5 nm Silver Nanoparticles Amplify Clinical Features of Atopic Dermatitis in Mice by Activating Mast Cells.

The triggering effect of silver nanoparticles (NPs) on the induction of allergic reactions is evaluated, by studying the activation of mast cells and the clinical features of atopic dermatitis in a mouse model. Granule release is induced in RBL-2H3 mast cells by 5 nm, but not 100 nm silver NPs. Increases in the levels of reactive oxygen species (hydrogen peroxide and mitochondrial superoxide) and intracellular Ca++ in mast cells are induced by 5 nm silver NPs. In a mouse model of atopic dermatitis induced by a mite allergen, the skin lesions are more severe and appear earlier in mice treated simultaneously with 5 nm silver NPs and allergen compared with mice treated with allergen alone or 100 nm silver NPs and allergen. The histological findings reveal that number of tryptase-positive mast cells and total IgE levels in the serum increase in mice treated with 5 nm silver NPs and allergen. The results in this study indicate that cotreatment with 5 nm silver NPs stimulates mast cell degranulation and induces earlier and more severe clinical alterations in allergy-prone individuals.

Fabrication of highly luminescent and concentrated quantum dot/poly(methyl methacrylate) nanocomposites by matrix-free methods.

We present matrix-free methods for fabricating highly luminescent and transparent CdSe/ZnS quantum dot (QD)/polymer nanocomposites utilizing poly(methyl methacrylate) (PMMA)-grafted QDs with various molecular weights. We found that the QD-PMMA nanocomposites prepared by these matrix-free methods were superior to those prepared by a simple blending method in relation to their optical property, QD dispersion, and quantum efficiency (QE). In particular, a matrix-free nanocomposite containing PMMA with a molecular weight of 2000 had the highest QE (52.8%) and transmittance of all the samples studied even at a very high QD concentration (49 wt%). This finding was attributed to the enhanced passivation of the QD surface due to the higher grafting density of the PMMA ligands and reduced energy transfer due to more uniform dispersion of QDs. Finally, we applied the nanocomposites to LED devices, and found that the matrix-free nanocomposite exhibited a higher color conversion efficiency and smaller redshift in the peak emission wavelength than that prepared using a simple blending method.

Highly luminescent silica-coated CdS/CdSe/CdS nanoparticles with strong chemical robustness and excellent thermal stability.

We present facile synthesis of bright CdS/CdSe/CdS@SiO2 nanoparticles with 72% of quantum yields (QYs) retaining ca 80% of the original QYs. The main innovative point is the utilization of the highly luminescent CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) as silica coating seeds. The significance of inorganic semiconductor shell passivation and structure design of quantum dots (QDs) for obtaining bright QD@SiO2 is demonstrated by applying silica encapsulation via reverse microemulsion method to three kinds of QDs with different structure: CdSe core and 2 nm CdS shell (CdSe/CdS-thin); CdSe core and 6 nm CdS shell (CdSe/CdS-thick); and CdS core, CdSe intermediate shell and 5 nm CdS outer shell (CdS/CdSe/CdS-SQW). Silica encapsulation inevitably results in lower photoluminescence quantum yield (PL QY) than pristine QDs due to formation of surface defects. However, the retaining ratio of pristine QY is different in the three silica coated samples; for example, CdSe/CdS-thin/SiO2 shows the lowest retaining ratio (36%) while the retaining ratio of pristine PL QY in CdSe/CdS-thick/SiO2 and SQW/SiO2 is over 80% and SQW/SiO2 shows the highest resulting PL QY. Thick outermost CdS shell isolates the excitons from the defects at surface, making PL QY relatively insensitive to silica encapsulation. The bright SiO2-coated SQW sample shows robustness against harsh conditions, such as acid etching and thermal annealing. The high luminescence and long-term stability highlights the potential of using the SQW/SiO2 nanoparticles in bio-labeling or display applications.

Toxic and adjuvant effects of silica nanoparticles on ovalbumin-induced allergic airway inflammation in mice.

BACKGROUND: Silica nanoparticles (SNPs) can easily enter in respiratory system via inhalation because of their low molecular weight and ease of dispersion. Toxicity and adverse effects of SNPs vary according to the physical characteristics of the particle. METHODS: To evaluate the toxic and adjuvant effects of 3 types of SNPs in the airway system, six-week-old female BALB/c mice were intranasally administered 3 types of SNPs (spherical [S-SNP], mesoporous [M-SNP], and polyethylene glycol-conjugated [P-SNP]) alone or SNPs/ovalbumin (OVA), three times weekly for 2 weeks. Airway hyper-responsiveness (AHR), bronchoalveolar lavage fluid (BALF), cytokine levels, and histology of the lungs were analyzed. RESULTS: The S-SNPs/OVA group and M-SNPs/OVA group showed significant AHR, compared to the control group. Among all SNP-treated groups, the group administered SNPs/OVA showed greater inflammatory cell infiltration in BALF, extensive pathological changes, and higher cytokine levels (IL-5, IL-13, IL-1ß, and IFN-γ) than those administered SNPs alone or saline/OVA. CONCLUSION: Exposure to SNPs alone and SNPs/OVA induced toxicity in the respiratory system. SNPs alone showed significant toxic effects on the airway system. Meanwhile, SNPs/OVA exerted adjuvant effects to OVA of inducing allergic airway inflammation. In particular, M-SNPs showed the most severe airway inflammation in both direct toxicity and adjuvant effect assays. P-SNPs induced less inflammation than the other types of SNPs in both models.

Quantum efficiency of colloidal suspensions containing quantum dot/silica hybrid particles.

We have investigated the fluorescence properties of colloidal suspensions conntaining quantum dot (QD)/silica hybrid particles. First, we synthesized QD/silica hybrid particles with silica-QD-silica (SQS) core-shell-shell geometry, and monitored the quantum efficiencies of their suspensions at various particle concentrations. We found that the quantum efficiency (QE) of SQS particles in deionized (DI) water was much lower than that of the QDs even at low particle concentration, mainly due to the light scattering of emitted photons at the silica/water interface, followed by reabsorption by QDs. As the concentration of SQS particles was increased, both light scattering and reabsorption by QDs became more important, which further reduced the QE. Refractive index-matched solvent, however, reduced light scattering, yielding greater QE than DI water. Next, we induced aggregation of SQS particles, and found that QE increased as particles aggregated in DI water because of reduced light scattering and reabsorption, whereas it remained almost constant in the refractive index-matched solvent. Finally, we studied aggregation of highly concentrated silica particle suspensions containing a low concentration of SQS particles, and found that QE increased with aggregation because light scattering and reabsorption were reduced.

Gold nanoparticles-based colorimetric assay for cathepsin B activity and the efficiency of its inhibitors.

Cathepsin B has been suggested to be a prognostic marker of melanoma, glioma, and a variety of cancers such as brain, breast, colon, esophageal, gastric, lung, ovarian, and thyroid cancers. Cathepsin B inhibitors have also been considered as anticancer drug candidates; hence, there has been a growing need for a probe which enables the selective and simple detection of cathepsin B and its inhibitors. For the purpose of selective assay, a cathepsin B-specific substrate, N,N'-diBoc-dityrosine-glycine-phenylalanine-3-(methylthio)propylamine (DBDY-Gly-Phe-MTPA) was synthesized in this study. Phe-MTPA, which was produced via cathepsin B-catalyzed hydrolysis of DBDY-Gly-Phe-MTPA, allowed aggregation of gold nanoparticles (AuNPs) leading to a color change from red to blue. When tested for cathepsins B, L, and S, this assay method exhibited AuNPs color change only in reaction to cathepsin B. The limits of detection for cathepsin B was 10 and 5 nM in the 1 and 2 h hydrolysis reactions, respectively. The efficiency of cathepsin B inhibitors such as leupeptin, antipain, and chymostatin was easily compared by the degree of color change. Moreover, IC50 values of leupeptin, antipain, and chymostatin were found to be 0.11, 0.48, and 1.78 µM, respectively, which were similar to the results of previous studies. Therefore the colorimetric assay of cathepsin B and cathepsin B inhibitors using DBDY-Gly-Phe-MTPA and AuNPs allowed not only the selective but also the simple assay of cathepsin B and its inhibitors, which was possible with the naked eye.

Synthesis and characterization of ethosomal contrast agents containing iodine for computed tomography (CT) imaging applications.

As a first step in the development of novel liver-specific contrast agents using ethosomes for computed tomography (CT) imaging applications, we entrapped iodine within ethosomes, which are phospholipid vesicular carriers containing relatively high alcohol concentrations, synthesized using several types of alcohol, such as methanol, ethanol, and propanol. The iodine containing ethosomes that were prepared using methanol showed the smallest vesicle size (392 nm) and the highest CT density (1107 HU). The incorporation of cholesterol into the ethosomal contrast agents improved the stability of the ethosomes but made the vesicle size large. The ethosomal contrast agents were taken up well by macrophage cells and showed no cellular toxicity. The results demonstrated that ethosomes containing iodine, as prepared in this study, have potential as contrast agents for applications in CT imaging.

Raman detection of localized transferrin-coated gold nanoparticles inside a single cell.

We investigated the cellular uptake behavior of non-fluorescent metal nanoparticles (NPs) by use of surface-enhanced Raman scattering (SERS) combined with dark-field microscopy (DFM). The uptake of Au NPs inside a single cell could also be identified by DFM first and then confirmed by z-depth-dependent SERS at micrometer resolution. Guided by DFM for the location of Au NPs, an intracellular distribution assay was possible using Raman dyes with unique vibrational marker bands in order to identify the three-dimensional location inside the single cell by obtaining specific spectral features. Au NPs modified by 4-mercaptobenzoic acid (MBA) bearing its -COOH surface functional group were used to conjugate transferrin (Tf) protein using the 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) reaction. The protein conjugation reaction on Au surfaces was examined by means of color change, absorption spectroscopy, and SERS. Our results demonstrate that DFM techniques combined with SERS may have great potential for monitoring biological processes with protein conjugation at the single-cell level.

Hydrogen-Bonding-Mediated Molecular Vibrational Suppression for Enhancing the Fluorescence Quantum Yield Applicable for Visual Phenol Detection.

It is generally accepted that while efficient suppression of molecular vibration is inevitable for purely organic phosphors due to their long emission lifetime in the regime of 1 ms or longer, fluorophores having a lifetime in the nanoseconds regime are not sensitive to collisional quenching. Here, however, we demonstrate that a fluorophore, 2,5-bis(hexyloxy)terephthaldehyde (BHTA), capable of having hydrogen bonding (H bonding) via its two aldehyde groups can have a largely enhanced (450%) fluorescence quantum yield (QY) in amorphous poly(acrylic acid) (PAA) matrix compared to its crystalline powder. We ascribe this enhanced QY to the efficient suppression of molecular vibrations via intermolecular H bonding. We confirm this feasibility by conducting temperature-dependent fluorescence emission intensity measurement. As gaseous phenol can intervene with the H bonding between BHTA and PAA, interestingly, BHTA embedded in PAA can selectively detect gaseous phenol by a sharp fluorescence emission intensity drop that is visibly recognizable by the naked eye. The results provide an insightful molecular design strategy for a fluorophore and fluorometric sensory system design for enhanced photoluminescence QY and convenient detection of various volatile organic compounds.

Surface-enhanced plasmon resonance detection of nanoparticle-conjugated DNA hybridization.

We have investigated surface-enhanced plasmon resonance detection of DNA hybridization. Surface enhancement was based on the excitation of localized surface plasmon using subwavelength nanogratings, at a 300 nm period, coated with 24-mer ssDNA oligonucleotide, while optical signatures of DNA were amplified at the same time by gold nanoparticles conjugated with complementary ssDNA strands. When using nanoparticles of different sizes, maximum sensitivity enhancement, of more than 18 times, was obtained with nanoparticles of 20 nm diameter. This enhancement is mainly due to nanoparticle-associated signal amplification. Additional surface enhancement boosted the detection sensitivity by 57%. We have also confirmed the sensitivity enhancement to be linearly related to nanoparticle volume.

Kinetics of gold nanoparticle aggregation: experiments and modeling.

We investigate the aggregation kinetics of gold nanoparticles using both experimental techniques (i.e., quasi-elastic light scattering, UV-visible spectroscopy, and transmission electron microscopy) and mathematical modeling (i.e., constant-number Monte Carlo). Aggregation of gold nanoparticles is induced by replacing the surface citrate groups with benzyl mercaptan. We show that the experimental results can be well described by the model in which interparticle interactions are described by the classical DLVO theory. We find that final gold nanoparticle aggregates have a fractal structure with a mass fractal dimension of 2.1-2.2. Aggregation of approximately 11 initial gold nanoparticles appears to be responsible for the initial color change of suspension. This kinetic study can be used to predict the time required for the initial color change of a gold nanoparticle suspension and should provide insights into the design and optimization of colorimetric sensors that utilize aggregation of gold nanoparticles.

Wafer-level detection of organic contamination by ZnO-rGO hybrid-assisted laser desorption/ionization time-of-flight mass spectrometry.

A technique for wafer-level detection of organic contaminations via surface-assisted laser desorption/ionization time-of-flight mass spectrometry was developed. To replace the organic matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, zinc oxide-reduced graphene oxide (ZnO-rGO) hybrid was prepared by a hydrothermal reaction and used as the matrix in the detection of benzo[a]pyrene (B[a]P). By varying the rGO content and the amount of hybrid, the optimal rGO content in the hybrid for the detection of B[a]P was determined to be 4 wt% and the optimal amount of hybrid was 20 ng. The limit of detection of this method was found to be 1.6 × 1014 C atoms cm-2, which is lower than the concentration of residual organic contamination at which serious failure occurs during semiconductor fabrication. This method was also successfully used to detect other aromatic and aliphatic species on a semiconductor wafer. This approach is fast, accurate, simple, and inexpensive compared to other conventional methods, and can be used to identify localized micro-contamination in the semiconductor industry.

Microscopic analysis of ester hydrolysis reaction catalyzed by Candida rugosa lipase.

The relationship between the kinetics of the lipase-catalyzed oil hydrolysis and the surface area distribution of oil droplets was investigated using ethyl decanoate and gum Arabic (GA) as a model oil and an emulsifier, respectively. Along an ethyl decanoate concentration gradient between 2 and 8 mM, the initial hydrolysis rate increased at 0.25% (w/v) GA but did not change at 1.0% (w/v) GA. At 0.25% GA, the surface area of droplets was narrowly distributed regardless of the ethyl decanoate concentration. However, at 1.0% GA and with ethyl decanoate concentrations higher than 2 mM, the fraction of relatively large droplets with a surface area larger than approximately 200 microm2, suddenly increased. The microscopy of ethyl decanoate emulsion during the hydrolysis reaction indicates that the large oil droplets were not hydrolyzed. At 20 mM ethyl decanoate where the hydrolysis rate remained the same between 0.25% and 1.0% GA, the surface area of droplets was narrowly distributed at 0.25% and 1.0% GA. Therefore, the constant hydrolysis rate observed in the emulsion of ethyl decanoate between 2 and 8 mM containing GA at 1.0%, is believed to be caused by the relatively large oil droplets with the interface quality differing from that of the small oil droplets.

Kinetics and thermodynamics of bromophenol blue adsorption by a mesoporous hybrid gel derived from tetraethoxysilane and bis(trimethoxysilyl)hexane.

A mesoporous hybrid gel is prepared with tetraethoxysilane (TEOS) and bis(trimethoxysilyl)hexane (TSH) as precursors without using any templating agent. Nitrogen sorption, TG-DTA, FTIR, and point of zero charge (PZC) measurement are used to characterize the gel. The gel has a specific surface area of 695 m(2) g(-1) with a pore size of 3.5 nm, a pore volume of 0.564 cm(3) g(-1), and a point of zero charge (PZC) of 6.2. The kinetics and thermodynamics of bromophenol blue (BPB) adsorption by the gel in aqueous solution are investigated comprehensively. The effects of initial BPB concentration, pH, ionic strength, and temperature on the adsorption are investigated. Kinetic studies show that the kinetic data are well described by the pseudo-second-order kinetic model. Initial adsorption rate increases with the increase in initial BPB concentration and temperature. Adsorption activation energy is found to be 62.5-67.5 kJ mol(-1) depending on the initial BPB concentration. Internal diffusion appears to be the rate-limiting step for the adsorption process. The equilibrium adsorption amount increases with the increase in the initial BPB concentration, solution acidity, and ionic strength, but decreases with the increase in temperature. The thermodynamic analysis indicates that the adsorption is spontaneous and exothermic. The adsorption isotherms can be well described with Freundlich equation indicating the heterogeneity of the hybrid gel surface. Electrostatic and hydrophobic interactions are suggested to be the dominant mechanism for adsorption.

Surface properties of submicrometer silica spheres modified with aminopropyltriethoxysilane and phenyltriethoxysilane.

The surface of submicrometer silica spheres are modified with aminopropyl and phenyl groups through a one-step process. Various experimental techniques, i.e., scanning electron microscopy (SEM), quasi-elastic light scattering (QELS), differential scanning calorimetry (DSC), thermogravimetry (TG), zeta potential measurement, nitrogen sorption, and water vapor and organic dye adsorption are used to comprehensively characterize the pure (TEOS particles) and modified silica particles. The SEM micrographs of the particles demonstrate that the modified particles are spherical with uniform size and shape. The particles modified with aminopropyl groups (APTES particles) show the highest isoelectric point (IEP) and the highest weight loss at 780 degrees C because of the basic nature of aminopropyl groups and the higher reactivity of aminopropyltriethoxysilane. The particles modified with the phenyl groups (PhTES particles) show the lowest water vapor adsorption because their surface is more hydrophobic than that of TEOS and APTES particles. The organic dye (brilliant blue FCF or BBF) adsorption experiments demonstrate that the adsorption capacity of the particles increases greatly after acidification. This is caused by the protonation of silanol groups and amine groups on the particle surface, which presents an enhanced electrostatic attraction with BBF anions. The APTES particles exhibit the highest dye adsorption due to the hydrophobic attractions and the enhanced electrostatic attractions from aminopropyl groups.

Controlled release of lidocaine hydrochloride from the surfactant-doped hybrid xerogels.

We investigate the controlled release of lidocaine hydrochloride from the doped silica-based xerogels. In the xerogel preparation, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), and propyltriethoxysilane (PTES) are used as precursors, and a nonionic surfactant Igepal CO 720 is used as a dopant. The experimental results suggest that the release of lidocaine hydrochloride can be easily controlled by partially substituting TEOS with the organosilanes, and/or by adding the dopant. Adding the organosilane precursors lowers the release of both the drug and the surfactant in the order of TEOS, MTES/TEOS, and PTES/TEOS xerogels. The release from the PTES/TEOS xerogels is much lower than that from the other xerogels. The release of lidocaine hydrochloride is obviously suppressed by the addition of Igepal CO 720, while the release of Igepal CO 720 is slightly promoted by the addition of the drug. The overall release process is found to be diffusion-controlled, and the release behaviors can be well explained by considering the effects of the textual properties of the xerogels and the interactions among the drug, the surfactant, and the xerogel matrices.

Acute exposure to silica nanoparticles aggravate airway inflammation: different effects according to surface characteristics.

Silica nanoparticles (SNPs) are widely used in many scientific and industrial fields despite the lack of proper evaluation of their potential toxicity. This study examined the effects of acute exposure to SNPs, either alone or in conjunction with ovalbumin (OVA), by studying the respiratory systems in exposed mouse models. Three types of SNPs were used: spherical SNPs (S-SNPs), mesoporous SNPs (M-SNPs), and PEGylated SNPs (P-SNPs). In the acute SNP exposure model performed, 6-week-old BALB/c female mice were intranasally inoculated with SNPs for 3 consecutive days. In the OVA/SNPs asthma model, the mice were sensitized two times via the peritoneal route with OVA. Additionally, the mice endured OVA with or without SNP challenges intranasally. Acute SNP exposure induced significant airway inflammation and airway hyper-responsiveness, particularly in the S-SNP group. In OVA/SNPs asthma models, OVA with SNP-treated group showed significant airway inflammation, more than those treated with only OVA and without SNPs. In these models, the P-SNP group induced lower levels of inflammation on airways than both the S-SNP or M-SNP groups. Interleukin (IL)-5, IL-13, IL-1ß and interferon-γ levels correlated with airway inflammation in the tested models, without statistical significance. In the mouse models studied, increased airway inflammation was associated with acute SNPs exposure, whether exposed solely to SNPs or SNPs in conjunction with OVA. P-SNPs appear to be relatively safer for clinical use than S-SNPs and M-SNPs, as determined by lower observed toxicity and airway system inflammation.

Effect of additional carbon source on naphthalene biodegradation by Pseudomonas putida G7.

Addition of a carbon source as a nutrient into soil is believed to enhance in situ bioremediation by stimulating the growth of microorganisms that are indigenous to the subsurface and are capable of degrading contaminants. However, it may inhibit the biodegradation of organic contaminants and result in diauxic growth. The objective of this work is to study the effect of pyruvate as another carbon source on the biodegradation of polynuclear aromatic hydrocarbons (PAHs). In this study, naphthalene was used as a model PAH, ammonium sulfate as a nitrogen source, and oxygen as an electron acceptor. Pseudomonas putida G7 was used as a model naphthalene-degrading microorganism. From a chemostat culture, the growth kinetics of P. putida G7 on pyruvate was determined. At concentrations of naphthalene and pyruvate giving similar growth rates of P. putida G7, diauxic growth of P. putida G7 was not observed. It is suggested that pyruvate does not inhibit naphthalene biodegradation and can be used as an additional carbon source to stimulate the growth of P. putida G7 that can degrade polynuclear aromatic hydrocarbons.

Distribution of phenanthrene between soil and an aqueous phase in the presence of anionic micelle-like amphiphilic polyurethane particles.

Sorption of micelle-like amphiphilic polyurethane (APU) particles to soil was studied and compared to that of a model anionic surfactant, sodium dodecyl sulfate (SDS). Three types of APU particles with different hydrophobicity were synthesized from urethane acrylate anionomers (UAA) and used in this study. Due to the chemically cross-linked structure, APU exhibited less sorption to the soil than SDS and a greater reduction in the sorption of phenanthrene, a model soil contaminant, to the soil was observed in the presence of APU than SDS even though the solubility of phenanthrene was higher in the presence of SDS than APU. A mathematical model was developed to describe the phenanthrene distribution between soil and an aqueous phase containing APU particles. The sorption of phenanthrene to the test soil could be well described by Linear isotherm. APU sorption to the soil was successfully described by Langmuir and Freundlich isotherms. The partition of phenanthrene between water and APU were successfully explained with a single partition coefficient. The model, which accounts for the limited solubilization of phenanthrene in sorbed APU particles, successfully described the experimental data for the distribution of phenanthrene between the soil and the aqueous phase in the presence of APU.