Singlet Oxygen Molecules Research Articles

A near-infrared triggered multi-functional indocyanine green nanocomposite with NO gas release function inducing improved photothermal therapy

The integration of photothermal and near-infrared (NIR) imaging capabilities of indocyanine green (ICG) small molecules has attracted considerable attention in tumor diagnosis and treatment. However, the abnormal upregulation of cellular heat shock proteins (HSPs) induced by photothermal therapy (PTT) enhances cellular heat resistance, thereby severely affecting the efficacy of PTT. In this study, to address the impact of HSPs on the efficacy of PTT while obtaining high-quality NIR fluorescence imaging in the NIR region, we designed a targeted peptide@ICG nanofluorescent probe encapsulated in liposomes. The introduced cRGD targeting peptide not only possesses tumor-targeting capabilities but also features LA as the last amino acid in the targeting peptide, which can generate nitric oxide (NO) under reactive oxygen species (ROS) triggering. It can happen under 808 nm single-light source NIR light, and the guanidine group in the peptide decomposes and combines with singlet oxygen molecules to generate NO gas molecules, thereby exerting an elevated photothermal effect by inhibiting the expression of HSP70. In addition, the nanoprobes enable deep imaging and treatment of glioma in situ and can be combined with a laser speckle contrast imaging (LSCI) system for multimodal imaging. This composite probe demonstrates synergistic tumor therapeutic effects of photodynamic therapy (PDT), PTT, and gas therapy, offering a promising strategy for cancer treatment.

Plasmon-enhanced sensitization of singlet oxygen on silver island films

The influence of the plasmonic effect of silver island films on the absorption, fluorescence and long-term luminescence of rose bengal in polyvinyl butyral films has been studied. Under the plasmon effect, the optical density of the dye increased by 3.3 times, the fluorescence intensity by 8.5 times, and the long-lived fluorescence and phosphorescence by 7.08 times and 10.21, respectively. It is shown that in the plasmon field of metal nanoparticles, both an increase in the excitation rate and an increase in the rates of radiative decay of excited singlet and triplet states occur. Phosphorescence of singlet oxygen with a lifetime of 86.46 μs was observed when excited in the absorption band of rose bengal. Based on the calculation of the quenching constants of rose bengal phosphorescence by molecular oxygen molecules, it is shown that the plasmonic effect enhances the energy transfer from dye triplets to oxygen molecules in collision complexes [ТPS…3  g –] as a result of heteroannihilation. Subsequently, the triplet pair decomposes to form a singlet oxygen molecule and a photosensitizer molecule in the ground state. The plasmonic effect of silver nanoparticles leads to an increase in the generation of singlet oxygen by 4.8 times.

Pyrene doped silica nanoparticles: Synthesis, oxygen sensing, and singlet oxygen generation

Dye-doped silica nanoparticles have garnered attention from researchers owing to their beneficial properties, such as signal amplification, surface modification, and biocompatibility. In this study, pyrene-doped silica nanoparticles (PSNPs) were prepared using the reverse microemulsion approach. Pyrenebutyric acid conjugated with aminopropyltriethoxysilane was synthesized to obtain durable PSNPs with low dye leaching via the covalent encapsulation of pyrene inside a silica matrix. The PSNPs were spherical, with a diameter of 72 nm. The PSNPs exhibited excimer fluorescence upon photoexcitation. To demonstrate the applicability of the synthesized PSNPs in biological applications, including photodynamic therapy (PDT) and oxygen sensing, the influence of oxygen on the fluorescence spectrum was investigated. The excimer fluorescence intensity was quenched by oxygen, along with a decrease in fluorescence lifetime. Ratiometric fluorescence sensing and fluorescence lifetime sensing of oxygen concentration were demonstrated. The biomolecular quenching rate constant was evaluated using the Stern–Volmer plot of the fluorescence lifetime. Moreover, utilizing a chemical trap of singlet oxygen molecules, it was demonstrated that singlet oxygen was generated by the photosensitization of PSNP. The PSNPs synthesized in this study are potentially capable of oxygen sensing, PDT, and bioimaging for various biological applications.

Highly efficient photo-degradation for tetracycline elimination in pharmaceutical wastewater by α-Fe2O3/V2O5/BC assisted peroxymonosulfate activation

In this study, a novel α-Fe2O3/V2O5/BC catalyst with highperoxymonosulfate (PMS)activation performance was constructed by co-pyrolysis method and 99.58% of tetracycline is degraded within 120 min. The electrons conversion of Fe-V on biochar surface induces the continuous generation of sulfate radicaland singlet oxygen molecules (1O2).The XPS results show that it is Fe3+and Fe0rather than Fe3+and Fe2+in the iron cycle after the introduction of vanadium, indicating a more efficient electron transfer efficiency between interface. The optical properties characterization and density function theory calculation (DFT) of α-Fe2O3/V2O5/BC reveal that the electrons of the entire α-Fe2O3and the vanadium atoms are redistributed to new molecular orbitals due to strong interfacial chemical bonding, inducing a direct transfer of electrons to generate1O2for tetracycline removal that is the main cause of selective degradation. Besides, the possible degradation mechanism and tetracycline degradation pathways were also proposed. The α-Fe2O3/V2O5/BC maintains a high removal efficiency of tetracycline only decrease by 7.09% after six cycles. This study provides a better strategy and recyclable purification material for the efficient treatment of antibiotic pharmaceutical wastewater.

Photodegradation profiling of nitrendipine: evaluation of active pharmaceutical ingredient, tablets and its altered forms.

Nitrendipine (NTR) is a dihydropyridine drug, which is well-known as a photodegradable pharmaceutical. However, the photochemical reaction of NTR has not been evaluated in detail from now. In this study, we perform the photodegradation profiling of NTR for the elucidation of its photochemical behavior. NTR amounts during ultraviolet light (UV) irradiation were monitored using high performance liquid chromatography (HPLC). NTR was photodegraded almost completely within 24h along with the generation of some photoproducts. Structural determination of two NTR photoproducts were carried out by means of electrospray ionization liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). Obtained results from this study clarified one novel NTR photoproduct, a nitroso pyridine analogue, in addition to a pyridine analogue. Furthermore, photodegradation pathway of NTR was speculated based on chemical structures of NTR photoproducts to clarify its photochemical behavior. It was proposed that a singlet oxygen molecule might withdraw two hydrogen radicals resulting in the form of a pyridine analogue, and the following reduction of its nitro group might produce a nitroso pyridine analogue. Finally, we evaluated the photostability of NTR tablets and its altered forms, indicating that the change of the dosage form led to a decrease of the photostability of NTR tablets. The obtained results will be helpful for the additional research to evaluate the effect of NTR photodegradation on its own biological activities.

Significance of Singlet Oxygen Molecule in Pathologies.

Reactive oxygen species, including singlet oxygen, play an important role in the onset and progression of disease, as well as in aging. Singlet oxygen can be formed non-enzymatically by chemical, photochemical, and electron transfer reactions, or as a byproduct of endogenous enzymatic reactions in phagocytosis during inflammation. The imbalance of antioxidant enzymes and antioxidant networks with the generation of singlet oxygen increases oxidative stress, resulting in the undesirable oxidation and modification of biomolecules, such as proteins, DNA, and lipids. This review describes the molecular mechanisms of singlet oxygen production in vivo and methods for the evaluation of damage induced by singlet oxygen. The involvement of singlet oxygen in the pathogenesis of skin and eye diseases is also discussed from the biomolecular perspective. We also present our findings on lipid oxidation products derived from singlet oxygen-mediated oxidation in glaucoma, early diabetes patients, and a mouse model of bronchial asthma. Even in these diseases, oxidation products due to singlet oxygen have not been measured clinically. This review discusses their potential as biomarkers for diagnosis. Recent developments in singlet oxygen scavengers such as carotenoids, which can be utilized to prevent the onset and progression of disease, are also described.

Coarse-grained description of monounsaturated peroxidized phospholipid bilayers

Lipid peroxides result from a reaction between cis-unsaturated lipid chains and singlet oxygen molecules leading to the addition of a peroxide OOH side group next to the acyl-chain double bond. It is now established that HP-POPC (hydroperoxidized POPC) molecules form stable, thin, and laterally expanded bilayers. The difference in the structural organization arises from the hydrophilic character of the OOH side group that has a strong affinity with the water interface region, leading to significant reorganization of the bilayer. In this article, we describe a coarse-grained (CG) model of POPC and DOPC lipid peroxides within the framework of the Martini CG force-field (v2.2), derived from experimental data. We then discuss extensively the predicted structure and the influence of hydration and show how shifting the position of the unsaturated bonds along the chain changes the structure. Finally, we provide electron and neutron scattering length density profiles of the simulated bilayers.

Alkali metal modified carbon nitride enhance photocatalytic performance for highly selective oxidation of benzyl C(sp3)-H bonds

Photocatalytic selective oxidation of C(sp3)-H bonds is an attractive strategy for synthesis of high value-added products due to the property of solar-driven and mild reaction conditions. However, improving photocatalytic activity and selectivity is still a grand challenge. Herein, we systematically compared the activity and selectivity for photocatalytic oxidation of 4-phenyltoluene by using the as-prepared photocatalysts. The results demonstrated that structure control and alkali metal modification could improve photocatalytic activity and selectivity by increasing the amount of singlet oxygen (1O2) molecules, which was proved by electron paramagnetic resonance (EPR) spectroscopy and phosphorescence (PH) spectroscopy. Moreover, no apparent decrease of conversion rate and selectivity during the 6 cycle runs indicated excellent stability of the prepared photocatalysts. This work revealed a basic mechanism on the energy transfer process of excitons and developed a feasible strategy for the design of C3N4-based photocatalysts.

Novel CaO-SiO2-P2O5 Nanobioglass Activated with Hafnium Phthalocyanine.

Bioactive glasses are materials which can be used in medicine for regeneration of hard and soft tissues. Their functionalization with active molecules or addition to composites broaden significantly the possible range of glass applications. Hereby, we describe photoactive nanoparticles of CaO–SiO2–P2O5 glass modified with dichlorohafnium (IV) phthalocyanine. The low-temperature, sol–gel based reverse micelle method was proposed for the synthesis, which allowed introduction of metal organic molecules into the glass composition. The morphology, structure, and composition of the material was described showing that spherical but agglomerated glass nanoparticles (size below 100 nm) were obtained in the ternary system. It was also shown that optical properties of the phthalocyanine complex were maintained after immobilization of the dye in the glass. The photoluminescence and generation of singlet oxygen molecules were observed under the light irradiation of the glass.

Photodynamic action of photosensitizers based on polycationic derivatives of synthetic bacteriochlorin against human lung cancer cells A549

In view of their potential in the treatment of oncological diseases, photosensitizers (PS) have been the object of active research for the last years. The applied therapeutic photodynamic method involves the activation of a PS by light at a specific wavelength. PS interacts with oxygen and catalyzes the production of singlet oxygen molecules or radical oxygen species which leads to tumor cell death. This work is devoted to the study of the effectiveness of the photodynamic action of new PSs based on polycationic derivatives of synthetic bacteriochlorin on human lung cancer cells A549. The results obtained show that these PS effectively bind to these cells, have high phototoxicity and low ‘dark’ cytotoxicity for them. Morphological and immunohistochemical studies show that photodynamic effect leads to induction of cell necrosis and apoptosis, as well as a sharp decrease in mitotic activity.

Oxidative stress in the skin: Impact and related protection.

Skin, our first interface to the external environment, is subjected to oxidative stress caused by a variety of factors such as solar ultraviolet, infrared and visible light, environmental pollution, including ozone and particulate matters, and psychological stress. Excessive reactive species, including reactive oxygen species and reactive nitrogen species, exacerbate skin pigmentation and aging, which further lead to skin tone unevenness, pigmentary disorder, skin roughness and wrinkles. Besides these, skin microbiota are also a very important factor ensuring the proper functions of skin. While environmental factors such as UV and pollutants impact skin microbiota compositions, skin dysbiosis results in various skin conditions. In this review, we summarize the generation of oxidative stress from exogenous and endogenous sources. We further introduce current knowledge on the possible roles of oxidative stress in skin pigmentation and aging, specifically with emphasis on oxidative stress and skin pigmentation. Meanwhile, we summarize the science and rationale of using three well-known antioxidants, namely vitamin C, resveratrol and ferulic acid, in the treatment of hyperpigmentation. Finally, we discuss the strategy for preventing oxidative stress-induced skin pigmentation and aging.

Three dimensional transient analysis of bubble dynamics in centrifugal bubble singlet oxygen generator for scalable COIL

Chemical Oxygen Iodine Laser (COIL) is the shortest wavelength (1.315 μm) chemical laser employing singlet oxygen molecules as the pumping species and iodine atoms as lasing species. Singlet Oxygen Generator (SOG) is essentially the heart of this laser device which is basically a gas–liquid phase chemical reactor. SOG facilitates the reaction between a basic hydrogen peroxide solution (BHP, H2O2 + KOH) and chlorine gas to produce singlet oxygen molecules. Centrifugal Bubble Single Oxygen Generator (CBSOG) is a potential candidate for an alternative SOG with better operating conditions for high throughput and high power COIL systems. In CBSOG Chlorine gas is bubbled through a layer of BHP solution and the required reaction takes place at the gas–liquid interface of the formed bubbles under high speed rotation of the chamber for gravity independent operation. The performance of this device largely depends on the bubble formation characteristics and their traverse inside the BHP layer. The aim of this paper is to present the numerical analysis of the mechanics of bubble formation, detachment and movement in the BHP layer for different operating parameters as applicable to COIL. The determination of conditions for the transition from bubbling to the jetting regime at different centrifugal accelerations of high magnitude (G ∼ 204 g, 306 g & 387 g) with low liquid column thickness (∼6–8 mm) operating under low pressure (∼100 torr) is another point of focus. The Volume of Fluid (VOF) method has been used for the 3-D transient interface tracking between the phases. This paper also compares the simulation results for various gas flow rates and centrifugal accelerations with select experimental results reported elsewhere showing reasonably good agreement.

Afterglow Amplification for Fast and Sensitive Detection of Porphyria in Whole Blood.

Porphyria is a group of genetic photodermatoses that cause too much porphyrin to accumulate in the blood, skin, and liver, resulting in skin photosensitivity and damage, liver disease, or potential liver failure. Conventional detection methods include high-performance liquid chromatography and fluorescence spectrometry. However, these methods usually require complicated pretreatment and time-consuming processes. Therefore, efficient and fast detection of porphyria is urgently needed. Herein, we develop a molecular afterglow reporter-based sensing scheme for the detection of porphyrins in whole blood. The afterglow reporter can respond to the production of singlet oxygen (1O2) of porphyrins after light excitation, and the detection signals can be amplified through adjusting the amount of singlet oxygen and afterglow reporter molecules. Moreover, without the use of a real-time excitation source, afterglow signals can avoid the scattering and autofluorescence interference in biological samples, thereby reducing background noise. More importantly, we prove the applicability of the afterglow reporter in the quantitative detection of porphyrins in whole blood and demonstrate its great clinical potential.

New Approach in the Application of Conjugated Polymers: The Light-Activated Source of Versatile Singlet Oxygen Molecule.

For many years, the research on conjugated polymers (CPs) has been mainly focused on their application in organic electronics. Recent works, however, show that due to the unique optical and photophysical properties of CPs, such as high absorption in UV–Vis or even near-infrared (NIR) region and efficient intra-/intermolecular energy transfer, which can be relatively easily optimized, CPs can be considered as an effective light-activated source of versatile and highly reactive singlet oxygen for medical or catalytic use. The aim of this short review is to present the novel possibilities that lie dormant in those exceptional polymers with the extended system of π-conjugated bonds.

EVALUATION OF FREE RADICAL SCAVENGING POTENTIAL OF 7-HYDROXY–4-METHYLCOUMARIN ISOLATED FROM MIMOSA NILOTICA (L)

Introduction:Medicinal plants have been used for the treatment of diseases all over the world before the advent of articial clinical drugs and are known to contain substances that can be used for therapeutic uses. Antioxidations act asreducing agents, free radical scavengers, quenchers of singlet oxygen molecule, and activators for antioxidative enzyme to reduce the damage caused by free radicals in biological pattern. Materials and Methods:The isolated organic compound from Mimosa nilotica was subjected to column chromatographic separation and was characterized 1 13 by UV, IR, H-NMR and C-NMR.DPPH assay was conducted to assess the effect of the ethanolic extract and 7-hydroxy–4-methylcoumarin. Result and Discussion:The reports of the in-vitro antioxidation assay indicated that the ethanol extract was more potent than 7-hydroxy–4- methylcoumarin. 7-hydroxy–4-methylcoumarin and ethanolic extractexpress excellent free radical scavenging activity. From the reports it is proved that the reducing power of bioactive constituent is associated with antioxidationpotential. Thus a correlation is proved between reducing power and the antioxidation effect. Conclusion:Previous reports are conrmed that the reducing power of bioactive constituents is associated with antioxidation potential. People who eat various parts of fruits and herbs have a lower risk of heart disease and some neurological diseases and there is evidence that some types of herbs, and fruits in general, protect against some malignant.

Delayed Fluorescence from Carbon Nanotubes through Singlet Oxygen-Sensitized Triplet Excitons

Single-wall carbon nanotubes (SWCNTs) in liquid suspension have been observed to emit delayed, microsecond-scale fluorescence arising from upconverted triplet excitons that are directly created through energy transfer from singlet oxygen molecules (1O2). The singlet oxygen is produced through quenching of an optically excited organic sensitizer. The mechanism of this delayed fluorescence has been deduced from measurements of time-resolved emission kinetics, delayed emission spectra, and polarization-resolved excitation-emission spectra. The observed strong dependence of 1O2 sensitization efficiency on SWCNT structure suggests that (7,6) triplet excitons have an energy near 970 meV. The yields for E11T → E11S upconversion are found to be in the range of several percent. These yields increase with increasing temperature and decrease with increasing excitation intensities, reflecting thermal activation and triplet-triplet exciton annihilation processes.

Molecular interaction and cellular studies on combination photodynamic therapy with rutoside for melanoma A375 cancer cells: an in vitro study

BackgroundMelanoma as a type of skin cancer, is associated with a high mortality rate. Therefore, early diagnosis and efficient surgical treatment of this disease is very important. Photodynamic therapy (PDT) involves the activation of a photosensitizer by light at specific wavelength that interacts with oxygen and creates singlet oxygen molecules or reactive oxygen species (ROS), which can lead to tumor cell death. Furthermore, one of the main approches in the prevention and treatment of various cancers is plant compounds application. Phenolic compounds are essential class of natural antioxidants, which play crucial biological roles such as anticancer effects. It was previously suggested that flavonoid such as rutoside could acts as pro-oxidant or antioxidant. Hence, in this study, we aimed to investigate the effect of rutoside on the combination therapy with methylene blue (MB) assisted by photodynamic treatment (PDT) using red light source (660 nm; power density: 30 mW/cm2) on A375 human melanoma cancer cells.MethodsFor this purpose, the A375 human melanoma cancer cell lines were treated by MB-PDT and rutoside. Clonogenic cell survival, MTT assay, and cell death mechanisms were also determined after performing the treatment. Subsequently, after the rutoside treatment and photodynamic therapy (PDT), cell cycle and intracellular reactive oxygen species (ROS) generation were measured.ResultsThe obtained results showed that, MB-PDT and rutoside had better cytotoxic and antiprolifrative effects on A375 melanoma cancer cells compared to each free drug, whereas the cytotoxic effect on HDF human dermal fibroblast cell was not significant. MB-PDT and rutoside combination induced apoptosis and cell cycle arrest in the human melanoma cancer cell line. Intracellular ROS increased in A375 cancer cell line after the treatment with MB-PDT and rutoside.ConclusionThe results suggest that, MB-PDT and rutoside could be considered as novel approaches as the combination treatment of melanoma cancer.

Ultraefficient Singlet Oxygen Generation from Manganese-Doped Cesium Lead Chloride Perovskite Quantum Dots.

Lead halide perovskites hold promise for photovoltaics, lasers, and light-emitting diode (LED) applications, being known as light-harvesting or -emitting materials. Here we show that colloidal lead halide CsPbCl3 perovskite quantum dots (PQDs), when incorporating divalent manganese (Mn2+) ions, are able to produce spin-paired singlet oxygen molecules with over-unit quantum yield (∼1.08) in air conditions. Our mechanistic studies and atomic-level density functional theory calculations endorse an energy-migration-mediated quantum cutting process favoring multiple singlet oxygen generation (MSOG), in which one exciton-activated bulk Mn2+ ion (∼2.0 eV) inside the nanocrystal migrates its energy among the Mn2+ sublattice to two surface Mn2+ defect states (∼1.0 eV), followed by nonradiative energy transfers to two surrounding oxygen molecules. Moreover, superhydrophobicization of MSOG PQDs through silica-mediated polystyrene encapsulation prevents them from disintegrating in aqueous medium, enabling photodegradation of methyl orange at a rate even higher than that of the canonical titanium oxide photocatalyst. The observation of ultraefficient singlet oxygen generation in PQDs has implications for fields ranging from photodynamic therapy to photocatalytic applications.

1,3-Dipolar cycloaddition reaction of indoles with tosyl azide, subsequent dehydroaromatization and ring-opening cascade: a computational study

The mechanism of the reaction of N-methylindoles with tosyl azide to afford 3-diazoindolin-2-imines and 2-iminoindolines has been studied computationally at the DFT M06/6-311G(d,p) level. The formation of 3-diazoindolin-2-imine is found to proceed via a concerted [3 + 2] addition followed by dehydroaromatization and subsequent ring opening rather than via a concerted [3 + 2] addition followed by ring opening and subsequent dehydroaromatization. The initial [3 + 2] cycloaddition is the rate-determining step with an activation barrier of 17.0 kcal/mol. The formation of 2-iminoindoline is also found to proceed via the initial [3 + 2] cycloaddition followed by a dinitrogen extrusion in a concerted fashion and subsequent 1,2-hydride shift. The rate-determining step for the formation of 2-iminoindoline is either the initial [3 + 2] cycloaddition or the dinitrogen extrusion depending on the nature of indole used. The two competing steps after the initial [3 + 2] cycloaddition are the dehydroaromatization and dinitrogen extrusion step. Dehydroaromatization of dihydrotriazoloindole with singlet oxygen molecule has a barrier of 1.9 kcal/mol and reaction energy of − 54.6 kcal/mol, while with triplet oxygen molecule has high activation barrier of 27.2 kcal/mol and reaction energy of 25.7 kcal/mol leading to the formation of radical intermediates (HOO· + A·). Dehydroaromatization in the absence of oxygen is thermodynamically and kinetically not feasible due to the high activation barrier of 97.5 kcal/mol associated with this process under this condition. Thus, the dehydroaromatization step is predicted to occur with singlet oxygen. Also, dehydroaromatization of dihydrotriazoloindole by singlet oxygen molecule is kinetically and thermodynamically favored over the dinitrogen extrusion by 15.4 kcal/mol and 43.4 kcal/mol, respectively. The low activation barrier of the dehydroaromatization step by singlet oxygen compared to the dinitrogen extrusion step means that 3-diazoindolin-2-imine would be formed solely under this condition, confirming the experimental observation of Sheng et al. (Org Lett 16(4):1244–1247, 2014). In inert atmosphere, 2-iminoindoline becomes viable because the activation barrier for the initial loss of H2 that is likely to lead to the formation of 3-diazoindolin-2-imine is 85.5 kcal/mol higher than the dinitrogen extrusion step for the formation of 2-iminoindoline.

Photochemical upconversion of near-infrared light from below the silicon bandgap

Photochemical upconversion is a strategy for converting infrared light into more energetic, visible light, with potential applications ranging from biological imaging and drug delivery to photovoltaics and photocatalysis. Although systems have been developed for upconverting light from photon energies in the near-infrared, upconversion from below the silicon bandgap has been out of reach. Here, we demonstrate an upconversion composition using PbS semiconductor nanocrystal sensitizers that absorb photons below the bandgap of silicon and populate violanthrone triplet states below the singlet oxygen energy. The triplet-state violanthrone chromophores luminesce in the visible spectrum following energy delivery from two singlet oxygen molecules. By incorporating organic chromophores as ligands onto the PbS nanocrystals to improve energy transfer, we demonstrate that violanthrone upconverts in the absence of oxygen by the triplet–triplet annihilation mechanism. The change in mechanism is shown by exploiting the magnetic field effect on triplet–triplet interactions. Photochemical upconversion of light with photon energy below the silicon bandgap has remained elusive, but the feat has now been demonstrated using PbS semiconductor nanocrystals and violanthrone.