaded PLGA composite fibers. Electron probe microanalysis and energy dispersive X-ray spectroscopy results confirmed well-oriented composite ultrafine fibers with good incorporation of CPT/Fe₂O₃. The cytotoxicity results illustrate that the pristine PLGA did not exhibit noteworthy cytotoxicity; conversely, the CPT/Fe₂O₃ composite fibers inhibited C2C12 cells significantly. Thus, the current work demonstrates that the CPT/Fe₂O₃-loaded PLGA composite fibers represent a promising chemotherapeutic system for enhancing anticancer drug efficacy and selectively targeting cancer cells in order to treat diverse cancers.

Novel CdPdS/PVAc core–shell nanofibers as an effective photocatalyst for organic pollutants degradation

Abstract: Photocorrosion and toxicity are the main constraints facing wide application of the CdS-based nanomaterials. In this study, CdS/PdS alloy is introduced as a core inside poly(vinyl acetate) (PVAc) nanofibers as a novel, efficient, reusable and easily recyclable photocatalyst. The core–shell structure was achieved using simple, effective and high yield technique: electrospinning. Typically, the CdS/PdS alloy was synthesized inside the polymer solution using cadmium acetate dihydrate, palladium acetate and ammonium sulfide precursors. Electrospinning of the obtained colloidal solution led to produce core–shell structure due to resultant water from formation of CdS/PdS reactions. The utilized physiochemical characterizations affirmed formation of the CdS/PdS alloy as well as the core–shell morphology. The obtained CdPdS–PVAc electrospun nanofibers exhibit good photocatalytic performance toward dye degradation. Two azo dyes, Reactive black 5 (RB5) and Reactive Orange 16 (RO16), were completely eliminated within very short time. Moreover, the photocatalytic efficiency was not affected after three consecutive cycles for both dyes. This solar-light-driven reusable CdPdS–PVAc hybrid mat photocatalyst can be easily applied for industrial application, especially in the open water surface.

Novel technique for polymeric nanofibers preparation: air jet spinning

Abstract: Although electrospinning is the most widely used nanofibers making technique due to its simplicity, low production rate and dependence on high voltage power supply are the main dilemmas. Moreover, completely non conductive polymers solutions cannot be electrospun which adds further constrain. In this study, we introduce a novel, safe and low cost technique to produce the polymeric nanofibers in ultrafast production rate. The proposed technique is based on exploiting the high speed air jets in stretching the polymer solution into ultrathin fibers. The average production rate of the proposed technique is around 15 mL/min. The diameter of the obtained nanofibers can be controlled easily by adjusting the polymer concentration and the distance between the nozzle and the collector. Interestingly, the nanofibers can be collected on solid and liquid collectors. Three polymers were examined in the introduced technique namely poly(lactic acid), poly(vinyl acetate) and polycaprolactone. The bioactivity of the Mg was strongly enhanced by utilizing the proposed technique to coat an Mg substrate by poly(lactic acid) nanofibers as a plenty of the bone-like precipitates was observed upon soaking of the coated samples for only one day in a simulated body fluid. Moreover, the corrosion resistance of the Mg substrate was highly improved after coating by using the introduced strategy. MC3T3 cells attachment and ingrowth were studied for the naked and coated Mg disk; the results were very satisfactory which further supports invoking the introduced strategy to coat the Mg-based hard tissues.

Activated carbon/silver-doped polyurethane electrospun nanofibers: Single mat for different pollutants treatment

Abstract: Adsorption ability and antibacterial activity could be created in a single electrospun nanofiber mat. Activated carbon/silver-doped polyurethane electrospun nanofiber mats have been introduced as a novel multifunction nanostructural material. Production of the introduced mat could be achieved by electrospinning of a colloidal solution from polyurethane containing activated carbon nanoparticles and silver nitrate. The high electric field and the presence of N,N-dimethylformamide, which is used as a solvent, led to reduced silver precursor in the silver nanoparticles. The introduced mat revealed good adsorption ability toward methylene blue dye. The presence of silver nanoparticles resulted in good antibacterial activity for the introduced mat since a piece of the mat could completely eliminate Escherichia coli bacteria. Overall, according to the utilized physiochemical characterizations, the introduced mat can be used as a mask or filter media.

Effect of silver-doping on the crystal structure, morphology and photocatalytic activity of TiO2 nanofibers

Abstract: In this study, effect of sliver-doping on the crystal structure, the nanofibrous morphology and the photocatalytic activity of titanium oxide nanofibers have been investigated. Silver-doped TiO2 nanofibers having different silver contents were prepared by calcination of electrospun nanofiber mats consisting of silver nitrate, titanium isopropoxide and poly(vinyl acetate) at 600 °C. The results affirmed formation of silver-doped TiO2 nanofibers composed of anatase and rutile when the silver nitrate content in the original electrospun solution was more than 3 wt%. The rutile phase content was directly proportional with the AgNO3 concentration in the electrospun solution. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that increase the silver content strongly enhances the dye oxidation process.