A NIR fluorescent probe based on phenazine with a large Stokes shift for the detection and imaging of endogenous H2O2 in RAW 264.7 cells.

Hydrogen peroxide (H2O2), one of the reactive oxygen species (ROS), plays vital roles in diverse physiological processes. Thus, herein, to improve the signal-to-noise ratio, a new near-infrared region (NIR) fluorophore (PCN) based on reduced phenazine was developed. PCN was further designed as a "turn on" fluorescent probe (PCN-BP) for the detection of H2O2 by introducing p-boratebenzyl. After H2O2 was added, the p-boratebenzyl group in PCN-BP was oxidized to p-hydroxy benzyl; it then self-departed, forming PCN, which displayed 24-fold NIR emission at 680 nm with a large Stokes shift (more than 200 nm). This probe presented an excellent linear relation with the concentration of H2O2 and good selectivity to various ions, ROS and biothiols; thus, it can be utilized as a colorimetric and fluorescence turn-on probe. More importantly, the probe was also employed for the exogenous and endogenous imaging of H2O2 in RAW 264.7 cells.

ACQ-to-AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two-Photon NIR Bioimaging.

The traditional design strategies for highly bright solid-state luminescent materials rely on weakening the intermolecular π-π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid-state fluorescence. TBP-e-TPA with a molecular rotor in the end position of a planar core adopts a long-range cofacial packing mode, which in the solid state is almost non-emissive. By shifting molecular rotors to the bay position, the resultant TBP-b-TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid-state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP-b-TPA nanoparticles were used for two-photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid-state fluorophores.

Response to photo-oxidative stress of Pseudomonas aeruginosa PAO1 mutants impaired in different functions.

Clinicians often have to deal with infections that are difficult to control because they are caused by superbugs resistant to many antibiotics. Alternatives to antibiotic treatment include antimicrobial photodynamic therapy (aPDT). The photodynamic process causes bacterial death, inducing oxidative stress through the photoactivation of photosensitizer molecules in the presence of oxygen. No PDT-resistant bacteria have been selected to date, thus the response to photo-oxidative stress in non-phototrophic bacteria needs further investigation. The opportunistic pathogen Pseudomonas aeruginosa, in particular, has been shown to be more tolerant to PDT than other micro-organisms. In order to find any genetic determinants involved in PDT-tolerance, a panel of transposon mutants of P. aeruginosa PAO1 involved in the quorum sensing signalling system and membrane cytoplasmic transport were photoinactivated as part of this study. Two pseudomonas quinolone signalling (PQS) knock-out mutants, pqsH- and pqsC-, were as PDT-sensitive as the PAO1 wild-type strains. Two PQS hyperproducer variants, pqsA- and rsaL-, were shown to be more tolerant to photo-oxidative stress than the wild-type strain. In the pqsA- mutant, the hyperpigmentation due to the presence of phenazines could protect cells against PDT stress, while in rsaL- no pigmentation was detectable. Furthermore, a mutant impaired in an ATP-binding cassette transport involved in maintaining the asymmetry of the outer membrane was significantly more tolerant to photo-oxidative stress than the wild-type strain. These observations support the involvement of quorum sensing and the importance of the bacterial cell envelope when dealing with photo-oxidative stress induced by photodynamic treatment.

Modified Indulines: From Dyestuffs to In Vivo Theranostic Agents.

The efficient, versatile, and straightforward synthesis of the first N-alkyl analogues of induline 3B (8a and 8b) is reported. Thanks to the introduction of lipophilic substituents and their attractive photophysical properties (far-red emission and production of singlet oxygen), phenazinium 8b can be used as a theranostic agent and shows, at very low concentrations (100 nM), a remarkable ability to (i) image cells and zebrafish embryos with high quality under both mono- (514 nm) and biphotonic (790 and 810 nm) excitations, (ii) efficiently and quickly penetrate cancer cells rather than healthy fibroblasts, and (iii) induce a total or almost total cancer cell death in vitro and in vivo after illumination (λexc = 540-560 nm). The molecular structure of 8b is based on a triamino-phenazinium core only, with no need for additional components, highlighting the emergence of a minimalistic and versatile class of fluorescent probes for targeted photodynamic cancer therapy.

[Dependence of the rate of safranine photocatalytic destruction on the catalyst concentration].

The effect of the concentration of disperse titanium-containing oxide photocatalyzers on the destruction of safranine in aqueous solutions has been studied. It was found that the rate constant of safranine destruction increases with the content of the catalyzer in solution and reaches a maximum value at a catalyzer concentration of < or = 3 g/l, after which it depends no longer on the catalyzer concentration. The flattening of the rate constant curve is caused by light scattering and the narrowing of the reaction scope due to an increase in the optical density of the solution. In the region where the rate constant increases with the catalyzer concentration, the rise in the rate constant is determined by an increase in the specific area of the catalyzer; in the region of the plateau, the rate constant is practically independent on the specific area of the catalyzer.

Efficient photocatalytic removal of safarnin-O dye pollutants from water under sunlight using synthetic bentonite/polyaniline@Ni2O3 photocatalyst of enhanced properties.

This study involves a synthesis of bentonite/polyaniline composite (BE/PANI) of enhanced physicochemical properties as catalyst support for Ni2O3 photocatalyst. The change in the structural properties, morphological features, and optical behavior was addressed utilizing several analytic techniques. The characterization results reflected considerable enhancement in the specific surface area after the integration between bentonite and polyaniline (127 m2/g) and after loading of the campsite by Ni2O3 forming bentonite/polyaniline@Ni2O3 composite (BE/PANI@Ni2O3) (231 m2/g). Additionally, the band gap energy was reduced to 2.41 eV and 1.61 eV for BE/PANI and BE/PANI@Ni2O3, respectively, as compared to that of 3.4 eV for pure Ni2O3. The photocatalytic removal of safranin-O dye under sunlight exposure using BE/PANI@Ni2O3 as catalyst revealed great enhancement in the removal percentages by 63%, 75%, and 72.35% higher than bentonite, polyaniline, and Ni2O3, respectively. Five milligrams per liter of safranin-O dye can be completely removed from 100 ml water using 0.05 g of the composite after 90 min. The catalyst also was applied effectively in the removal of safranin-O dye from raw water samples as a realistic application of the synthetic composite. Synthetic BE/PANI@Ni2O3 as photocatalyst showed very high stability and can be used seven times as photocatalytic at amazing removal percentages.

Photochemical degradation of the hazardous dye Safranin-T using TiO2 catalyst.

Aqueous solutions of Safranin-T, a hazardous textile dye, are photodegraded under ultraviolet light using TiO2 as catalyst. The process has been carried out at different pHs, amounts of catalyst, concentrations of the dye, and effects of the electron acceptor H2O2. It is found that under the influence of TiO2 as catalyst the colored solution of the dye Safranin-T becomes colorless and the process follows first-order reaction kinetics. The optimum conditions for the degradation of the dye have been found as 5.0x10(-5) M dye concentration, pH 5.7, and 12 mg catalyst dose. In order to evaluate the effect of the electron acceptor, the effect of H2O2 on the degradation process is also monitored and it is found that generation of hydroxyl radicals and retardation of electron-hole recombination takes place. Measuring chemical oxygen demand also monitors the toxicity of the degraded dye solution and a significant decrease is observed, which implies that the photodegradation through TiO2 is a safer technique.

[Study of the kinetics of chlorophyll photosensitized dye reduction by photopolarography]. / Izuchenie kinetiki fotosensibilizirovannogo khlorofillom vosstanovleniia krasitelei metodom fotopoliarografii.

It has been shown by photopolarographic method that under stationary illumination chlorophyll-photosensitized reduction of dyes with ascorbic acid proceeds according to the first kinetic order. Rate constants of photoreduction of vitamin K3, methelene red, safranin-T and methylviologen were found in the course of sensitization which proceeded by oxidative and reduction mechanisms. Similarity of kinetics at both sensitization mechanisms was shown. Results obtained by polarographic and spectroscopic methods were compared.

Magnetic field effect on photoinduced electron transfer between dibenzo[a,c]phenazine and different amines in acetonitrile-water mixture.

Unlike the simple phenazine (PZ) molecule, one of its derivatives, dibenzo[a,c]phenazine (DBPZ) forms a charge-transfer complex in the triplet state (3ECT) with different amines, e.g., N,N-dimethylaniline (DMA), 4,4'-bis(dimethylamino)diphenylmethane (DMDPM), and triethylamine (TEA). Formation of the 3ECT and radical ion pairs (RIPs) due to electron transfer is identified by laser flash photolysis. The RIPs are much more abundant in the cases of DMA and DMDPM rather than in TEA. Interestingly, a prominent magnetic field effect (MFE) is observed in both the cases of 3ECT and RIPs in homogeneous acetonitrile-water (MeCN/H2O) mixtures. This rare observation of the 3ECT and MFE in non-viscous medium could be explained by considering the extended planar structure of DBPZ and inter-radical hydrogen bonding, mediated by the intervening water molecules. The magnetic field behavior is consistent with the hyperfine mechanism; however, the low B1/2 value for DBPZ-TEA system is ascribed to fast electron exchange due to the close proximity of the corresponding radical ions.

The sensitivity to light of solutions of phenazine methosulphate: a quantitative cytochemical study.

The ability of phenazine methosulphate to transfer electrons from reduced coenzymes to a tetrazolium salt, neotetrazolium chloride, after exposure to light for various periods of time has been studied. Enzymes assayed for this purpose were: glucose-6-phosphate dehydrogenase been studied. Enzymes assayed for this purpose were: glucose-6-phosphate dehydrogenase (NADP+-dependent); lactate dehydrogenase (NAD+-dependent) and succinate dehydrogenase (flavoprotein-dependent). Enzyme activity was measured in sections of rodent liver by scanning and integrating microdensitometry. Phenazine methosulphate in solution was found to be sufficiently stable in light for up to two hours for reproducible quantitative measurements of cytochemical dehydrogenase activity to be obtained over this period.