1O2 Quantum Yield Research Articles

DSPE-PEG-Coated Uniform Nitrogen-Doped Carbon Capsules for NIR-Mediated Synergistic Chemophototherapy of Skin Cancer.

Uniform monodispersed nitrogen-doped carbon spheres have been emerging as an exciting platform for multipurpose medical applications like photothermal therapy and photoacoustic imaging and as carriers for aromatic anticancer drugs. However, synthesis of uniform N-doped mesoporous carbon of size less than 100 nm with reasonable photothermal and photodynamic activities is a challenging task. In this connection, the present paper reports synthesis of nitrogen-doped mesoporous carbon spheres (NMCSs) from five different copolymers of pyrrole and substituted aniline (-H, o-NH2, m-NH2, p-NH2, and m-NO2) using a soft template approach. It has been found that NMCSs synthesized from poly(pyrrole-co-m-nitroaniline) show uniform mesoporous particles of size 80 nm, a photothermal conversion efficiency η of 52.7%, and an average 1O2 quantum yield of 20% under exposure of a 980 nm NIR laser. With a high η of 52%, a multifunctional nanodrug has been formulated by loading 5-Fu in NMCS. The overall drug-loaded NMC was encapsulated by thermosensitive DSPE-PEG to improve translocation of the particle in the cell and thermosensitive drug release. A reliable release of anticancer drug 5-Fu (78%) has been achieved in 50 h in lysosomal conditions under 980 nm laser exposure. This NMC-5-Fu-DSPE-PEG nanodrug produces reactive oxygen species and enhances the therapeutic effect in comparison with free drug under an NIR laser as verified in B16F0 melanoma cells.

Unveiling the photophysical, biomolecule binding and photo-oxidative capacity of novel Ru(II)-polypyridyl corroles: A multipronged approach

Two fluorinated corrole derivatives, namely H3MebpyCor and RuMebpyCor, were synthesized and characterized in terms of their photophysical, electrochemical, and photooxidation behavior. Their biomolecular binding capacity toward Human Serum Albumin (HSA) and calf thymus DNA (CT-DNA) was also evaluated. The experimental data were correlated with theoretical analysis via Time Dependent Density Functional Theory (TDDFT) and Molecular Docking calculations. We found an extremely low fluorescence quantum yield for both corroles dissolved in acetonitrile (CH3CN) and dimethyl sulfoxide (DMSO), which suggests a relaxation pathway through nonradiative processes, such as internal conversion. However, the internal conversion channel in RuMebpyCor competes with the energy transfer to the Ru(II) moiety, placing triplet state formation as a second mechanism of relaxation for this structure. Both corroles showed no aggregation and good photostability. The singlet oxygen (1O2) quantum yield (ΦΔ) values also highlight their potential application in photoinactivation approaches. Theoretical analysis suggests that the introduction of Ru(II) ion coordinated in the bipyridyl unit significantly alters the optically induced electronic transitions, and that the solvents play an important role in defining the optical spectra of the two corroles. Additionally, they interact spontaneously and moderate to strong via ground-state association (static process) with HSA and CT-DNA. However, for the HSA binding assays the dynamic fluorescence quenching mechanism can also occur at high corrole concentrations. Finally, in silico calculations suggest that the main binding region into CT-DNA is the minor groove, while subdomain IIA (site I) is the main binding region for HSA:H3MebpyCor (experimental proportion 1:1) and both subdomains IIA and IB (sites I and III, respectively) for HSA:RuMebpyCor (experimental proportion 1:2).

Molecular characteristics of the photosensitizer TONS504: Comparison of its singlet oxygen quantum yields and photodynamic antimicrobial effect with those of methylene blue.

TONS504 (C51H58O5I2) is a chlorin derivative that exhibits a photodynamic antimicrobial effect (PAE) on various infectious keratitis pathogens. However, the molecular characteristics of TONS504 are not well understood. This study aimed to investigate the molecular characteristics of TONS504 by comparing its singlet oxygen (1O2) quantum yields and PAE with those of methylene blue (MB). To measure the 1O2 quantum yields, TONS504 and MB were dissolved in phosphate-buffered saline and phosphate-buffered saline containing 1% Triton X-100. The solutions were then activated by a Nd:YAG laser with an average output power of 8mW. Near-infrared 1O2 luminescence was detected as an indicator of the 1O2 quantum yields. To evaluate the PAE, TONS504 and MB were activated by a light-emitting diode with a total light energy of 30J/cm2. We compared the minimum molar concentration of each photosensitizer to show apparent PAEs on Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. TONS504 exhibited higher 1O2 quantum yields than MB in PBS/Triton X-100 but not in PBS. S. aureus and C. albicans were reduced by TONS504 at lower concentrations than by MB, but this was not the case for P. aeruginosa. Our results provide insight on the molecular characteristics of TONS504 and suggest that TONS504 has excellent 1O2 quantum yields and PAE. Compared with MB, TONS504 in PBS has stronger efficacy toward some infectious keratitis pathogens but not others.

An Approach to Developing Cyanines with Simultaneous Intersystem Crossing Enhancement and Excited-State Lifetime Elongation for Photodynamic Antitumor Metastasis.

Heavy-atom-based photosensitizers usually exhibit shortened triplet-state lifetimes, which is not ideal for hypoxic tumor photodynamic therapy. Although several heavy-atom-free photosensitizers possess long triplet-state lifetimes, the clinical applicability is limited by their short excitation wavelengths, poor photon capture abilities, and intrinsically hydrophobic structures. Herein we developed a novel NIR heavy-atom-free photosensitizer design strategy by introducing sterically bulky and electron-rich moieties at the meso position of the pentamethine cyanine (Cy5) skeleton, which simultaneously enhanced intersystem crossing (ISC) and prolonged excited-state lifetime. We found that the 1O2 generation ability is directly correlated to the electron-donating ability of the meso substituent in cyanine, and the excited-state lifetime was simultaneously much elongated when the substituents were anthracene derivatives substituted at the 9-position. Our star compound, ANOMe-Cy5, exhibits intense NIR absorption, the highest 1O2 quantum yield (4.48-fold higher than Cy5), the longest triplet-state lifetime (9.80-fold longer than Cy5), and lossless emission intensity (nearly no change compared with Cy5). Such excellent photophysical properties coupled with its inherently cationic and hydrophilic nature enable the photosensitizer to realize photoablation of solid tumor and antitumor lung metastasis. This study highlights the design of a new generation of NIR photosensitizers for imaging-guided photodynamic cancer treatment.

Estimation of Singlet Oxygen Quantum Yield Using Novel Green-Absorbing Baird-type Aromatic Photosensitizers.

We report two new organic green-absorbing singlet oxygen (1 O2 ) photosensitizers: Quinoidal naphthyl thioamide (QDM) and bis-iodol-dipyrrolonaphthyridine-dione (I2 -DPND), with triplet energies of 40.8 and 47.5 kcal mol-1 (at 77 K in a glassy matrix) , respectively. The UV-vis absorption and emission characteristics of QDM and I2 -DPND are similar to other commercially available organic 1 O2 photosensitizers such as Rose Bengal, which was used as standard/reference to estimate the 1 O2 quantum yield (Φ∆ ) of the chromophores under study. Using 9,10-diphenylanthracene (DPA) as an 1 O2 quencher, we estimated the Φ∆ ≈ 67-85% for QDM and Φ∆ ≈ 25-32% for I2 -DPND. The discrepancy in the Φ∆ values could be explained by the apparent photo-decomposition of the later dye. Nevertheless, the high Φ∆ value for QDM is unprecedented, as this chromophore exhibits relatively low structural complexity and could further be derivatized to create novel photodynamic agents.

Synthesis, Spectroscopic, and 1O2 Sensitization Characteristics of Extended Pd(II) 10,10-Dimethylbiladiene Complexes Bearing Alkynyl-Aryl Appendages.

Photodynamic therapy (PDT), which involves the photoinduced sensitization of singlet oxygen, is an attractive treatment for certain types of cancer. The development of new photochemotherapeutic agents remains an important area of research. Macrocyclic tetrapyrrole compounds including porphyrins, phthalocyanines, chlorins, and bacteriochlorins have been pursued as sensitizers of singlet oxygen for PDT applications but historically are difficult to prepare/purify and can also suffer from high nonspecific dark toxicity, poor solubility in biological media, and/or slow clearance from biological tissues. In response to these shortcomings, we have developed a series of novel linear tetrapyrrole architectures complexed to late transition metals as potential PDT agents. We find that these dimethylbiladiene (DMBil1) tetrapyrrole complexes can efficiently photosensitize generation of 1O2 oxygen upon irradiation with visible light. To extend the absorption profile of the DMBil1 platform, alkynyl-aryl groups have been conjugated to the periphery of the tetrapyrrole using Sonogashira methods. Derivatives of this type containing ancillary phenyl (DMBil-PE), naphthyl (DMBil-NE), and anthracenyl (DMBil-AE) groups have been prepared and characterized. In addition to structurally characterizing Pd[DMBil-NE] and Pd[DMBil-AE], we find that extension of the tetrapyrrole conjugation successfully red-shifts the absorption of the DMBil-Ar family of biladienes further into the phototherapeutic window (i.e., 600-900 nm). Photochemical sensitization studies demonstrate that our series of new palladium biladiene complexes (Pd[DMBil-Ar]) can sensitize the formation of 1O2 with quantum yields in the range ΦΔ = 0.59-0.73 upon irradiation with light of λ ≥ 650 nm. The improved absorption properties of the Pd[DMBil-Ar] complexes in the phototherapeutic window, together with their high 1O2 quantum yields, highlight the promise of these compounds as potential agents for PDT.

Spatial effects of photosensitization on morphology of giant unilamellar vesicles

Singlet oxygen (1O2) formed through photosensitization may initiate oxidative destruction of biomembranes, however, the influence from the spatial organization of photosensitizers (PS) relative to membranes remains unclear. To clarify this issue, we loaded riboflavin 5′-(dihydrogen phosphate) monosodium (FMN-Na) as a hydrophilic PS into the lumen of halloysite nanotubes (HNTs), and attached the nanoassemblies (FMN-Na@HNTs), via Pickering effects, to the outer surfaces of giant unilamellar vesicles (GUVs) of phospholipids. We also prepared GUVs dopped with lumiflavin (LF) as a lipophilic PS having a 1O2 quantum yield comparable to FMN-Na. FMN-Na capsulated in HNT was characterized by a longer triplet excited state lifetime (12.1 μs) compared to FMN-Na free in solution (7.5 μs), and FMN-Na in both forms efficiently generated 1O2 upon illumination. The spatio-effects of PS on the photosensitized morphological changes of membranes were studied using conventional optical microscopy by monitoring GUV morphological changes. Upon light exposure (400–440 nm), the GUVs attached with FMN-Na@HNT merely experienced membrane deformation starting from the original spherical shape, ascribed to Type II photosensitization with 1O2 as oxidant. In contrast, photooxidation of LF dopped GUVs mainly led to membrane coarsening and budding assigned to Type I photosensitization. The spatial effects of PS on photosensitized morphological changes were related to the different lipid oxidation products generated through Type I and Type II photosensitized lipid oxidation.

Controlled Aggregation of a Perylene-Derived Probe for Near-Infrared Fluorescence Imaging and Phototherapy.

The design and synthesis of water-soluble phototherapeutic agents with near-infrared (NIR) fluorescence emission is highly desirable for cancer diagnosis and treatment. Here, we report the construction of an amphiphilic perylene-derived photosensitizer, AP. AP shows NIR emission with large Stokes shift (130 nm) and high 1O2 quantum yield (22%). It can self-assemble into nanoparticles in aqueous solution with quenched fluorescence emission due to aggregation-induced quenching. Upon membrane anchoring, AP is able to disassemble into free monomer molecules and specifically "light up" the cell membrane without the usually required washing procedures. Furthermore, AP is subsequently used for the efficient photodynamic therapy against cancer cells and solid tumors. The in vitro and in vivo experiments clearly indicate that AP is suitable for biological imaging and can serve as a promising photosensitizer for tumor suppression.

Protoporphyrin IX (PpIX) loaded PLGA nanoparticles for topical Photodynamic Therapy of melanoma cells

IntroductionNanoparticles (Np) can increase drug efficacy and overcome problems associated with solubility and aggregation in a solution of PpIX. PurposeEvaluate if Np interferes in the photophysical and photobiological capacity of the PpIX comparing with free PpIX intended for topical PDT of melanoma. MethodsIn vitro photophysical evaluation of Np-PpIX was carried out through singlet oxygen (1O2) quantum yield. In vitro cytotoxicity and phototoxicity assays have used murine melanoma cell culture. ResultsThe quantum yield of singlet oxygen has shown that Np did not influence the formation capacity of this reactive species. In the dark, all PpIX-Nps concentrations were less cytotoxic compared to free drugs. At a higher light dose (1500 mJ.cm2) 3.91 μg / mL PpIX had similar % viable cells for free and Np (∼34 %) meaning Nps did not interfere in the photodynamic effect of PpIX. However, at 7.91 μg / mL the phototoxicity increased for both (5.8 % viable cells for free versus 21.7 % for Nps). Despite the higher phototoxicity of free PpIX at this concentration, greater cytotoxicity in the dark was obtained (∼49 % viable cells for free versus ∼90.6 % Np) which means Nps protect the tumor tissue from the photodynamic action of PpIX. ConclusionsNp is a potential delivery system for melanoma skin cancer, since it maintained the photophysical properties of PpIX and excellent in vitro phototoxicity effect against melanoma cells, reducing cell viability ∼80 % (7.91 μg / mL PpIX in Nps) and provides safe PDT (due to lower cytotoxicity in the dark).

Determination of Singlet Oxygen Quantum Yield of a Porphyrinic Metal–Organic Framework

Metal–organic frameworks (MOFs) have emerged as heterogeneous photosensitizers in applications ranging from photodynamic therapy to photocatalysis. However, singlet oxygen (1O2) quantum yields of MOF photosensitizers are largely unknown. Herein, we report a reliable method to quantify the 1O2 quantum yield of a porphyrin MOF PCN-222/MOF-545 (free base). To accurately measure the optical density of the MOF suspensions in chloroform, a UV–vis spectrometer equipped with an integrating sphere detector was employed. However, no 1O2 near-infrared luminescence signal from the excited MOF could be detected and the amount of 1O2 produced by the MOF photosensitizer was quantified using a 1O2 trap 9,10-dimethylanthracene. Using C70 as a reference, the 1O2 quantum yield of PCN-222/MOF-545 (free base) was determined to be 0.35 ± 0.02. This method should be applicable to the determination of 1O2 quantum yields of other solid-state materials.

Synthesis of Sn nanocluster@carbon dots for photodynamic therapy application

Recently, photodynamic therapy (PDT) has been extensively applied in clinical and coadjuvant treatment of various kinds of tumors. However, the photosensitizer (PS) of PDT still lack of high production of singlet oxygen (1O2), low cytotoxicity and high biocompatibility. Herein, we propose a facile method for establishing a new core-shell structured Sn nanocluster@carbon dots (CDs) PS. Firstly, Sn4+@S-CDs complex is synthesized using the sulfur-doped CDs (S-CDs) and SnCl4 as raw materials, and subsequently the new PS (Sn nanocluster@CDs) is obtained after vaporization of Sn4+@S-CDs solution. Remarkably, the obtained Sn nanocluster@CDs show an enhanced fluorescence as well as a higher 1O2 quantum yield (QY) than S-CDs. The high 1O2 QY (58.3%) irradiated by the LED light (400–700nm, 40mW/cm2), induce the reduction of 4T1 cancer cells viability by 25%. More intriguingly, no visible damage happens to healthy cells, with little impact on liver tissue due to renal excretion, both in vitro and in vivo experiments demonstrate that Sn nanocluster@CDs may become a promising PS, owning a high potential for application in PDT.

An acid-triggered porphyrin-based block copolymer for enhanced photodynamic antibacterial efficacy

Bacterial infection, especially multidrug-resistant (MDR) bacterial infection has threatened public health drastically. Here, we fabricate an “acid-triggered” nanoplatform for enhanced photodynamic antibacterial activity by reducing the aggregation of photosensitizers (PSs) in bacterial acidic microenvironment. Specifically, a functional amphiphilic block copolymer was first synthesized by using a pH-sensitive monomer, 2-(diisopropylamino) ethyl methacrylate (DPA) and porphyrin-based methacrylate (TPPC6MA) with poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) as the macromolecular chain transfer agent, and POEGMA-b-[PDPA-co-PTPPC6MA] block copolymer was further self-assembled into spherical nanoparticles (PDPA-TPP). PDPA-TPP nanoparticles possess an effective electrostatic adherence to negatively charged bacterial cell membrane, since they could rapidly achieve positive charge in acidic bacterial media. Meanwhile, the acid-triggered dissociation of PDPA-TPP nanoparticles could reduce the aggregation caused quenching (ACQ) of the photosensitizers, leading to around 5 folds increase of the singlet oxygen (1O2) quantum yield. In vitro results demonstrated that the “acid-triggered” PDPA-TPP nanoparticles could kill most of MDR S. aureus (Gram-positive) and MDR E. coli (Gram-negative) by enhanced photodynamic therapy, and they could resist wound infection and accelerate wound healing effectively in vivo. Furthermore, PDPA-TPP nanoparticles could well disperse the biofilm and almost kill all the biofilm-containing bacteria. Thus, by making use of the bacterial acidic microenvironment, this “acid-triggered” nanoplatform in situ will open a new path to solve the aggregation of photosensitizers for combating broad-spectrum drug-resistant bacterial infection.

Synthesis of pH-responsive cyclometalated iridium(III) complex and its application in the selective killing of cancerous cells.

Cyclometalated iridium(III) complexes are promising candidates as photosensitizers (PSs) in photodynamic therapy (PDT). The challenge in PDT is the selective killing of cancerous cells over the neighboring normal cells. In this work, a pH-responsive cyclometalated iridium(III) complex (probe 1) was designed and synthesized as an effective PS to selectively kill cancerous cells, with 3-(2-pyridyl)benzaldehyde used as the main ligand and 1-(2-pyridyl)-β-carboline used as an ancillary ligand. Probe 1 shows enhanced photoluminescence emission and higher 1O2 quantum yield in an acidic environment compared to a neutral solution, which led to remarkable phototoxicity toward cancerous cells and high selectivity for killing cancerous cells over normal cells within 10 min. This work demonstrates that the cyclometalated iridium(III) complex with acidic pH-responsive photoluminescence emission and high 1O2 generation is an effective alternative PS for selectively killing cancerous cells.

Experimental and computational studies of novel Sudan-I dye modified conjugated oligomers: Efficient 1O2 generation and antileishmanial characteristics

Introduction of multi-functionality in conducting polymers via modification with dyes is a facile technique that can be adopted to design various kinds of photosensitive and fluorescent polymers. Keeping this in mind, the present work reports for the first time modification of conventional conducting polymers such as polyaniline (PANI) and poly(ophenylenediamine) (POPD) with Sudan-I dye by microwave-assisted method. The chemical structure of prepared oligomers was confirmed by experimental as well as theoretical FT-IR and 1H NMR studies, while the electronic transitions were explored via UV visible analysis. The morphology of the oligomers was confirmed by TEM analysis. The quantum yield (Ф) values were calculated to be 0.40 and 0.54 for SY-PANI and SY-POPD respectively, by fluorescence studies. The oligomers were evaluated for their singlet oxygen (1O2) generation tendency, cytotoxicity and antileishmanial activity. The oligomers were found to effectively generate 1O2 upon excitation under different laser sources. The 1O2 quantum yield and quantum efficiency were found to be 0.13 and 0. 29% under red laser irradiation, while under green laser source, the same values were calculated to be 0.59% and 0.63%. The cytotoxicity analysis revealed that the oligomers were less cytotoxic on human macrophage cell line and significantly inhibited the growth and proliferation of Leishmania parasite – a characteristic which could be exploited for the development of new, effective and least toxic technique to treat leishmaniasis.

Photophysics and drug delivery behavior of methylene blue into Arabic-gum based hydrogel matrices

Methylene blue (MB) is an efficient photosensitizer for Photodynamic Therapy treatment. The photodynamic action is based on the interaction between light with a specific wavelength, a photosensitizer, and oxygen. Reactive oxygen species (ROS), including singlet oxygen (1O2), are created and support the photodynamic action. We verified that the MB presents a high 1O2 quantum yield in distilled water and simulated fluids (simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 6.8)). Hydrogels are investigated for MB delivery to overcome undesirable effects and avoid the formation of non-effective leuco-methylene blue. The glycidyl methacrylate (GMA) was used to modify the Arabic gum structure. pH-responsive hydrogels composed of Arabic gum with different methacrylation degrees (82 and 94 % - MAG82 and MAG94, respectively) are created from the free-radical polymerization mechanism. The low methacrylation degree promotes high MB internalization in the hydrogel. The hydrogels' swelling degree depends on the MB incorporation, methacrylation degree, and pH of the simulated fluid. The MB release in the simulated fluids shows an unusual behavior due to the hydrogel erosion/degradation, attributed to the acid hydrolysis. The amount of released MB in SGF and SIF is similar for the hydrogel containing the high methacrylation degree. On the other hand, the MAG82 hydrogel releases more MB (twice) in SGF than in SIF. The erosion/degradation is more pronounced in the MAGH82 incorporated with the MB (hydrogel MAG82 + MB). Hydrogels matrices containing MB (which acts as photosensitizer) has showed great potential for the treatment of gastrointestinal cancer via Photodynamic Therapy.

Double-Stranded DNA Matrix for Photosensitization Switching

Photosensitization, originated from the activation of triplet states, is the basis of many photodynamic applications, but often competes with a series of nonradiative processes. Herein, we communic...

Photodynamic Activation of Cholecystokinin 1 Receptor with Different Genetically Encoded Protein Photosensitizers and from Varied Subcellular Sites.

Cholecystokinin 1 receptor (CCK1R) is activated by singlet oxygen (1O2) generated in photodynamic action with sulphonated aluminum phthalocyanine (SALPC) or genetically encoded protein photosensitizer (GEPP) KillerRed or mini singlet oxygen generator (miniSOG). A large number of GEPP with varied 1O2 quantum yields have appeared recently; therefore, in the present work, the efficacy of different GEPP to photodynamically activate CCK1R was examined, as monitored by Fura-2 calcium imaging. KillerRed, miniSOG, miniSOG2, singlet oxygen protein photosensitizer (SOPP), flavin-binding fluorescent protein from Methylobacterium radiotolerans with point mutation C71G (Mr4511C71G), and flavin-binding fluorescent protein from Dinoroseobacter shibae (DsFbFP) were expressed at the plasma membrane (PM) in AR4-2J cells, which express endogenous CCK1R. Light irradiation (KillerRed: white light 85.3 mW‧cm−2, 4’ and all others: LED 450 nm, 85 mW·cm−2, 1.5′) of GEPPPM-expressing AR4-2J was found to all trigger persistent calcium oscillations, a hallmark of permanent photodynamic CCK1R activation; DsFbFP was the least effective, due to poor expression. miniSOG was targeted to PM, mitochondria (MT) or lysosomes (LS) in AR4-2J in parallel experiments; LED light irradiation was found to all induce persistent calcium oscillations. In miniSOGPM-AR4-2J cells, light emitting diode (LED) light irradiation-induced calcium oscillations were readily inhibited by CCK1R antagonist devazepide 2 nM; miniSOGMT-AR4-2J cells were less susceptible, but miniSOGLS-AR4-2J cells were not inhibited. In conclusion, different GEPPPM could all photodynamically activate CCK1R. Intracellular GEPP photodynamic action may prove particularly suited to study intracellular GPCR.

Singlet Oxygen Generation via UV-A, -B, and -C Photoexcitation of Isoprene-Oxygen (C5H8-O2) Encounter Complexes in the Gas Phase.

The formation of singlet oxygen 1O2 provided by the photoexcitation of the encounter complexes of isoprene with oxygen (C5H8-O2) in the gas phase within the spectral region 253.5-355 nm has been observed at the elevated pressure of oxygen. Singlet oxygen has been detected with its NIR luminescence centered near 1.27 μm. The photogeneration of 1O2 is found to be a one-photon process. In the UV-C region (253-278 nm) the quantum yield of 1O2 is measured. This yield of 1O2 is governed mainly by photoexcitation of O2 molecules to the Herzberg III (3Δu) state via enhanced absorption by C5H8-O2 collision complexes. So excited triplet O2 gives rise to singlet oxygen because of triplet-triplet annihilation in the collisions with unexcited O2 molecules. In the UV-B (308 nm) region the appearance of 1O2 is attributed to the excitation of a double spin-flip (DSF) transition in complex C5H8-O2. In the UV-A region (355 nm) besides DSF the O2-assisted T1 ← S0 excitation of isoprene to the triplet state takes place, which is a sensitizer of 1O2 formation. The contribution of the encounter complexes C5H8-O2 to the production of singlet oxygen and to the lifetime of isoprene in the Earth's troposphere are estimated.

Effect of UV254 disinfection on the photoformation of reactive species from effluent organic matter of wastewater treatment plant

UV254 is one of the main disinfection methods used in wastewater treatment plants (WWTPs) for the inactivation of pathogens in the effluents before being discharged into the receiving waters. The effluent organic matters (EfOM) are well-known photosensitizers for the generation of reactive species, mainly including the triplet states of EfOM (3EfOM*), singlet oxygen (1O2) and hydroxyl radical (•OH), which contribute to the removal of trace pollutants in water. However, the effect of UV254 disinfection on the photoreactivity of EfOM remains unclear. Here we investigated the photophysical and photochemical properties variation of EfOM after UV254 disinfection, along with humic substances (HS) as comparison. The UV254 disinfection caused a decrease of aromaticity, fluorescence intensity and molecular weight for all samples, while a reduction formation of triplet state of these dissolved organic matters (3DOM*), 1O2, hydrogen peroxide (H2O2), and superoxide anions (O2•−) under simulated sunlight was observed. In contrast, the generation of •OH was increased after UV254 disinfection. The quantum yield of 1O2 was positively correlated with triplet quantum yield coefficient (fTMP) in all cases. However, the quantum yield of •OH exhibited positive and negative correlations with fTMP for EfOM and HS, respectively. The quantum yields showed positive correlations with E2/E3 (ratio of the absorbance at 254 to 365 nm) for untreated DOM samples, while for the first time we found the trends differ distinctly after UV254 disinfection. These findings indicate that UV254 disinfection in WWTPs significantly increases the potential of •OH photoproduction from effluents and the cost-effective solar irradiation after UV254 disinfection is expected to be a novel technique for further removal of pathogen and trace organic pollutants in wastewater effluents and receiving waters.

Near-Infrared Light-Initiated Upconversion Nanoplatform with Tumor Microenvironment Responsiveness for Improved Photodynamic Therapy.

Photodynamic therapy (PDT) is inflowing the mainstream of the cancer treatments, yet the shallow light penetration, thermal damage to normal cells, poor tumor targeting, and skin phototoxicity compromised the PDT efficacy. This paper designed and prepared an upconversion nanoplatform that could effectively convert 808 nm NIR light to red and green light emission, both of which could excite photosensitizers and exert the PDT curative effects. A thin layer of mesoporous silica covering core-shell nanostructure NaGdF4:Yb,Er@NaGdF4:Yb,Nd upconversion nanoparticles was prepared as the carrier to load the photosensitizer pyropheophorbide-a (PPa), which could be excited by green and red light simultaneously and produce high singlet oxygen (1O2) quantum yield (79.1%). Meanwhile, the chemotherapy drug doxorubicin (DOX) was absorbed in the pores of the SiO2 layer to improve the therapeutic effect, and the folic acid-coupled chitosan (Cs-FA) was modified on the surface of the SiO2 layer to obtain the targeting and biocompatible UCNP@SiO2/PPa&DOX@Cs-FA nanoplatform. The physically adsorbed DOX in the pore channel could be released slowly under faintly acidic or GSH stimuli (84% release of DOX after 16 h), suggesting that the nanoplatform was responsive to the tumor microenvironment. In vitro experiments showed that the combined treatment of PDT and DOX was superior to that of PDT alone or DOX chemotherapy alone, implying a synergistic therapeutic effect. The morphological changes and dye staining research of HeLa cells were consistent with the MTT assay. Therefore, this research provided a strategy for the development of an efficient and safe multifunctional cancer treatment nanoplatform integrating low-intensity light excitation, slow release, targeting, photodynamic therapy, and chemotherapy.