Search

The specific properties of silver nanoparticles (AgNPs), such as antimicrobial activity and electrical conductivity, allow them to be used in many fields. However, their expanding application is also raising health, environmental and safety concerns. Previous in vivo AgNP toxicity studies have indicated a gender-different accumulation of silver in the kidneys, with 2-3 times more silver in female kidneys compared to male kidneys. However, no other studies have further addressed this gender difference. Accordingly, the current study investigated the gender-dependent effect of AgNPs on the kidney gene level based on toxicogenomic studies of kidneys obtained from rats exposed to AgNPs via inhalation for 12 weeks. When compared with the fresh air control, the silver nanoparticle-exposed kidneys included 104 genes with a more than 1.3-fold expression increase. For the male rat kidneys exposed to a low or high dose of silver nanoparticles, 96 genes exhibited expression changes, where six genes changed with both the low and high dose; four increased and two decreased. Meanwhile, for the female rat kidneys exposed to a low or high dose of silver nanoparticles, 66 genes exhibited expression changes, where 11 genes changed with both the low and high dose; nine increased and two decreased. Gender-dependent gene expression changes of more than 2-fold were linked to 163 genes, with 79 genes in the male kidneys and 84 genes in the female kidneys, plus gender-dependent gene expression changes of more than 5-fold were linked to 21 genes. However, no genes involved in apoptosis or the cell cycle were activated by the 12-week silver nanoparticle inhalation exposure. Overall, the male rat kidneys showed a higher expression of genes involved in xenobiotic metabolism, while the female rat kidneys showed a higher expression of genes involved in extracellular signaling.

Although the safety of gold nanoparticle (AuNP) use is of growing concern, most toxicity studies of AuNPs had focused on their chemical characteristics, including their physical dimensions, surface chemistry, and shape. The present study examined the susceptibility of rodents with healthy or damaged livers to AuNP-induced hepatotoxicity. To induce a model of liver injury, mice were fed a methionine- and choline-deficient (MCD) diet for 4 weeks. Sizes and biodistribution of 15-nm PEGylated AuNPs were analyzed by transmission electron microscopy. Levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were estimated with an automatic chemical analyzer, and liver sections were subjected to pathological examination. Activities of antioxidant enzymes were determined by biochemical assay. Lateral tail vein injection of MCD diet-fed mice with 5 mg kg−1 AuNPs significantly elevated the serum ALT and AST levels compared to MCD diet-fed mice injected with mPEG (methylpolyethylene glycol). Similarly, severe hepatic cell damage, acute inflammation, and increased apoptosis and reactive oxygen species (ROS) production were observed in the livers of AuNP-injected mice on the MCD diet; these liver injuries were attenuated in mice fed a normal chow diet. The results suggest that AuNPs display toxicity in a stressed liver environment by stimulating the inflammatory response and accelerating stress-induced apoptosis. These conclusions may point to the importance of considering health conditions, including liver damage, in medical applications of AuNPs.

We investigate the cellular uptake behaviors and efficacy of folate-coated gold nanoparticles (AuNPs) for the targeted drug delivery system in human cancer cells. Folate-conjugated AuNPs embedded with a purine analogue cancer drug of 6-mercaptopurine (6MP) were assembled via a 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) coupling reaction between the amino group of 4-aminobenzenethiol (ABT) and the carboxyl group of folic acid. The assembly of folate and 6MP on AuNPs has been examined by absorption spectroscopy, transmission electron microscopy (TEM), and confocal Raman spectroscopy. The internalization of the conjugated AuNPs inside the folate receptor-positive HeLa and KB cells was checked by TEM and dark-field microscopy (DFM) combined with label-free confocal spectroscopy over the depth variable z at a micrometer resolution. DFM live cell imaging of folate-conjugated AuNPs in HeLa cells indicated that the targeted AuNPs appeared to attach on the cell surfaces and enter into the cell with an hour. The cell viability was also compared to estimate the efficacy of folate-conjugated AuNP delivery systems. Folate receptor-targeted AuNP systems appeared to decrease cancer cell viability both in vitro and in vivo more than did the use of the 6MP-coated AuNPs drug without any targeting systems. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.

Intracellular uptake of serum-coated gold nanoparticles (AuNPs) in a single mammalian cell was examined in order to investigate the interactions of cell culture media and aromatic thiol-functionalized gold surfaces using micro-spectroscopic tools. The AuNPs modified by the aromatic thiols of para-aminobenzenethiol (ABT), para-hydroxy benzenethiol (HBT), and para-carboxylic benzenethiol (CBT, para-mercaptobenzoic acid) bearing NH(2), OH, and COOH surface functional groups are presumed to adsorb the serum proteins as indicated from the compiled quartz crystal microbalance (QCM) data. The QCM results indicate that among the constituents, fetal bovine serum (FBS) should be the major adsorbate species on AuNPs incubated in Roswell Park Memorial Institute (RPMI) medium. The functionalized AuNPs were found to be internalized as an aggregation state in mammalian cells as evidenced by transmission electron microscopy (TEM) images. We monitored such cellular uptake behaviors of aromatic thiol-modified AuNPs using dark-field microscopy (DFM)-guided confocal surface-enhanced Raman scattering techniques in order to identify the three-dimensional localization inside the single cell. We found that the uptake amounts of ABT, HBT, and CBT were similar by counting up to 70 particles inside the cells incubated in the solution mixture of the aromatic thiol and 1,4-phenylenediisocyanide (PDIC) as a reference. This result indicates for the short aromatic thiol compounds, the AuNPs should enter the cell after the serum-coating regardless of the surface functional groups. Considering that the aromatic thiols have little effect on the serum coating, the DFM/SERS method is an effective tool for monitoring the localization of AuNPs inside a single cell.

The first evaluation of the β for 2-[2-(p-diethylaminophenyl)vinyl]furan derivatives is reported in comparison with the corresponding thiophene derivative.

Strahlemanner: Fulleren-Siliciumdioxid-Hybridnanopartikel verfugen uber helle Photolumineszenz, hohe Photobestandigkeit und geringe Zelltoxizitat – alles Vorteile bei der Verwendung als Bildgebungsagentien fur biologische Proben. Die Photolumineszenz der Nanopartikel beruht auf den C-O-Si-Bindungen (siehe Bild).

Blinking of zinc-blende CdSe/ZnS core/shell nanocrystals are studied as a function of surface passivating ligands. Organic-soluble CdSe/ZnS core/shell nanocrystals are prepared by colloidal synthesis free of trioctylphosphine oxide and converted into water-soluble ones by ligand exchange with three different hydrophilic thiols, 2-aminoethanethiol, 3-mercapto-1-propanol, and 3-mercaptopropionic acid. The zinc-blende lattice structure is confirmed by powder X-ray diffraction, the size and shape distributions are visualized by high-resolution transmission electron microscopy, and hydrodynamic size distributions of water-soluble nanocrystals are determined by dynamic light scattering. Ligand-dependent optical properties, such as the absorption and emission spectra as well as the photoluminescence lifetime, are obtained in both solution and glass substrate to characterize the effects of ligand on the bright state of nanocrystals. The time trace of blinking is recorded for single nanocrystals in polymer film. Both on- and off-time distributions are fit to a power law. The off-time exponents are clustered at 1.67 ± 0.05, whereas the on-time exponents are scattered in the range of 1.71–2.25. The thiolate conjugation on the surface zinc atom greatly reduces the on-time duration, suggesting that the rate of photoinduced charge separation from the bright (on) to the dark (off) state increases as the number of surface hole-trap states increases.

We propose a new scheme of matrix-free laser desorption/ionization with cation assistance for surface mass spectrometry of self-assembled monolayers (SAMs) of alkanethiolates on gold substrates and gold nanoparticles (NPs). In a proof-of-concept experiment, a simple treatment using an aqueous salt solution such as NaI(aq) was shown to lead to a significant laser desorption/ionization, producing the characteristic (disulfide) ions of alkanethiolate molecules from the monolayers. Further efforts to understand the mechanism were also given, including laser power and salt concentration dependence studies. In the power dependence study, the characteristic ions were found to be produced at low laser power where no gold substrate species was seen. At high laser power, the generation of gold species, Au(+)-Au5(+), resulted in a saturation behavior in the characteristic mass peak for alkanethiolate molecules. In addition, characteristic ions with gold adducts were not observed at any laser power. With increasing salt concentration, the characteristic mass peak was gradually increased. The results suggest that the adduct formation of a cation with alkanethiolates in the monolayers provide a facile pathway to supply a charge to UV laser-desorbed secondary neutrals for mass spectrometric detection. This cation-assisted laser desorption/ionization (CALDI) mass spectrometry was further examined with the SAMs and mixed SAMs with various terminals such as -OH, -OCH3, -NH2, -ethylene (-CH=CH2), and -acetylene (-C[triple bond]CH). The CALDI method was also successfully applied to surface mass spectrometry of monolayer-protected gold NPs (approximately 16 nm diameter) with OH- and COOH-terminated SAMs. The unique advantages of the matrix-free CALDI method may extend our capability in investigations of interfacial chemistry at SAMs as well as mass spectrometric applications using biochips and nanoparticles.

Nanoparticles are of great interest due to their wide variety of biomedical and bioengineering applications. However, they affect cellular differentiation and/or intracellular signaling when applied and exposed to target organisms or cells. The brown adipocyte is a cell type important in energy homeostasis and thus closely related to obesity. In this study, we assessed the effects of silica nanoparticles (SNPs) on brown adipocyte differentiation. The results clearly showed that brown adipocyte differentiation was significantly repressed by exposure to SNPs. The brown adipocyte-specific genes as well as mitochondrial content were also markedly reduced. Additionally, SNPs led to suppressed p38 phosphorylation during brown adipocyte differentiation. These effects depend on the size of SNPs. Taken together, these results lead us to suggest that SNP has anti-brown adipogenic effect in a size-dependent manner via regulation of p38 phosphorylation.

The intramolecular photocyclization of aryl halide has been investigated in relation to the synthetic method and the reaction mechanism. It is reported that heterocyclic molecular systems are formed from the photocyclization of haloarene tethered to arene by several linkages and a photohomolytic radical mechanism is involved in the photocyclization of N-phenylalkyl-2-halopyridinium and N-(2-halophenyl)alkyl pyridinium salts. In conjunction with the study of the heterocyclic ring formation, we observed that photoreaction of N-(2-halophenyl)pyridinecarboxamide in a basic medium produced an intramolecular photosubstitution product, 2-pyridinylbenzoxazole, instead of a photocyclization product, whereas photoreaction of 2-chloro-N-pyridinylbenzamide in a weak basic or neutral medium afforded an intramolecular photocyclization product, benzo[c]naphthyridinones. These reactions are straightforward and valuable for the syntheses of heterocyclic compounds such as benzoxazole and benzonaphthyridinone derivatives. Thus, it is desirable to develop the synthetic methods of the heterocyclic compounds and to clarify their reaction mechanisms. In this work, we have studied the photochemical reaction mechanism of 2-halo-N-pyridinylbenzamide by using a nanosecond laser flash photolysis technique.

Many fundamental optical properties of InGaN have not yet been fully understood. Several researchers reported that the emission results mainly from recombination of excitons localized at certain potential minima originating from InGaN compositional fluctuations. In this work, we have employed photoluminescence (PL), photoreflectance (PR), and time-resolved photoluminescence (TRPL) measurements to study the mechanisms of optical transitions in InGaN-GaN double heterostructures.

The photochemical behavior of 2-halo-N-pyridinylbenzamide (1-4 in Chart 1) was studied. The photoreaction of 2-chloro-N-pyridinylbenzamides 1a, 2a, 3a, and 4 afforded photocyclized products, benzo[c]naphthyridinones (6-9 and 16), in high yield, whereas the bromo analogues 1b, 2b, and 3b produced extensively photoreduced products, N-pyridinylbenzamides (1c, 10, and 11), with minor photocyclized product. Since the photocyclization reaction of 2-chloro-N-pyridinylbenzamide is retarded by the presence of oxygen and sensitized by the presence of a triplet sensitizer, acetone or acetophenone, a triplet state of the chloro analogue is involved in the reaction. Since several radical intermediates, particularly n-complexes of chlorine radical, are identified in the laser flash photolysis of 2-chloro-N-pyridinylbenzamide, an intramolecular cyclization mechanism of phenyl radical assisted with n-complexation of chlorine radical for the cyclization reaction is proposed: the triplet state (78 kcal/mol) of the chloro analogue (1a), which is populated by the excitation of 1a undergoes a homolytic cleavage of the C-Cl bond to give phenyl and chlorine radicals; while chlorine radical holds the neighbor pyridinyl ring with its n-complexation, the intramolecular arylation of the phenyl radical with the pyridinyl ring proceeds to produce a conjugated 2,3-dihydropyridinyl radical and then the conjugated radical aromatizes to afford a cyclized product, benzo[c]naphthyridinone by ejecting a hydrogen. The photoreduction product can be formed by hydrogen atom abstraction of the phenyl sigma radical from the environment.

High quality magnesium doped GaN epitaxial layers on sapphire substrate were achieved by the rotating disk MOCVD. Energy levels of these acceptors were investigated by temperature dependent photoluminescence measurements. Magnesium concentration was varied from

Excited and ground state proton transfer reactions as well as other photophysical behaviors such as triplet state dynamics are studied for 6-hydroxyquinoline adsorbed in zeolite cages by measuring picosecond fluorescence kinetic profiles, microsecond transient reflectance kinetic profiles, emission spectra, and diffuse reflectance spectra. Protropic equilibrium species of 6-hydroxyquinoline undergo photon-initiated proton transfer cycles in catalytically important zeolite systems. In dehydrated zeolite surface, proton transfer reactions are much slower than those in aqueous solutions but also deprotonation is completed faster than protonation in the first excited singlet state as well as in the ground state. Protonation reaction in the excited state occurs only when the nitrogen atom of the molecule is located near a proton of zeolite surface otherwise the molecule relaxes downward.

Photochromic compound-conjugated fluorescent fullerene-silica nanoparticles prepared by the reverse-microemulsion method was utilized for photoswitchable cellular imaging by repeatable irradiation of ultraviolet and visible light.

Nanotechnology is regarded as the enabling technology of the 21st century. However, only a relatively small number of nano-enabled medical and healthcare products finally made their way to the market. There are several reasons why such innovative approaches fail in translation, with one key factor being the uncertainty surrounding their safety assessment. Although well described, interference reactions of engineered nanomaterials (ENM) with classical cytotoxicity assays remain a major source of uncertainty., Flow cytometry is a powerful, widely used, in vitro technique. Its readout is based on the detection of refracted laser light and fluorescence signals. It is therefore susceptible to ENM interference. Here we investigated possible interferences of ENM in the Annexin V/propidium iodide (PI) assay, which quantifies apoptotic and necrotic cell populations by flow cytometry., Two case studies were conducted using either silica or gold nanoparticles differing in size, specific surface area and surface chemistry. Both ENM types were found to cause distinct interference reactions at realistic concentrations. Silica particles induced false-positive signals; however only in the absence of a protein corona and in conjunction with a particular fluorophore combination (FITC/PI). In contrast, gold particles led to complex quenching effects which were only marginally influenced by the presence of proteins and occurred for both fluorophore combinations analyzed. We present a versatile spike-in approach which is applicable to all ENM and cell types. It further allows for the identification of a broad range of different interference phenomena, thereby increasing the reliability and quality of flow cytometry and ENM hazard assessment.

The photophysical properties of 4-acetylbiphenyl (ACBP) in various solvents and in aqueous α-cyclodextrin (α-CD) solution have been investigated using steady-state and time-resolved fluorescence spectroscopy. In non-polar solvents, the fluorescence spectrum with an emission maximum at 310 nm exhibits a vibrational structure with a non-mirror image to the absorption spectrum, reflecting the change in excited-state geometry toward the coplanarity of the biphenyl moiety. As the solvent polarity increases, the fluorescence spectrum denotes the structureless normal emission and an additional large Stokes' shift band around 380 nm. This behavior indicates the formation of an intramolecular charge transfer (ICT) state through relaxation from the normal excited state where the excited-state geometry change is hindered. Especially in water, the ICT emission is further red shifted to 400 nm with the normal emission band at 310 nm, and the relative intensities between 310 and 400 nm emission bands are affected by the excitation wavelength. However, this excitation wavelength dependence is not so large in organic polar solvents and aqueous α-CD solutions. The 400 nm emission in water exhibits a single exponential decay with a very short decay time (34 ps) while it shows a bi-exponential or triple-exponential decay in organic solvents and aqueous α-CD solutions. These results suggest that the ICT state in water is stabilized through exciplex formation by the hydrogen-bonding interaction between the acetyl group and water. © 1997 Elsevier Science S.A.

Silver nanoparticles are known to be distributed in many tissues after oral or inhalation exposure. Thus, understanding the tissue clearance of such distributed nanoparticles is very important to understand the behavior of silver nanoparticles in vivo. For risk assessment purposes, easy clearance indicates a lower overall cumulative toxicity. Accordingly, to investigate the clearance of tissue silver concentrations following oral silver nanoparticle exposure, Sprague–Dawley rats were assigned to 3 groups: control, low dose (100 mg/kg body weight), and high dose (500 mg/kg body weight), and exposed to two different sizes of silver nanoparticles (average diameter 10 and 25 nm) over 28 days. Thereafter, the rats were allowed to recover for 4 months. Regardless of the silver nanoparticle size, the silver content in most tissues gradually decreased during the 4-month recovery period, indicating tissue clearance of the accumulated silver. The exceptions were the silver concentrations in the brain and testes, which did not clear well, even after the 4-month recovery period, indicating an obstruction in transporting the accumulated silver out of these tissues. Therefore, the results showed that the size of the silver nanoparticles did not affect their tissue distribution. Furthermore, biological barriers, such as the blood–brain barrier and blood-testis barrier, seemed to play an important role in the silver clearance from these tissues.