Detection Of Singlet Oxygen Research Articles

Dual-emissive polystyrene@zeolitic imidazolate framework-8 composite for ratiometric detection of singlet oxygen.

This work demonstrated the potential of zeolitic imidazolate framework-8 (ZIF-8) as a host for the co-encapsulation of multiple fluorescent cargos to fabricate fluorescent composites for ratiometric sensing. The one-pot self-assembly of 2-methylimidazole, zinc nitrate, 9-anthracenecarboxylic acid (AnC), and polystyrene sphere doped with europium chelate (EuPS) in methanol solution can lead to the formation of dual-emissive EuPS@AnC/ZIF-8 with excellent fluorescent activity. Based on the distinct fluorescent responses of Eu3+ and AnC to singlet oxygen (1O2), EuPS@AnC/ZIF-8 can be developed as a ratiometric sensor for 1O2 detection. In this ratiometric sensor, Eu3+ fluorescence was employed as a reference signal for providing built-in correction to avoid environmental effects, while AnC fluorescence served as a response signal to detect 1O2 because of its turn-off behavior upon reacting with 1O2. Benefiting from the confinement effect of the ZIF-8 host, the presented sensor showed high sensitivity toward 1O2 with a detection limit of 43 nM and excellent selectivity over other reactive oxygen species. More attractively, the target responsive fluorescent color change of EuPS@AnC/ZIF-8 allowed 1O2 to be easily identified by the naked eye under a UV lamp. We hope that this study will provide a new insight into the design and application of multifunctional composites based on metal-organic frameworks.

Cover Picture: Photosensitized singlet oxygen generation and detection: Recent advances and future perspectives in cancer photodynamic therapy (J. Biophotonics 11–12/2016)

Cover Picture: Photosensitized singlet oxygen generation and detection: Recent advances and future perspectives in cancer photodynamic therapy (J. Biophotonics 11–12/2016)

The hydroxypyridinone iron chelator CP94 increases methyl-aminolevulinate-based photodynamic cell killing by increasing the generation of reactive oxygen species

Methyl-aminolevulinate-based photodynamic therapy (MAL-PDT) is utilised clinically for the treatment of non-melanoma skin cancers and pre-cancers and the hydroxypyridinone iron chelator, CP94, has successfully been demonstrated to increase MAL-PDT efficacy in an initial clinical pilot study. However, the biochemical and photochemical processes leading to CP94-enhanced photodynamic cell death, beyond the well-documented increases in accumulation of the photosensitiser protoporphyrin IX (PpIX), have not yet been fully elucidated. This investigation demonstrated that MAL-based photodynamic cell killing of cultured human squamous carcinoma cells (A431) occurred in a predominantly necrotic manner following the generation of singlet oxygen and ROS. Augmenting MAL-based photodynamic cell killing with CP94 co-treatment resulted in increased PpIX accumulation, MitoSOX-detectable ROS generation (probably of mitochondrial origin) and necrotic cell death, but did not affect singlet oxygen generation. We also report (to our knowledge, for the first time) the detection of intracellular PpIX-generated singlet oxygen in whole cells via electron paramagnetic resonance spectroscopy in conjunction with a spin trap.

Anthracene-based fluorescent nanoprobes for singlet oxygen detection in biological media

We have developed a novel singlet oxygen nanoprobe based on 9,10-anthracenedipropionic acid covalently bound to mesoporous silica nanoparticles. The nanoparticle protects the probe from interactions with proteins, which detract from its ability to detect singlet oxygen. In vitro studies show that the nanoprobe is internalized by cells and is distributed throughout the cytoplasm, thus being capable of detecting intracellularly-generated singlet oxygen.

WE-FG-BRA-12: Research Work of the Radio-Dynamic Treatment Mechanism

Purpose: The finite penetration depth of Laser light has limited clinical applications for PDT. This present work investigates the activation of photosensitizers using Cerenkov light emission from 45MV photon beams produced in an LA45 cancer therapy accelerator. We have named this new treatment technique Radio-Dynamic Therapy (RDT). Methods: Monte Carlo simulations were made on various Cerenkov emission energies and their spectroscopy in excited target areas in order to estimate their photosensitizer inner activation efficiency. The Cerenkov light excitation efficiency used in RDT has been theoretically compared with the exotic excitation efficiency of external Laser light used in PDT. In addition, laboratory tests showed the differences of the excitation efficiencies between a patented catalyst coenzyme added as a substrate, and then without the coenzyme. A specific probe of DMA (Singlet Oxygen fluorescent probe-9, 10-dimethylanthracene) was also used to detect singlet oxygen. Finally, we also compared our results with similar previous experimental work reported in the scientific literature. Results: Our Monte Carlo results showed that the Cerenkov light intensity induced with 45MV beams from an LA45 is 8 – 10 times the Cerenkov light intensity induced with 6MV beams from conventional accelerators. Furthermore, the patented catalyst coenzyme enhanced the excitation efficiency of photosensitizers by 3–6 times under different conditions. In clinical situations, the new RDT technique also showed favorable outcomes for early and late stages of specific cancers and it is also good at metastatic cancer treatment. Conclusion: Our results indicated that the process of using the Cerenkov light emission to excite photosensitizers from 45MV photons has a similar process and efficiency as the conventional laser in PDT. Comparing the advantages of RDT with a conventional PDT, the RDT may be developed into a potential treatment modality for a wider range of cancers stages as well as for other diseases.

Photosensitized singlet oxygen generation and detection: Recent advances and future perspectives in cancer photodynamic therapy.

Photodynamic therapy (PDT) uses photosensitizers and visible light in combination with molecular oxygen to produce reactive oxygen species (ROS) that kill malignant cells by apoptosis and/or necrosis, shut down the tumor microvasculature and stimulate the host immune system. The excited singlet state of oxygen (1 O2 ) is recognized to be the main cytotoxic ROS generated during PDT for the majority of photosensitizers used clinically and for many investigational new agents, so that maximizing its production within tumor cells and tissues can improve the therapeutic response, and several emerging and novel approaches for this are summarized. Quantitative techniques for 1 O2 production measurement during photosensitization are also of immense importance of value for both preclinical research and future clinical practice. In this review, emerging strategies for enhanced photosensitized 1 O2 generation are introduced, while recent advances in direct detection and imaging of 1 O2 luminescence are summarized. In addition, the correlation between cumulative 1 O2 luminescence and PDT efficiency will be highlighted. Meanwhile, the validation of 1 O2 luminescence dosimetry for PDT application is also considered. This review concludes with a discussion on future demands of 1 O2 luminescence detection for PDT dosimetry, with particular emphasis on clinical translation. Eye-catching color image for graphical abstract.

Improved synthesis dimethylhomoecoerdianthrone (HOCD) and its functionalization through facile amination reactions

An improved synthesis of dimethylhomoecoerdianthrone (HOCD), a dye used for singlet oxygen detection, was reported by isolation of a key intermediate followed by cyclization reaction. Moreover, dehydrogenative amination reaction between HOCD and alkyl amines and diamines resulted in amine functionalized HOCD derivatives with good yield. The observed reactivity depends on the nucleophilicity of amine and electrophilicity of HOCD. DFT calculations suggest that the reaction involves 1,4-Michael addition followed by migration of hydrogen atom due to aromatization. Under the aerated conditions, dehydrogenation occurs to restore the ketone structure. This C-N coupling reaction can be utilized to construct molecular materials with near infrared photonic properties. Finally, we illustrated that the HOCD derives, HOCD-SO3−, can be grafted to semiconductor nanocrystals (quantum dots) to give turn-on fluorescent nanoprobe for highly selective detection of singlet oxygen.

Direct measurement of singlet oxygen by using a photomultiplier tube-based detection system

The effective dosimetry for photodynamic therapy (PDT) can be specified by direct measurement of singlet oxygen (1O2) production. The purpose of this study was to investigate the feasibility of a newly developed photomultiplier tube (PMT)-based singlet oxygen detection (SOD) system. The lowest and highest 1O2 concentrations detectable by the PMT-SOD system were 15nM and 10μM, respectively. Dose-dependent quenching, by NaN3, of the fluorogenic reaction was observed, which was negatively correlated with the 1O2 level measured by the PMT-SOD system. The lifetime of 1O2, as measured by the PMT-SOD system, was found to be lengthened when H2O was replaced with deuterium oxide. 1O2 photon counts were significantly and dose-dependently correlated with intracellular fluorescence intensity after photosensitizer treatments. In vitro cell viability test and in vivo xenografted-tumor mass shrinkage showed a positive association between PDT-induced cytotoxicity and 1O2 production concomitantly measured by the PMT-SOD system. It was concluded that the PMT-SOD system is capable of measuring 1O2 production directly and accurately, demonstrating that this system can be useful in the determination of dosimetry for PDT.

A Classic Near-Infrared Probe Indocyanine Green for Detecting Singlet Oxygen.

The revelation of mechanisms of photodynamic therapy (PDT) at the cellular level as well as singlet oxygen (1O2) as a second messengers requires the quantification of intracellular 1O2. To detect singlet oxygen, directly measuring the phosphorescence emitted from 1O2 at 1270 nm is simple but limited for the low quantum yield and intrinsic efficiency of 1O2 emission. Another method is chemically trapping 1O2 and measuring fluorescence, absorption and Electron Spin Resonance (ESR). In this paper, we used indocyanine green (ICG), the only near-infrared (NIR) probe approved by the Food and Drug Administration (FDA), to detect 1O2 in vitro. Once it reacts with 1O2, ICG is decomposed and its UV absorption at 780 nm decreases with the laser irradiation. Our data demonstrated that ICG could be more sensitive and accurate than Singlet Oxygen Sensor Green reagent® (SOSG, a commercialized fluorescence probe) in vitro, moreover, ICG functioned with Eosin Y while SOSG failed. Thus, ICG would reasonably provide the possibility to sense 1O2 in vitro, with high sensitivity, selectivity and suitability to most photosensitizers.

Ultrasensitive Time- and Space-Resolved Detection of Luminescene, I.E. Singlet Oxygen Phosphorescence

Biology, medicine, and material science, especially many kinds of solar cell research and production demand for time- and spatially resolved detection in the near infrared spectral region. Observation of singlet oxygen phosphorescence is, for example, important for understanding cell-cell interactions and in the field of photo-dynamic therapy. Whereas the temporal behavior of the luminescence from semiconductors is an agreed indicator for the quality of wafer material.Single photon counting based data acquisition has proven to yield the best sensitivity and a very high dynamic range - it is therefore the ideal method for measuring weak luminescence in the near infrared spectral region. Based on this principle, we present the methodology for state-of-the-art luminescence measurements. Our hardware is designed to detect spectrally- and spatially-resolved weak emission in steady-state and time-resolved manner. Depending on the samples size and aggregation state, large excitation volume spectrometer or diffraction limited small excitation spot microscope systems are employed. A combination of both types of set-ups allows us to record even spectrally-resolved images. The high sensitivity of these systems was proven by detecting singlet oxygen phosphorescence from aqueous samples of photo-sensitizers. With the reached detection sensitivity level it is feasible to record even singlet oxygen phosphorescence images.

Molecular dyad approaches to the detection and photosensitization of singlet oxygen for biological applications.

The principles and prospects of a molecular dyad strategy for photocontrolling biological singlet oxygen are highlighted.

Time-resolved singlet-oxygen luminescence detection with an efficient and practical semiconductor single-photon detector.

In clinical applications, such as PhotoDynamic Therapy, direct singlet-oxygen detection through its luminescence in the near-infrared range (1270 nm) has been a challenging task due to its low emission probability and the lack of suitable single-photon detectors. Here, we propose a practical setup based on a negative-feedback avalanche diode detector that is a viable alternative to the current state-of-the art for different clinical scenarios, especially where geometric collection efficiency is limited (e.g. fiber-based systems, confocal microscopy, scanning systems etc.). The proposed setup is characterized with Rose Bengal as a standard photosensitizer and it is used to measure the singlet-oxygen quantum yield of a new set of photosensitizers for site-selective photodynamic therapy.

Ligand Based Dual Fluorescence and Phosphorescence Emission from BODIPY Platinum Complexes and Its Application to Ratiometric Singlet Oxygen Detection.

Four new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacen-8-yl (BODIPY) platinum(II) complexes of the type cis-/trans-Pt(BODIPY)Br(PR3)2 (R = Et or Ph) were synthesized and characterized by NMR, electronic absorption, and luminescence spectroscopy. Three of the complexes were also studied by single crystal X-ray diffraction. The absorption profiles of the four complexes feature intense HOMO → LUMO π → π* transitions with molar extinction coefficients ε of ca. 50 000 M(-1)cm(-1) at around 475 nm and vibrational progressions that are characteristic of BODIPYs. Most remarkably, most complexes exhibit dual emissions through fluorescence at ca. 490 nm and phosphorescence at ca. 650 nm that originate from Pt-perturbed BODIPY-centered (1)ππ* or (3)ππ* states, respectively. Electronic absorption and luminescence spectroscopy data are in good agreement with our TD-DFT calculations. While the emission of the cis-complexes is dominated by fluorescence, their trans-isomers emit predominantly through phosphorescence with a phosphorescence quantum yield for trans-Pt(BODIPY)Br(PEt3)2 (trans-1) of 31.2%. trans-1 allows for ratiometric one-component oxygen sensing in fluid solution up to atmospheric concentration levels and exhibits a remarkably high Stern-Volmer constant for the quenching of the excited triplet state by oxygen of ca. 350 bar(-1) as determined by changes in phosphorescence intensity and lifetime.

Fluorophore, Protoporphyrin IX (PpIX), Excited From Cerenkov Emission Produced by 45MV Radiation for Cancer Therapy

Fluorophore, Protoporphyrin IX (PpIX), Excited From Cerenkov Emission Produced by 45MV Radiation for Cancer Therapy

Phenothiazines grafted on the electrode surface from diazonium salts as molecular layers for photochemical generation of singlet oxygen

Four amine-derivative phenothiazines were converted to the corresponding diazonium salt forms prior to their electrochemical grafting on the GC electrode with the aim to assess their ability to generate singlet oxygen. It was demonstrated by cyclic voltammetry and XPS spectroscopy that the molecular layers were effectively bound to the GC surface by applying the reductive potential in situ in the reaction diazo-mixture. The chosen procedure without the product separation step, appears to be especially useful due to the high solubility of the resulted phenothiazine diazonium salts. The effectiveness of singlet oxygen generation was measured for all of the grafted surfaces by UVVis spectra monitoring of the adjacent solution phase of 1,3-diphenylisobenzofuran (DPBF), which is well known trapping molecule used in detection of singlet oxygen. The data presented in the work prove that all of the molecular layers are effective singlet oxygen generators that might be used for various areas of applications where a highly oxidative reactant is required.

Enhanced efficacy of photodynamic therapy by inhibiting ABCG2 in colon cancers.

BackgroundPhotodynamic therapy (PDT) contains a photosensitizing process, which includes cellular uptake of photosensitizer and delivery of light to the target. ATP-binding cassette subfamily G2 (ABCG2) regulates endogenous protoporphyrin levels. In human colon cancers, it is not fully examined the role of ABCG2 in porphyrin-based photodynamic therapy.MethodsSW480 and HT29 cells were selected because they showed low and high ABCG2 expression levels, respectively. Pyropheophorbid-a (PPa) was used as a photosensitizer. Cells were exposed to a 670 nm diod laser. Cell viability and necrosi apoptosis was examined. Production level of singlet oxygen was detected with the photomultiplier-tube s/ -based singlet oxygen detection system.ResultsSW480 cells, which expressed lower level of ABCG2, showed the higher uptake of PPa than HT-29 cells. The uptake level of PPa was significantly correlated with the decreased cell viability after PDT. Pretreatment with a ABCG2 inhibitor, Ko-143, significantly enhanced the PDT efficacy in HT29 cells compared to vehicle-pretreated cells. To confirm the ABCG2 effect on PDT, we established ABCG2 over-expressing stable cells in SW480 cells (SW480/ABCG2). Furthermore, SW480/ABCG2 cells showed significantly decreased PDT effect compared to the control cells. The increased or decreased cell survival was significantly correlated with the production level of singlet oxygen after PDT.ConclusionABCG2 plays an important role in determining the PDT efficacy by controlling the photosensitizer efflux rate. This implies the control of ABCG2 expression may be a potential solution to enhance photosensitivity.

Tu1949 Escaping of ATP-Binding Cassette Sub Family G Member 2 by Pegylated-Photosensitizer Increases the Efficacy of Photodynamic Therapy in Pancreatic Cancer

Purpose : Porphyrin-based photosensitizers are most commonly used in photodynamic therapy (PDT). However, these drugs are exported extracellularly by a cell-mambrane transporter, the ATP-binding cassette subfamily G member 2 (ABCG2), which decreases the PDTinduced cytotoxicity in cancer treatment. Pegylation of a drug increases its molecular size. We hypothesized that intracellular level of a porphyrin can be increased by its pegylated form, which enhance the PDT-induced cytotoxicity. Our aim of study was to examine the escaping of ABCG2 function in the PDT using pegylated-Chlorin E6 (Che6) in the pancreatic cancer cells. Methods : We pegylated Che6 using a methoxy polyethylene glycol and branched polyethylenimine. AsPC-1 and MiaPaCa-2 cells were selected, which showed the low and high ABCG2 expression level, respectively. Intracellular level of Che6 and pegylatedChe6 was detected by Fluorescence meter, FACS and confocal microscope. Cells were incubated with 0.1 10 μM of Che6 and pegylated-Che6. They were exposed to a diode laser emitting at 670 nm wave length with total radiation dose of 6 J/cm2. Cell viability was determined by MTT assay. Production level of singlet oxygen was detected with photomultiplier-tube based singlet oxygen detection system. An antitumor PDT effects in AsPC-1 cellbearing BALC/nude mice of the Che6 and pegylated-Che6 were investigated. Results : The

Tu1950 Psychological Distress and Its Impact on the Survival in Patients With Pancreatic Cancer: A Prospective Analysis

Purpose : Porphyrin-based photosensitizers are most commonly used in photodynamic therapy (PDT). However, these drugs are exported extracellularly by a cell-mambrane transporter, the ATP-binding cassette subfamily G member 2 (ABCG2), which decreases the PDTinduced cytotoxicity in cancer treatment. Pegylation of a drug increases its molecular size. We hypothesized that intracellular level of a porphyrin can be increased by its pegylated form, which enhance the PDT-induced cytotoxicity. Our aim of study was to examine the escaping of ABCG2 function in the PDT using pegylated-Chlorin E6 (Che6) in the pancreatic cancer cells. Methods : We pegylated Che6 using a methoxy polyethylene glycol and branched polyethylenimine. AsPC-1 and MiaPaCa-2 cells were selected, which showed the low and high ABCG2 expression level, respectively. Intracellular level of Che6 and pegylatedChe6 was detected by Fluorescence meter, FACS and confocal microscope. Cells were incubated with 0.1 10 μM of Che6 and pegylated-Che6. They were exposed to a diode laser emitting at 670 nm wave length with total radiation dose of 6 J/cm2. Cell viability was determined by MTT assay. Production level of singlet oxygen was detected with photomultiplier-tube based singlet oxygen detection system. An antitumor PDT effects in AsPC-1 cellbearing BALC/nude mice of the Che6 and pegylated-Che6 were investigated. Results : The

Photo-oxidation of ergosterol: Indirect detection of antioxidants photosensitizers or quenchers of singlet oxygen

Consumption of antioxidant supplements is associated to prevention of several diseases. However, recent studies suggest that antioxidants, besides scavenge free radicals could lead development of tumors. Due to conflicting reports on the antioxidant benefits, the capacity to photosensitize the generation of singlet oxygen of seven natural antioxidants was evaluated through photo-oxidation of ergosterol which proved to be an efficient method of indirect detection of singlet oxygen. Our results showed that curcumin, resveratrol and quercetin have pro-oxidant activity due they act as photosensitizers in generation of singlet oxygen. In addition, we observed that genistein, naringenin, β-carotene and gallic acid besides their antioxidant activity against ROS radicals, are capable of quenching ROS non-radicals as singlet oxygen. Finally, our results allow us to propose a new approach in classification of natural antioxidants scavengers of free radicals, based on their activity as quenchers of singlet oxygen or as photosensitizers in singlet oxygen generation.

Methods for the detection and determination of singlet oxygen

Methods for the detection of singlet oxygen in gaseous and liquid media are considered. Their advantages and shortcomings are discussed, including those in the quantitative determination of singlet oxygen.