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issn:1388-0.64
1.  The novel albumin–chitosan core–shell nanoparticles for gene delivery: preparation, optimization and cell uptake investigation 
Natural polymers and proteins such as chitosan (CS) and albumin (Alb) have recently attracted much attention both in drug delivery and gene delivery. The underlying rationale is their unique properties such as biodegradability, biocompatibility and controlled release. This study aimed to prepare novel albumin–chitosan–DNA (Alb-CS-DNA) core–shell nanoparticles as a plasmid delivery system and find the best conditions for their preparation. Phase separation method and ionic interaction were used for preparation of Alb nanoparticles and Alb-CS-DNA core–shell nanoparticles, respectively. The effects of three important independent variables (1) CS/Alb mass ratio, (2) the ratios of moles of the amine groups of cationic polymers to those of the phosphate groups of DNA (N/P ratio), and (3) Alb concentration, on the nanoparticle size and loading efficiency of the plasmid were investigated and optimized through Box–Behnken design of response surface methodology (RSM). The optimum conditions were found to be CS/Alb mass ratio = 3, N/P ratio = 8.24 and Alb concentration = 0.1 mg/mL. The most critical factors for the size of nanoparticles and loading efficiency were Alb concentration and N/P ratio. The optimized nanoparticles had an average size of 176 ± 3.4 nm and loading efficiency of 80 ± 3.9 %. Cytotoxicity experiments demonstrated that the prepared nanoparticles were not toxic. The high cellular uptake of nanoparticles (~85 %) was shown by flow cytometry and fluorescent microscopy.
doi:10.1007/s11051-013-1651-0
PMCID: PMC3868460  PMID: 24363607
Albumin; Chitosan; Nanoparticle; Gene delivery; Optimization
2.  Gravity-induced swirl of nanoparticles in microfluidics 
Parallel flows of two fluids in microfluidic devices are used for miniaturized chemistry, physics, biology and bioengineering studies, and the streams are often considered to remain parallel. However, as the two fluids do not always have the same density, interface reorientation induced by density stratification is unavoidable. In this paper, flow characteristics of an aqueous polystyrene nanofluid and a sucrose-densified aqueous solution flowing parallel in microchannels are examined. Nanoparticles 100 nm in diameter are used in the study. The motion of the nanoparticles is simulated using the Lagrangian description and directly observed by a confocal microscope. Matched results are obtained from computational and empirical analysis. Although solution density homogenizes rapidly resulting from a fast diffusion of sucrose in water, the nanofluid is observed to rotate for an extended period. Angular displacement of the nanofluid depends on the ratio of gravitational force to viscous force, Re/Fr2, where Re is the Reynolds number and Fr is the Froude number. In the developing region at the steady state, the angular displacement is related to y/Dh, the ratio between distance from the inlet and the hydraulic diameter of the microfluidic channel. The development of nanofluid flow feature also depends on h/w, the ratio of microfluidic channel’s height to width. The quantitative description of the angular displacement of nanofluid will aid rational designs of microfluidic devices utilizing multistream, multiphase flows.
doi:10.1007/s11051-013-1611-8
PMCID: PMC3927913  PMID: 24563612
Microfluidics; Density stratification; Nanoparticles; Angular displacement; Miscible fluids
3.  Acoustic wave in a suspension of magnetic nanoparticle with sodium oleate coating 
The ultrasonic propagation in the water-based magnetic fluid with doubled layered surfactant shell was studied. The measurements were carried out both in the presence as well as in the absence of the external magnetic field. The thickness of the surfactant shell was evaluated by comparing the mean size of magnetic grain extracted from magnetization curve with the mean hydrodynamic diameter obtained from differential centrifugal sedimentation method. The thickness of surfactant shell was used to estimate volume fraction of the particle aggregates consisted of magnetite grain and surfactant layer. From the ultrasonic velocity measurements in the absence of the applied magnetic field, the adiabatic compressibility of the particle aggregates was determined. In the external magnetic field, the magnetic fluid studied in this article becomes acoustically anisotropic, i.e., velocity and attenuation of the ultrasonic wave depend on the angle between the wave vector and the direction of the magnetic field. The results of the ultrasonic measurements in the external magnetic field were compared with the hydrodynamic theory of Ovchinnikov and Sokolov (velocity) and with the internal chain dynamics model of Shliomis, Mond and Morozov (attenuation).
doi:10.1007/s11051-014-2271-z
PMCID: PMC3955142  PMID: 24672282
Nanoparticles; Magnetic fluid; Velocity and absorption of ultrasound; Hydrodynamic size
4.  Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films 
In this work, we present the temperature-dependence and time-resolved photoluminescence (PL) of CdS nanoparticles capped independently with three different ligands thiophenol, thioglycerol, and l-cysteine over a broad temperature range from 10 to 300 K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2 nm as determined from X-ray diffraction (XRD). From the analysis of AFM images, it was found that the lateral particle sizes of capped CdS nanoparticles are greater than those deduced from XRD or optical absorption measurements. The aim of this study is the investigation of the impact of the organic ligands on the radiative recombination dynamics in organically capped CdS nanoparticles. From the PL study and based on the temperature-dependence and time-resolved emission spectroscopy, we conclude that the emission of CdS QDs film originates from recombination of the delocalized carriers in the internal core states with a small contribution of the localized carriers at the interface. The PL decay reveals a biexponential behavior for the entire three samples at all temperatures. One of the two exponential components decays rapidly with a time τ1 in the range 0.5–0.8 ns, whereas the other decays much more slowly, with a time τ2 in the range 1–3 ns. The weak activation energy (32–37 meV) deduced from the temperature dependence of the PL intensity suggests the involvement of shallow traps. The analysis of the experimental results reveals a relatively narrow size distribution, an efficient surface passivation, and a satisfactory thermal stability of CdS nanocrystals.
doi:10.1007/s11051-013-2242-9
PMCID: PMC3925497  PMID: 24563613
Organic ligands; CdS nanoparticles; Time-correlated single photon counting; Radiative recombination; Temperature; Surface states; Nanostructure; Optics
5.  Non-thermal plasma-driven synthesis of Eu3+:Y2O3 nanosized phosphors 
The synthesis of nanosized phosphors by using the non-thermal plasma-driven method is presented. The method allows to control the average grain size of nanocrystals. The synthesis of Eu3+-doped Y2O3 nanocrystalline phosphors at water solution of nitrates is described. The average sizes of nanocrystals were controlled by sintering temperature. Their structure, morphology, and luminescent properties were investigated.
doi:10.1007/s11051-013-2176-2
PMCID: PMC3890610  PMID: 24453571
Nanocrystallites; Plasma; Rare earths (RE); Luminescence
6.  Occupational safety and health criteria for responsible development of nanotechnology 
Organizations around the world have called for the responsible development of nanotechnology. The goals of this approach are to emphasize the importance of considering and controlling the potential adverse impacts of nanotechnology in order to develop its capabilities and benefits. A primary area of concern is the potential adverse impact on workers, since they are the first people in society who are exposed to the potential hazards of nanotechnology. Occupational safety and health criteria for defining what constitutes responsible development of nanotechnology are needed. This article presents five criterion actions that should be practiced by decision–makers at the business and societal levels—if nanotechnology is to be developed responsibly. These include (1) anticipate, identify, and track potentially hazardous nanomaterials in the workplace; (2) assess workers’ exposures to nanomaterials; (3) assess and communicate hazards and risks to workers; (4) manage occupational safety and health risks; and (5) foster the safe development of nanotechnology and realization of its societal and commercial benefits. All these criteria are necessary for responsible development to occur. Since it is early in the commercialization of nanotechnology, there are still many unknowns and concerns about nanomaterials. Therefore, it is prudent to treat them as potentially hazardous until sufficient toxicology, and exposure data are gathered for nanomaterial-specific hazard and risk assessments. In this emergent period, it is necessary to be clear about the extent of uncertainty and the need for prudent actions.
doi:10.1007/s11051-013-2153-9
PMCID: PMC3890581  PMID: 24482607
Risk assessment; Ethics; Risk management; Regulation; Toxicology; Environmental and health effects
7.  Effect of silica nanoparticles on clay swelling and aqueous stability of nanoparticle dispersions 
The results of the effects of electrolyte type and concentration, nanoparticle concentration, pH, and temperature on the mobility and aqueous stability of polyethylene glycol (PEG)-coated silica nanoparticles are presented. Nanoparticle mobility was evaluated based on the ability to inhibit montmorillonite swelling in aqueous solutions through visual swelling tests, and the results were quantified in terms of the swelling index. The presence of PEG-coated silica nanoparticles was found to have a positive influence on the inhibition of clay swelling only in the presence of electrolytes. Quantification of nanoparticle stability in the presence of montmorillonite particles was achieved using ultraviolet–visible (UV–vis) spectrophotometry. At the highest concentration of montmorillonite dispersion studied, interaction between the dispersed montmorillonite particles and PEG-coated silica nanoparticles resulted in nanoparticle aggregation as indicated by increased turbidity and absorbance readings. Both nanoparticle concentration and montmorillonite dispersion concentration, in addition to the presence and concentration of NaCl, were found to strongly influence the stability of the mixture.
doi:10.1007/s11051-013-2137-9
PMCID: PMC3890561  PMID: 24482606
Nanoparticles; Montmorillonite clay; Polyethylene glycol (PEG); Swelling; Aqueous stability; Mobility; Coating; Oil recovery
8.  Effects of the physicochemical properties of titanium dioxide nanoparticles, commonly used as sun protection agents, on microvascular endothelial cells 
Until now, the potential effects of titanium dioxide (TiO2) nanoparticles on endothelial cells are not well understood, despite their already wide usage. Therefore, the present work characterizes six TiO2 nanoparticle samples in the size range of 19 × 17 to 87 × 13 nm, which are commonly present in sun protection agents with respect to their physicochemical properties (size, shape, ζ-potential, agglomeration, sedimentation, surface coating, and surface area), their interactions with serum proteins and biological impact on human microvascular endothelial cells (relative cellular dehydrogenase activity, adenosine triphosphate content, and monocyte chemoattractant protein-1 release). We observed no association of nanoparticle morphology with the agglomeration and sedimentation behavior and no variations of the ζ-potential (−14 to −19 mV) in dependence on the surface coating. In general, the impact on endothelial cells was low and only detectable at concentrations of 100 μg/ml. Particles containing a rutile core and having rod-like shape had a stronger effect on cell metabolism than those with anatase core and elliptical shape (relative cellular dehydrogenase activity after 72 h: 60 vs. 90 %). Besides the morphology, the nanoparticle shell constitution was found to influence the metabolic activity of the cells. Upon cellular uptake, the nanoparticles were localized perinuclearly. Considering that in the in vivo situation endothelial cells would come in contact with considerably lower nanoparticle amounts than the lowest-observable adverse effects level (100 μg/ml), TiO2 nanoparticles can be considered as rather harmless to humans under the investigated conditions.
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-013-2130-3) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-013-2130-3
PMCID: PMC3890566  PMID: 24482605
Endothelial cells; Environmental and health effects; Nanoparticle; Nanotoxicology; Sun protection agent; Titanium dioxide
9.  A facile route to synthesize nanogels doped with silver nanoparticles 
In this work, we describe a simple method to prepare hybrid nanogels consisting of a biocompatible core-shell polymer host containing silver nanoparticles. First, the nanogels (NG, ~160 nm) containing a lysozyme rich core and a dextran rich shell, are prepared via Maillard and heat-gelation reactions. Second, silver nanoparticles (Ag NPs, ~5nm) are synthesized in situ in the NG solution without requiring additional reducing agents. This approach leads to stable Ag NPs located in the NG. Furthermore, we demonstrate that the amount of Ag NPs in the NG can be tuned by varying silver precursor concentration. Hybrid nanogels with silver nanoparticles have potential in antimicrobial, optical and therapeutic applications.
doi:10.1007/s11051-012-1323-5
PMCID: PMC3583544  PMID: 23459266
dextran; lysozyme; nanogel; silver nanoparticles
10.  Nanoparticles influence droplet formation in a T-shaped microfluidic 
Droplet formation in the presence of nanoparticles was studied in a T-shaped microfluidic device numerically. Nanoparticles in continuous phase did not influence droplet formation dynamics obviously. Contrarily, the presence of nanoparticles in dispersed phase will influence evidently droplet formation dynamics, likely reasons are the accumulation of nanoparticles at the liquid–liquid interface leading to the variation of interfacial tension and the anisotropy of nanoparticles’ movement at interface. The droplet size decreases almost linearly with increasing of the volume fraction of nanoparticles in dispersed phase when the volume fraction of nanoparticles not exceeding a critical value (about 0.2 %), because very high concentration of nanoparticles results in particle aggregation so as to not decrease interfacial tension so obviously any more. A complicated mechanism of temperature influences on droplet formation may exist combining the variations of effective viscosity and interfacial tension. Discussions on microscopic mechanism of droplet formation in the presence of nanoparticles were carried out.
doi:10.1007/s11051-013-2128-x
PMCID: PMC3853645  PMID: 24339728
Droplet formation; Nanoparticles; T-shaped microfluidic; Numerical simulation; Fluid dynamics
11.  Interlaboratory comparison of size measurements on nanoparticles using nanoparticle tracking analysis (NTA) 
One of the key challenges in the field of nanoparticle (NP) analysis is in producing reliable and reproducible characterisation data for nanomaterials. This study looks at the reproducibility using a relatively new, but rapidly adopted, technique, Nanoparticle Tracking Analysis (NTA) on a range of particle sizes and materials in several different media. It describes the protocol development and presents both the data and analysis of results obtained from 12 laboratories, mostly based in Europe, who are primarily QualityNano members. QualityNano is an EU FP7 funded Research Infrastructure that integrates 28 European analytical and experimental facilities in nanotechnology, medicine and natural sciences with the goal of developing and implementing best practice and quality in all aspects of nanosafety assessment. This study looks at both the development of the protocol and how this leads to highly reproducible results amongst participants. In this study, the parameter being measured is the modal particle size.
doi:10.1007/s11051-013-2101-8
PMCID: PMC3857864  PMID: 24348090
Nanoparticle; Interlaboratory comparison; Reproducibility; Polydispersity; Toxicology; Health and safety implications
12.  Development of novel anti-Kv 11.1 antibody-conjugated PEG–TiO2 nanoparticles for targeting pancreatic ductal adenocarcinoma cells 
Titanium dioxide (TiO2) has been widely used in many nanotechnology areas including nanomedicine, where it could be proposed for the photodynamic and sonodynamic cancer therapies. However, TiO2 nanoformulations have been shown to be toxic for living cells. In this article, we report the development of a new delivery system, based on nontoxic TiO2 nanoparticles, further conjugated with a monoclonal antibody against a novel and easily accessible tumor marker, e.g., the Kv 11.1 potassium channel. We synthesized, by simple solvothermal method, dicarboxylic acid-terminated PEG TiO2 nanocrystals (PEG–TiO2 NPs). Anti-Kv 11.1 monoclonal antibodies (Kv 11.1-Mab) were further linked to the terminal carboxylic acid groups. Proper conjugation was confirmed by X-ray photoelectron spectroscopy analysis. Kv 11.1-Mab-PEG–TiO2 NPs efficiently recognized the specific Kv 11.1 antigen, both in vitro and in pancreatic ductal adenocarcinoma (PDAC) cells, which express the Kv 11.1 channel onto the plasma membrane. Both PEG TiO2 and Kv 11.1-Mab-PEG–TiO2 NPs were not cytotoxic, but only Kv 11.1-Mab-PEG–TiO2 NPs were efficiently internalized into PDAC cells. Data gathered from this study may have further applications for the chemical design of nanostructures to be applied for therapeutic purposes in pancreatic cancer.
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-013-2111-6) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-013-2111-6
PMCID: PMC3857862  PMID: 24348091
Nanoparticles; PEG–TiO2; XPS analysis; Kv 11.1; Pancreatic cancer; Nanomedicine
13.  Nanomaterial inhalation exposure from nanotechnology-based cosmetic powders: a quantitative assessment 
In this study we quantified exposures to airborne particles ranging from 14 nm to 20 µm due to the use of nanotechnology-based cosmetic powders. Three nanotechnology-based and three regular cosmetic powders were realistically applied to a mannequin’s face while measuring the concentration and size distribution of inhaled aerosol particles. Using these data we calculated that the highest inhaled particle mass was in the coarse aerosol fraction (2.5–10 µm), while particles <100 nm made minimal contribution to the inhaled particle mass. For all powders, 85–93 % of aerosol deposition occurred in the head airways, while <10 % deposited in the alveolar and <5 % in the tracheobronchial regions. Electron microscopy data suggest that nanomaterials were likely distributed as agglomerates across the entire investigated aerosol size range (14 nm–20 µm). Thus, investigation of nanoparticle health effects should consider not only the alveolar region, but also other respiratory system regions where substantial nanomaterial deposition during the actual nanotechnology-based product use would occur.
doi:10.1007/s11051-012-1229-2
PMCID: PMC3500971  PMID: 23175627
Nanoaerosol; Consumer products; Nanoparticles; Personal exposure; Safety of nanotechnology
14.  Functionalized NaA nanozeolites labeled with 224,225Ra for targeted alpha therapy 
The 223Ra, 224Ra, and 225Ra radioisotopes exhibit very attractive nuclear properties for application in radionuclide therapy. Unfortunately the lack of appropriate bifunctional ligand for radium is the reason why these radionuclides have not found application in receptor-targeted therapy. In the present work, the potential usefulness of the NaA nanozeolite as a carrier for radium radionuclides has been studied. 224Ra and 225Ra, α-particle emitting radionuclides, have been absorbed in the nanometer-sized NaA zeolite (30–70 nm) through simple ion exchange. 224,225Ra-nanozeolites exhibited very high stability in solutions containing physiological salt, EDTA, amino acids, and human serum. To make NaA nanozeolite particles dispersed in water their surface was modified with a silane coupling agent containing poly(ethylene glycol) molecules. This functionalization approach let us covalently attach a biomolecule to the NaA nanozeolite surface.
doi:10.1007/s11051-013-2082-7
PMCID: PMC3840288  PMID: 24307862
Radiotherapy; Nanomedicine; Nanozeolite; Radium radionuclides; Drug delivery
15.  Stability of silver nanoparticle monolayers determined by in situ streaming potential measurements 
Abstract
A silver particle suspension obtained by a chemical reduction was used in this work. Monolayers of these particles (average size 28 nm) on mica modified by poly(allylamine hydrochloride) were produced under diffusion-controlled transport. Monolayer coverages, quantitatively determined by atomic force microscopy (AFM) and SEM, was regulated by adjusting the nanoparticle deposition time and the suspension concentration. The zeta potential of the monolayers was determined by streaming potential measurements carried out under in situ (wet) conditions. These measurements performed for various ionic strengths and pH were interpreted in terms of the three-dimensional (3D) electrokinetic model. The stability of silver monolayers was also investigated using streaming potential and the AFM methods. The decrease in the surface coverage of particles as a function of time and ionic strength varied between 10−1 and 10−4 M was investigated. This allowed one to determine the equilibrium adsorption constant Ka and the binding energy of silver particles (energy minima depth). Energy minima depth were calculated that varied between −18 kT for I = 10−1 M and −19 kT for I = 10−4 for pH 5.5 and T = 298 K. Our investigations suggest that the interactions between surface and nanoparticles are controlled by the electrostatic interactions among ion pairs. It was also shown that the in situ electrokinetic measurements are in accordance with those obtained by more tedious ex situ AFM measurements. This confirmed the utility of the streaming potential method for direct kinetic studies of nanoparticle deposition/release processes.
Graphical Abstract
doi:10.1007/s11051-013-2076-5
PMCID: PMC3840291  PMID: 24307861
Deposition of silver particles; Release kinetics of silver nanoparticles; Monolayers of silver particles; Streaming potential of silver particle monolayers
16.  Core/shell-type nanorods of Tb3+-doped LaPO4, modified with amine groups, revealing reduced cytotoxicity 
Abstract
A simple co-precipitation reaction between Ln3+ cations (Ln = lanthanide) and phosphate ions in the presence of polyethylene glycol (PEG), including post-treatment under hydrothermal conditions, leads to the formation of Tb3+-doped LaPO4 crystalline nanorods. The nanoparticles obtained can be successfully coated with amorphous and porous silica, forming core/shell-type nanorods. Both products reveal intensive green luminescence under UV lamp irradiation. The surface of the core/shell-type product can also be modified with –NH2 groups via silylation procedure, using 3-aminopropyltriethoxysilane as a modifier. Powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy confirm the desired structure and needle-like shape of the products synthesized. Fourier transform infrared spectroscopy and specific surface area measurements by Brunauer–Emmett–Teller method reveal a successful surface modification with amine groups of the core/shell-type nanoparticles prepared. The nanomaterials synthesized exhibit green luminescence characteristic of Tb3+ ions, as solid powders and aqueous colloids, examined by spectrofluorometry. The in vitro cytotoxicity studies reveal different degree toxicity of the products. LaPO4:Tb3+@SiO2@NH2 exhibits the smallest toxicity against B16F0 mouse melanoma cancer cells and human skin microvascular endothelial cell lines, in contrast to the most toxic LaPO4:Tb3+@SiO2.
Graphical Abstract
doi:10.1007/s11051-013-2068-5
PMCID: PMC3840287  PMID: 24307860
Core/shell nanorods; Cytotoxicity; Surface modification; Amine groups –NH2; Luminescence; Tb3+-doped phosphates
17.  A highly efficient nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid groups as a solid acid catalyst for synthesis of 1,8-dioxo-octahydroxanthene derivatives 
Abstract
The functionalization of silica-coated Fe3O4 magnetic nanoparticles (Fe3O4@SiO2) using chlorosulfonic acid were afforded sulfonic acid-functionalized magnetic Fe3O4 nanoparticles (Fe3O4@SiO2–SO3H) that can be applied as an organic–inorganic hybrid heterogeneous catalyst. The used Fe3O4 magnetic nanoparticles are 18–30 nm sized that was rapidly functionalized and can be used as catalyst in organic synthesis. The prepared nanoparticles were characterized by X-ray diffraction analysis, magnetization curve, scanning electron microscope, dynamic laser scattering, and FT-IR measurements. The resulting immobilized catalysts have been successfully used in the synthesis of 1,8‐dioxo-octahydroxanthene derivatives under solvent free condition. This procedure has many advantages such as; a much milder method, a shorter reaction time, a wide range of functional group tolerance, and absence of any tedious workup or purification. Other remarkable features include the catalyst can be reused at least five times without any obvious change in its catalytic activity. This procedure also avoids hazardous reagents/solvents, and thus can be an eco-friendly alternative to the existing methods.
Graphical Abstract
A highly efficient nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid groups as a solid acid catalyst for synthesis of 1,8-dioxo-octahydroxanthene derivatives
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-013-2026-2) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-013-2026-2
PMCID: PMC3840292  PMID: 24307859
Magnetic nanoparticle; Silica; 1,8‐Dioxo-octahydroxanthene; Dimedone; Aromatic aldehydes; Nanostructured catalyst
18.  Evaluation of Airborne Particle Emissions from Commercial Products Containing Carbon Nanotubes 
The emission of the airborne particles from epoxy resin test sticks with different CNT loadings and two commercial products were characterized while sanding with three grit sizes and three disc sander speeds. The total number concentrations, respirable mass concentrations, and particle size number/mass distributions of the emitted particles were measured using a condensation particle counter, an optical particle counter, and a scanning mobility particle sizer. The emitted particles were sampled on a polycarbonate filter and analyzed using electron microscopy. The highest number concentrations (arithmetic mean = 4670 particles/cm3) were produced with coarse sandpaper, 2% (by weight) CNT test sticks and medium disc sander speed, whereas the lowest number concentrations (arithmetic mean = 92 particles/cm3) were produced with medium sandpaper, 2% CNT test sticks and slow disc sander speed. Respirable mass concentrations were highest (arithmetic mean = 1.01 mg/m3) for fine sandpaper, 2% CNT test sticks and medium disc sander speed and lowest (arithmetic mean = 0.20 mg/m3) for medium sandpaper, 0% CNT test sticks and medium disc sander speed. For CNT-epoxy samples, airborne particles were primarily micrometer-sized epoxy cores with CNT protrusions. No free CNTs were observed in airborne samples, except for tests conducted with 4% CNT epoxy. The number concentration, mass concentration, and size distribution of airborne particles generated when products containing CNTs are sanded depends on the conditions of sanding and the characteristics of the material being sanded.
doi:10.1007/s11051-012-1231-8
PMCID: PMC3507461  PMID: 23204914
Airborne particles; Carbon nanotubes; Number concentration; Particle size distribution; Respirable mass concentration; Sanding
19.  Synthesis and microwave absorption properties of electromagnetic functionalized Fe3O4–polyaniline hollow sphere nanocomposites produced by electrostatic self-assembly 
Highly regulated Fe3O4–polyelectrolyte-modified polyaniline (Fe3O4–PE@PANI) hollow sphere nanocomposites were successfully synthesized using an electrostatic self-assembly approach. The morphology and structure of the Fe3O4–PE@PANI nanocomposites were characterized using field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The results showed that the as-prepared nanocomposites had well-defined sizes and shapes, and the average size is about 500 nm. The assembly process was investigated. Magnetization measurements showed that the saturation magnetization of the nanocomposites was 38.6 emu g−1. It was also found that the Fe3O4–PE@PANI nanocomposites exhibited excellent reflection loss abilities and wide response bandwidths compared with those of PANI hollow spheres in the range 0.5–15 GHz. The Fe3O4–PE@PANI nanocomposites are, therefore, promising for microwave absorption applications.
doi:10.1007/s11051-013-1988-4
PMCID: PMC3825523  PMID: 24273439
Fe3O4 nanoparticles; Polyaniline hollow sphere; Nanocomposite; Polyelectrolyte; Microwave absorption
20.  Structural, spectroscopic and cytotoxicity studies of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals 
Abstract
Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. Their complex structure was formed spontaneously during the synthesis. The surface of these core/shell nanocrystals was additionally modified by silica. The properties of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals, formed in this way, were investigated. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO2 shell. X-ray diffraction patterns confirmed the trigonal crystal structure of TbF3@CeF3 nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. Crystallized as small discs, ‘the products’, with an average diameter around 10 nm, showed an increase in the concentration of Tb3+ ions from surface to the core of nanocrystals. In addition to photo-physical analyses, cytotoxicity studies were performed on HSkMEC (Human Skin Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The cytotoxicity of the nanomaterials was neutral for the investigated cells with no toxic or antiproliferative effect in the cell cultures, either for normal or for cancer cells. This fact makes the obtained nanocrystals good candidates for biological applications and further modifications of the SiO2 shell.
Graphical Abstract
.
doi:10.1007/s11051-013-1958-x
PMCID: PMC3825480  PMID: 24273438
Nanoparticles; Core/shell; Silica; Luminescence; Rare earth fluorides; Cytotoxicity
21.  Effects of serum on cytotoxicity of nano- and micro-sized ZnO particles 
Although an increasing number of in vitro studies are being published regarding the cytotoxicity of nanomaterials, the components of the media for toxicity assays have often varied according to the needs of the scientists. Our aim for this study was to evaluate the influence of serum—in this case, fetal bovine serum—in a cell culture medium on the toxicity of nano-sized (50–70 nm) and micro-sized (<1 μm) ZnO on human lung epithelial cells (A549). The nano- and micro-sized ZnO both exhibited their highest toxicity when exposed to serum-free media, in contrast to exposure in media containing 5 or 10 % serum. This mainly comes not only from the fact that ZnO particles in the serum-free media have a higher dosage-per-cell ratio, which results from large aggregates of particles, rapid sedimentation, absence of protein protection, and lower cell growth rate, but also that extracellular Zn2+ release contributes to cytotoxicity. Although more extracellular Zn2+ release was observed in serum-containing media, it did not contribute to nano-ZnO cytotoxicity. Furthermore, non-dissolved particles underwent size-dependent particle agglomeration, resulting in size-dependent toxicity in both serum-containing and serum-free media. A low correlation between cytotoxicity and inflammation endpoints in the serum-free medium suggested that some signaling pathways were changed or induced. Since cell growth, transcription behavior for protein production, and physicochemical properties of ZnO particles all were altered in serum-free media, we recommend the use of a serum-containing medium when evaluating the cytotoxicity of NPs.
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-013-1829-5) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-013-1829-5
PMCID: PMC3782657  PMID: 24078789
Nanoparticles; Cytotoxicity; A549; Zinc oxide; Serum
22.  Chitosan-capped gold nanoparticles for selective and colorimetric sensing of heparin 
In this contribution, novel chitosan-stabilized gold nanoparticles (AuNPs) were prepared by mixing chitosan with citrate-reductive AuNPs under appropriate conditions. The as-prepared chitosan-stabilized AuNPs were positively charged and highly stably dispersed in aqueous solution. They exhibited weak resonance light scattering (RLS) intensity and a wine red color. In addition, the chitosan-stabilized AuNPs were successfully utilized as novel sensitive probes for the detection of heparin for the first time. It was found that the addition of heparin induced a strong increase of RLS intensity for AuNPs and the color change from red to blue. The increase in RLS intensity and the color change of chitosan-stabilized AuNPs caused by heparin allowed the sensitive detection of heparin in the range of 0.2–60 μM (~6.7 U/mL). The detection limit for heparin is 0.8 μM at a signal-to-noise ratio of 3. The present sensor for heparin detection possessed a low detection limit and wide linear range. Additionally, the proposed method was also applied to the detection of heparin in biological media with satisfactory results.
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-013-1930-9) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-013-1930-9
PMCID: PMC3782634  PMID: 24078791
Gold nanoparticles; Resonance light scattering; Chitosan; Heparin; Colorimetric detection
23.  Magnetic properties of ferritin and akaganeite nanoparticles in aqueous suspension 
We have studied the magnetically induced optical birefringence Δn of horse spleen ferritin (HSF) and aqueous suspensions of several different-sized iron oxyhydroxide nanoparticles coated with different polysaccharides mimicking ferritin. The structure and dimensions of the akaganeite mineral core were characterized by XRD and TEM, respectively. The stability of the suspensions in the measurement temperature range from 278 to 358 K was confirmed by UV–Vis absorption spectroscopy. The values of optical polarizability anisotropy Δα, magnetic susceptibility anisotropy Δχ, and permanent magnetic dipole moment μm of the akaganeite nanoparticles have been estimated on the basis of the temperature dependence of the Cotton–Mouton (C–M) constant. The magnetic birefringence of Fe-sucrose has been described tentatively by different types of Langevin function allowing another estimation of Δχ and μm. The obtained permanent magnetic dipole moment μm of the studied akaganeite nanoparticles proves small and comparable to that of HSF. The value of μm is found to increase with decreasing nanoparticle diameter. Observed in a range spanning more than five orders of magnitude, the linear relation between the C–M constant and the iron concentration provides a basis for possible analytical application of the C–M effect in biomedicine. The established relation between the C–M constant and the nanoparticle diameter confirms that the dominant contribution to the measured magnetic birefringence comes from the magnetic susceptibility anisotropy Δχ. A comparison of the C–M constants of the studied akaganeite nanoparticles with the data obtained for HSF provides evidence that the ferritin core behaves as a non-Euclidian solid.
doi:10.1007/s11051-013-1902-0
PMCID: PMC3920033  PMID: 24532980
Magnetic birefringence; Cotton–Mouton effect; Akaganeite; Ferritin; Magnetic susceptibility anisotropy; Langevin function
24.  Water molecular flow control with a (5,5) nanocoil switch 
Molecular dynamics simulation was employed to investigate the diffusion behaviors of water molecules within a (5,5) carbon nanocoil (CNC) at different tensile strains, the length and coil diameter of CNC are 22 and 6.83 Ǻ, respectively. Condensed-phase, optimized molecular potentials for atomistic simulation studies were employed to model the interaction between atoms. The results show that the diffusion in the axial direction can be enhanced by the tensile strain and the water molecule flow can be blocked at a higher strain once the deformed areas appear at the higher strain. Moreover, the deformed (5,5) CNC at strain of 2.8 can recover its original structure at strain of 0, indicating that the adjustment of diffusion coefficient is repeatable by applying different strains in the axial direction.
doi:10.1007/s11051-013-1889-6
PMCID: PMC3782641  PMID: 24078790
Nanocoil; Molecular dynamics; Water molecule; Diffusion coefficient
25.  Solid-state MAS NMR, TEM, and TGA studies of structural hydroxyl groups and water in nanocrystalline apatites prepared by dry milling 
A series of nanocrystalline calcium hydroxyapatites was prepared by dry milling and characterized using proton and 31P MAS NMR, TEM, and TGA methods. The samples contained stubby rod-shaped crystals, which length and width varied in the 130–30 and 95–20 nm ranges, respectively. It was confirmed that concentration of structural hydroxyl groups in nanocrystalline apatites decreases with the decreasing crystal size. In the series of the studied apatites, the decrease was from 86 to ca. 50 % in reference to stoichiometric apatite. Water was found in the surface hydrated layer and in the c-axis channels, in which compartments existed as adsorbed and structural, respectively. Molecules of the adsorbed water were capable of moving from the crystal surface into the lattice c-axis channels of apatite. This process introduced considerable structural disorder within and around those channels and reduced the content of the structural hydroxyl groups, particularly in the region underneath the apatite crystal surface.
Electronic supplementary material
The online version of this article (doi:10.1007/s11051-013-1868-y) contains supplementary material, which is available to authorized users.
doi:10.1007/s11051-013-1868-y
PMCID: PMC3751289  PMID: 23990754
Apatite; Milling; Nanocrystals; Hydroxyl groups; Structural water; NMR

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