Water-Soluble Organic Nanoparticles with Programable Intermolecular Charge Transfer for NIR-II Photothermal Anti-Bacterial Therapy.

Extensive recent efforts have been put on the design of high-performance organic near-infrared (NIR) photothermal agents (PTAs), especially over NIR-II bio-window (1000-1350 nm). So far, the development is mainly limited by the rarity of molecules with good NIR-II response. Here, we report organic nanoparticles of intermolecular charge-transfer complexes (CTCs) with easily programmable optical absorption. By employing different common donor and acceptor molecules to form CTC nanoparticles (CT NPs), absorption peaks of CT NPs can be controllably tuned from the NIR-I to NIR-II region. Notably, CT NPs formed with perylene and TCNQ have a considerably red-shifted absorption peak at 1040 nm and achieves a good photothermal conversion efficiency of 42 % under 1064 nm excitation. These nanoparticles were used for antibacterial application with effective activity towards both Gram-negative and Gram-positive bacteria. This work opens a new avenue into the development of efficient PTAs.

Stable photoinduced charge separation in heptacene.

Heptacene, generated in inert gas matrices by photobisdecarbonylation of a bridged alpha-diketone precursor, undergoes ionization into radical anion and radical cation upon UV irradiation.

Irreversible oxidative inactivation of protein kinase C by photosensitive inhibitor calphostin C.

Isolated protein kinase C (PKC) was irreversibly inactivated by a brief (min) incubation with calphostin C in the presence of light. This inactivation required Ca2+ either in a millimolar range in the absence of lipid activators or in a submicromolar range in the presence of lipid activators. In addition, an oxygen atmosphere was required suggesting the involvement of oxidation(s) in this inactivation process. Furthermore, PKC inactivation might involve a site-specific oxidative modification of the enzyme at the Ca(2+)-induced hydrophobic region. Physical quenchers of singlet oxygen such as lycopene, beta-carotene, and alpha-tocopherol all reduced the calphostin C-induced inactivation of PKC. In intact cells treated with calphostin C, the inactivation of PKC was rapid in the membrane fraction compared to cytosol. This intracellular PKC inactivation was also found to be irreversible. Therefore, calphostin C can bring prolonged effects for several hours in cells treated for a short time. Taken together these results suggest that the calphostin C-mediated inactivation of PKC involves a site-specific and a 'cage' type oxidative modification of PKC.

Photosensitization with anticancer agents. 20--EPR studies on the photodynamic action of phleichrome: formation of semiquinone radical and activated oxygen species on illumination with visible light.

When phleichrome was illuminated with visible light, the semiquinone radical, singlet oxygen, and superoxide anion radical were detected. The formation of the semiquinone radical and activated oxygen species and the transformations and competitions between them depend on quinone and oxygen concentration, duration and intensity of illumination, and the nature of the substrate. In anaerobic solution, the semiquinone radical was predominantly photoproduced via the self-electron transfer between the excited and ground species. In contrast, in aerobic solution, singlet oxygen is the principal product in the photosensitization of phleichrome. In addition to singlet oxygen, superoxide anion radical is also generated by the quinones upon illumination in aerobic solution, but to a lesser extent. The generation of the superoxide anion is significantly enhanced by the presence of electron donors.

Mutation of Chinese hamster cells by near-UV activation of promutagens.

A tissue-culture assay for mutagenesis and cytotoxicity incorporating near ultraviolet (NUV) light activation of polyaromatic hydrocarbons (PAH) has been developed. Cultures of Chinese hamster cells (line CHO) growing in suspension culture were inoculated with benzo[a]pyrene (B[a]P), 7,12-dimethylbenzanthracene (DMBA) of shale-oil retort-water and exposed to light from a high-pressure mercury lamp fitted with a Corning NUV bandpass filter. This light source both permitted activation of PAH and the shale-oil water and preculded detectable damage to DNA. Neither the PAH nor the NUV alone had any effect on cell survival or mutation frequencies but the chemicals plus NUV were extremely effective in producing mutations to 6-thioguanine resistance (hgprt gene).

Radiation damage in coronene, rubrene and p-terphenyl, measured for incident electrons of kinetic energy between 100 and 200 kev.

We have measured the sensitivity of three highly conjugated organic compounds to electron irradiation. Using a 200 keV TEM, loss of crystallinity was determined from quantitative electron-diffraction measurements. Degradation of the molecular ring structure was monitored from fading of the 6 eV pi-excitation peak in the energy-loss spectrum. Measurements at incident energies between 30 keV and 100 eV were made using a scanning electron microscope (SEM), by recording gradual decay of the cathodoluminescence (CL) signal. Expressed in Grays, the energy dose required for CL decay in coronene is a factor of 30 lower than for destruction of crystallinity and a factor of 300 lower than for destruction of the molecular structure. Below 1 keV, the CL-decay cross section shows no evidence of a threshold effect, indicating that the damage involved is caused by valence-electron (rather than K-shell) excitation. Therefore even relatively radiation-resistant organic materials may undergo some form of damage when examined in a low-energy electron microscope or a low-voltage SEM.

Mutagenicity of photochemical reaction products of polycyclic aromatic hydrocarbons with nitrite.

Six kinds of polycyclic aromatic hydrocarbons (PAHs) were subjected to ultraviolet light irradiation with nitrite for 1, 4, 8 and 24 h, and the irradiated samples were tested for mutagenicity towards Salmonella typhimurium TA 98, TA 100 and TA 1538. Irradiated samples of pyrene, fluoranthene and benzo[a]pyrene showed marked mutagen responses towards TA 98 and TA 1538, especially in the absence of S9 mix. The direct-acting mutagenic activity of these samples, showing high activities at 1-8 h, decreased greatly with the development of irradiation. Further, these direct-acting mutagens were mostly present in the neutral fraction. On the other hand, the mutagenicity of the irradiated sample of 5,6-benzoquinoline was high both with and without S9 mix, and was mostly present in the basic fraction because of its authentic characteristic. There was no correlation between the yield of 1-nitropyrene and the mutagenic activity of the photochemical reaction product of pyrene with nitrite. Further studies by TLC separation suggested that a considerable number of direct-acting mutagens formed in this experiment were more polar than nitrated PAH such as 1-nitropyrene.

[Distribution, formation, carcinogenic and mutagenic activities of nitro derivatives of polycyclic aromatic hydrocarbons]. / Raspredelenie, obrazovanie, kantserogennaia i mutagennaia aktivnost' nitroproizvodnykh politsiklicheskikh aromaticheskikh uglevodorodov.

Nitro-PAHs (nitro-substituted derivatives of polycyclic aromatic hydrocarbons) are a class of chemical compounds with high biologic activity. They have been detected in samples of air pollutants, diesel and gasoline engine exhausts, in airplane exhaust emissions, cigarette smoke condensate, emissions of coke ovens, wood-burning fireplaces, coal-fired plants, in food and tea. Concentrations of nitro-PAHs have been compared with those of PAHs present in air pollutant samples and emissions from different sources. Information on the environmental occurrence, formation, and decomposition of nitro-PAHs in the atmosphere is given. Biologic effects (carcinogenic and mutagenic) of pure nitro-PAHs and nitro-PAHs-containing complex mixtures are discussed.

A preliminary study of the changes in the direct-acting mutagenicities of several nitropolycyclic aromatic hydrocarbons after exposure under sunlight.

Five commercially available nitropolyclyclic aromatic hydrocarbons (nitro-PAH), namely, 4-nitrobiphenyl, 2-nitrofluorene, 9-nitroanthracene, 1-nitropyrene, and 2,7-dinitrofluorene, were exposed under restricted sunlight in the open air. The direct-acting mutagenicities of the samples after an exposure of 45 days were measured in order to compare them with those of the original samples in the Ames Salmonella typhimurium bioassay. It was found that the mutagenicities of some nitro-PAH do not change significantly while the mutagenicities of others increase or decrease after exposure. A preliminary study of nitro-PAH reaction products after exposure using GC, GC/MS, and FT-IR is also reported.

[Decomposition of polycyclic aromatic hydrocarbons by means of radiation]. / Décomposition par irradiation des hydrocarbures aromatiques polycycliques.

BaP decomposes rapidly after exposure to solar illuminations or in simulated atmosphere. The kinetics of degradation depend upon the nature of the support material, the radiant energy, the light wavelength and the presence of other components in the mixture on the same support.

Photooxidation products of polycyclic aromatic compounds containing sulfur.

Photooxidation of crude oil components is an important process that removes pollutants from the environment. Polycyclic aromatic compounds (PACs) are known to be toxic to many life forms, but little is known about their photooxidation products in the aqueous phase. We here identify a large number of photoproducts from 11 benzothiophenes, a polycyclic aromatic sulfur heterocycle that is a major representative of PACs in crude oil. The investigated compounds contain two to four methyl groups and an ethyl or an n-octyl group. In water, the products arise through oxidation of alkyl side chains to aldehydes and carboxylic acids or through an opening in one of the aromatic rings. The product analysis was performed using gas chromatography with mass spectrometric or atomic emission detection. The main product is always a sulfobenzoic acid, which strongly lowers the pH of the solution. With long alkyl substituents, surfactants are formed, which may possess solubilizing properties in water. The larger the number of alkyl groups, the faster is the photooxidation. Several of the identified acidic compounds were also found when whole crude oil was photooxidized, showing that simulation with individual compounds reflects the situation in whole crude.

Laser flash photolysis of 1,2-diketopyracene and a theoretical study of the phenolic hydrogen abstraction by the triplet state of cyclic alpha-diketones.

Laser flash photolysis (LFP) studies, atoms in molecules (AIM) studies, and density functional theory (DFT) calculations have been performed in order to study the mechanism of the hydrogen abstraction by alpha-diketones in the presence of phenols. Laser irradiation of a degassed solution of 1,2-diketopyracene in acetonitrile resulted in the formation of a readily detectable transient with absorption at 610 nm, but with very low absorptivity. This transient decays with a lifetime of around 2 micros. The quenching rate constant for substituted phenols, kq, ranged from 1.10x10(8) L mol-1 s-1 (4-cyanophenol) to 3.87x10(9) L mol-1 s-1 (4-hydroxyphenol). The Hammett plot for the reaction of the triplet of 1,2-diketopyracene with phenols gave a reaction constant rho=-0.9. DFT calculations (UB3LYP/6-311++G**//UB3LYP/6-31G*) of the triplet complex ketone-phenol revealed that hydrogen transfer has predominantly occurred and that the reaction with alpha-diketones are generally 7 kcal/mol less endothermic than the respective reactions of the monoketones. These results together with the geometries obtained from the DFT calculations, natural bond order (NBO) analysis, and AIM results indicate that hydrogen abstraction for alpha-diketones is facilitated by the electrophilicity of the ketone, instead of neighboring group participation by the second carbonyl group.

Photochemical tuning of light emission in a conjugated polymer containing norbornadiene units in the main chain.

A conjugated alternating copolymer containing norbornadiene and bis(ethynylene)phenylene units was prepared by the Cassar-Heck-Sonogashira cross-coupling reaction. Its electroluminescence was tested in a device, and its fluorescence colour could be tuned by light-induced norbornadiene-quadricyclane isomerization.

Radiation damage in electron microscopy of organic materials: effect of low temperatures.

As measured by the life-time of their electron diffraction patterns, the radiation sensitivity of anthracene and coronene at 500 kV is reduced by a factor of three to four at liquid helium temperature in comparison to room temperature, For l-valine the ratio is about 1-8 but there is a wide variation in the results, possibly due to differences in crystal thickness. The end-dose at 20 degrees K for valine is equivalent to 13 electrons/A2; for anthracene and coronene it is about 600 electrons/A2 at room temperature. The variation of end-dose with temperature shows that at least two mechanisms must be involved in damage to such compounds, possibly concerning the breaking of intermolecular and intramolecular bonds, respectively.

Photoisomerization of a rotaxane hydrogen bonding template: light-induced acceleration of a large amplitude rotational motion.

Establishing methods for controlling aspects of large amplitude submolecular movements is a prerequisite for the development of artificial devices that function through rotary motion at the molecular level. Here we demonstrate that the rate of rotation of the interlocked components of fumaramide-derived [2]rotaxanes can be accelerated, by >6 orders of magnitude, by isomerizing them to the corresponding maleamide [2]rotaxanes by using light.

Solvent-induced photodegradation as a source of error in the analysis of polycyclic aromatic hydrocarbons.

The photodegradation of seven common polycyclic aromatic hydrocarbons (PAHs) has been examined in a range of organic solvents. Reactions followed a first order equation with benzo[a]pyrene and benzo[a]anthracene being the most rapidly photodegraded. Generally, the more polar the solvent the faster is the degradation process. A number of photodegradation products were identified by gas chromatography-mass spectrometry. The identification of compounds such as 4-amino-1-naphthalenecarbonitrile and 1H,3H-naphtho[1,8-cd]pyran-1-one clearly indicated that the solvent molecules have taken part in the formation of these compounds. Solvent-induced photodegradation is shown to be an important consideration in choosing the optimum solvent for the best analytical recoveries of PAHs from various matrices.