Fiber-optic singlet oxygen [1O2 (1Delta(g))] generator device serving as a point selective sterilizer

Advancements in photodynamic therapy of esophageal cancer

The poor prognosis of patients with esophageal cancer leads to the constant search for new ways of treatment of this disease. One of the methods used in high-grade dysplasia, superficial invasive carcinoma, and sometimes palliative care is photodynamic therapy (PDT). This method has come a long way from the first experimental studies to registration in the treatment of esophageal cancer and is constantly being improved and refined. This review describes esophageal cancer, current treatment methods, the introduction to PDT, the photosensitizers (PSs) used in esophageal carcinoma PDT, PDT in squamous cell carcinoma (SCC) of the esophagus, and PDT in invasive adenocarcinoma of the esophagus. For this review, research and review articles from PubMed and Web of Science databases were used. The keywords used were "photodynamic therapy in esophageal cancer" in the years 2000-2020. The total number of papers returned was 1,000. After the review was divided into topic blocks and the searched publications were analyzed, 117 articles were selected.

Photodynamic Therapy-Adjunctive Therapy in the Treatment of Prostate Cancer

The alarming increase in the number of advanced-stage prostate cancer cases with poor prognosis has led to a search for innovative methods of treatment. In response to the need for implementation of new and innovative methods of cancer tissue therapy, we studied photodynamic action in excised prostate tissue in vitro as a model for photodynamic therapy. To ascertain the effects of photodynamic action in prostate tissue, Rose Bengal (0.01 to 0.05 mM) was used as a photosensitizer in the presence of oxygen and light to generate singlet oxygen in tissues in vitro. Five preset concentrations of Rose Bengal were chosen and injected into prostate tissue samples (60 samples with 12 replications for each RB concentration) that were subsequently exposed to 532 nm light. The effects of irradiation of the Rose Bengal infused tissue samples were determined by histopathological analysis. Histopathological examination of prostate samples subjected to photodynamic action revealed numerous changes in the morphology of the neoplastic cells and the surrounding tissues. We conclude that the morphological changes observed in the prostate cancer tissues were a result of the photogeneration of cytotoxic singlet oxygen. The tissue damage observed post photodynamic action offers an incentive for continued in vitro investigations and future in vivo clinical trials.

Interparticle Delivery and Detection of Volatile Singlet Oxygen at Air/Solid Interfaces

An interparticle system has been devised, allowing airborne singlet oxygen to transfer between particle surfaces. Singlet oxygen is photogenerated on a sensitizer particle, where it then travels through air to a second particle bearing an oxidizable compound-a particulate-based approach with some similarities to reactive oxygen quenching in the atmosphere. In atmospheric photochemistry, singlet oxygen is generated by natural particulate matter, but its formation and quenching between particles has until now not been determined. Determining how singlet oxygen reacts on a second surface is useful and was developed by a three-phase system (particle-air-particle) interparticulate photoreaction with tunable quenching properties. We identify singlet oxygen quenching directly by near-IR phosphorescence in the airborne state and at the air/particle interface for total quenching rate constants (k_T) of adsorbed anthracene trapping agents. The air/solid interface k_T of singlet oxygen by anthracene-coated particles was (2.8 ± 0.8) × 10⁷ g mol^-1 s^-1 for 9,10-dimethylanthracene and (2.1 ± 0.9) × 10⁷ g mol^-1 s^-1 for 9,10-anthracene dipropionate dianion, and the lifetime of airborne singlet oxygen was measured to be 550 μs. These real-time interactions and particle-induced quenching steps open up new opportunities for singlet oxygen research of atmospheric and particulate processes.

Alternative methods of photodynamic therapy and oxygen consumption measurements-A review

Photooxidation generates reactive oxygen species (ROS) through the interaction of dyes or surfaces with light radiation of appropriate wavelength. The reaction is of wide utility and is highly effective in photodynamic therapy (PDT) of various types of cancer and skin disease. Understanding generation of singlet oxygen has contributed to the development of PDT and its subsequent use in vivo. However, this therapy has some limitations that prevent its use in the treatment of cancers located deep within the body. The limited depth of light penetration through biological tissue limits initiation of PDT action in deep tissue. Measurement of oxygen photo consumption is critical due to tumor hypoxia, and use of magnetic resonance imaging (MRI) is particularly attractive since it is non-invasive. This article presents bioluminescence (BL) and chemiluminescence (CL) phenomena based on publications from the last 20 years, and preliminary results from our lab in the use of MRI to measure oxygen concentration in water. Current work is aimed at improving the effectiveness of singlet oxygen delivery to deep tissue cancer.

A simple, inexpensive method for gas-phase singlet oxygen generation from sensitizer-impregnated filters: Potential application to bacteria/virus inactivation and pollutant degradation

Airborne infectious diseases such as the new Coronavirus 2019 (COVID-19) pose serious threat to human health. Indoor air pollution is a problem of global environmental concern as well. Singlet oxygen (¹O₂) is a reactive oxygen species that plays important role in bacteria/virus inactivation and pollutant degradation. In this study, we found that commercially available filters typically deployed in air purifier and air conditioning units, when impregnated with Rose Bengal (RB) as a ¹O₂ sensitizer, can be used for heterogeneous gas-phase generation of ¹O₂. It was confirmed that irradiation of the RB filter under oxygen gas stream produced ¹O₂, which was measured using furfuryl alcohol trapping method followed by HPLC analysis. It was also observed that the amount of ¹O₂ generated increases as the light intensity increased. Similarly, the sensitizer loading also positively influenced the ¹O₂ generation. The heterogeneous gas-phase generation of ¹O₂ can find potential applications in air purifier and air conditioning units for the purpose of bacteria/virus inactivation and/or pollutant degradation thereby improving indoor air quality.

Synthesis and Characterization of Ru(II) Complexes with π-Expansive Imidazophen Ligands for the Photokilling of Human Melanoma Cells

Ru(II) complexes were synthesized with π-expanding (phenyl, fluorenyl, phenanthrenyl, naphthalen-1-yl, naphthalene-2-yl, anthryl and pyrenyl groups) attached at a 1H-imidazo[4,5-f][1,10]phenanthroline ligand and 4,4'-dimethyl-2,2'-bipyridine (4,4'-dmb) coligands. These Ru(II) complexes were characterized by 1D and 2D NMR, and mass spectroscopy, and studied for visible light and dark toxicity to human malignant melanoma SK-MEL-28 cells. In the SK-MEL-28 cells, the Ru(II) complexes are highly phototoxic (EC₅₀  = 0.2-0.5 µm) and have low dark toxicity (EC₅₀  = 58-230 µm). The highest phototherapeutic index (PI) of the series was found with the Ru(II) complex bearing the 2-(pyren-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline ligand. This high PI is in part attributed to the π-rich character added by the pyrenyl group, and a possible low-lying and longer-lived ³ IL state due to equilibration with the ³ MLCT state. While this pyrenyl Ru(II) complex possessed a relatively high quantum yield for singlet oxygen formation (Φ_∆  = 0.84), contributions from type-I processes (oxygen radicals and radical ions) are competitive with the type-II (¹ O₂ ) process based on effects of added sodium azide and solvent deuteration.

Effect of Toxic Metal Ions on Photosensitized Singlet Oxygen Generation for Photodegradation of Polyaromatic Hydrocarbon Derivatives and Inactivation of Escherichia coli

Here, we report an experimental study of the effect of toxic metal ions on photosensitized singlet oxygen generation for photodegradation of PAH derivatives, Anthracene-9,10-dipropionic acid disodium salt (ADPA) and 1,5-dihydroxynapthalene (DHN) and photoinactivation of Escherichia coli bacteria by using cationic meso-tetra(N-methyl-4-pyridyl)porphine tetrachloride (TMPyP) as a singlet oxygen photosensitizer. Three s-block metals ions, such as Na⁺ , K⁺ and Ca²⁺ and five toxic metals such as Cd²⁺ , Cu²⁺ , Hg²⁺ , Zn²⁺ and Pb²⁺ were studied. The s-block metal ions showed no change in the rate of photodegradation of ADPA or DHN by TMPyP, whereas a dramatic change in the photodegradation of ADPA and DHN was observed in the presence of toxic metals. The maximum photodegradation rate constants of ADPA and DHN were observed for Cd²⁺ ions [(3.91 ± 0.20) × 10^-3 s^-1 and (7.18 ± 0.35) × 10^-4 s^-1 , respectively]. Strikingly, the photodegradation of ADPA and DHN was almost completely inhibited in the presence of Hg²⁺ ions and Cu²⁺ ions. A complete inhibition of growth of E. coli was observed upon visible light irradiation of E. coli solutions with TMPyP and toxic metal ions particularly, Cd²⁺ , Hg²⁺ , Zn²⁺ and Pb²⁺ ions, except for Cu²⁺ ions where a significantly slow inhibition of E. coli's growth was observed.

Transparent organosilica photocatalysts activated by visible light: photophysical and oxidative properties at the gas-solid interface

The photophysical properties of several photosensitizers (PSs) included or grafted in silica monoliths were compared to their properties in solution. The effects of the solid support on their steady-state and transient absorption spectra, on their quantum yields of singlet oxygen ((1)O2) production, and on their ability to photoinduce the oxidation of dimethylsulfide (DMS) were investigated. Two cyanoanthracene derivatives (9,14-dicyanobenzo[b]triphenylene, DBTP, and 9,10-dicyanoanthracene, DCA), as well as three phenothiazine dyes (methylene blue, MB(+), new methylene blue, NMB(+), methylene violet, MV), were encapsulated in silica, analyzed and compared to two reference PSs (perinaphthenone, PN and rose bengal, RB). A DBTP derivative (3-[N-(N″-triethoxysilylpropyl-N'-hexylurea)]carboxamido-9,14-dicyanobenzo[b]triphenylene, 3) was also prepared and grafted onto silica. Thanks to the transparency and the free-standing shape of the monoliths, the complete spectroscopic characterization of the supported PSs was carried out directly at the gas-solid interface. The influence of the silica network, the PS, and the adsorption/grafting link between the PS and silica was investigated. The effects of PS concentration, gaseous atmosphere, humidity, and hydrophobicity on the production of (1)O2 were analyzed. With all PSs, (1)O2 production was very efficient (quantum yields of (1)O2 production, relative to PN, between 0.6 and 1), and this species was the only one involved in the pollutant photooxidation. The influence of the matrix on the PSs' photophysics could be considered as negligible. In contrast, the matrix effect on DMS photooxidation was extremely important: the gas diffusion inside the porous structure, and thus, the photoactivity of the materials, strictly depended on silica's surface area and porosity. Our results highlight the suitability of these silica structures as inert supports for the study of the photosensitizing properties at the gas-solid interface. Moreover, thanks to the adsorption properties of the matrix, the synthesized materials can be used as microphotoreactor for the (1)O2-mediated oxidation of volatile pollutants.

A fiberoptic (photodynamic therapy type) device with a photosensitizer and singlet oxygen delivery probe tip for ovarian cancer cell killing

A portable "fiber optic-based sensitizer delivery" (FOSD) device has been developed and studied. Before there might be success in photodynamic therapy (PDT) and antibacterial ambitions, an understanding of basic factors on device performance was needed. Thus, the device was examined for the localized delivery of sensitizer molecules in ovarian cancer cells and production of high concentrations of singlet oxygen for their eradication in vitro. The device tip releases stored pheophorbide by attack of singlet oxygen from sensitized oxygen gas delivered through the hollow fiber using 669 nm laser light. The performance of the device was enhanced when configured with a fluorosilane tip by virtue of its Teflon-like property compared with a conventional glass tip (greater sensitizer quantities were photoreleased and laterally diffused, and greater amounts of ovarian OVCAR-5 cancer cells were killed). No cell damage was observed at 2.2 N of force applied by the probe tip itself, an amount used for many of the experiments described here.

Bacterial inactivation by a singlet oxygen bubbler: identifying factors controlling the toxicity of (1)O2 bubbles

A microphotoreactor device was developed to generate bubbles (1.4 mm diameter, 90 μL) containing singlet oxygen at levels toxic to bacteria and fungus. As singlet oxygen decays rapidly to triplet oxygen, the bubbles leave behind no waste or byproducts other than O(2). From a comparative study in deaerated, air saturated, and oxygenated solutions, it was reasoned that the singlet oxygen bubbles inactivate Escherichia coli and Aspergillus fumigatus, mainly by an oxygen gradient inside and outside of the bubble such that singlet oxygen is solvated and diffuses through the aqueous solution until it reacts with the target organism. Thus, singlet oxygen bubble toxicity was inversely proportional to the amount of dissolved oxygen in solution. In a second mechanism, singlet oxygen interacts directly with E. coli that accumulate at the gas-liquid interface although this mechanism operates at a rate approximately 10 times slower. Due to encapsulation in the gaseous core of the bubble and a 0.98 ms lifetime, the bubbles can traverse relatively long 0.39 mm distances carrying (1)O(2) far into the solution; by comparison the diffusion distance of (1)O(2) fully solvated in H(2)O is much shorter (~150 nm). Bubbles that reached the outer air-water interface contained no (1)O(2). The mechanism by which (1)O(2) deactivated organisms was explored through the addition of detergent molecules and Ca(2+) ions. Results indicate that the preferential accumulation of E. coli at the air-water interface of the bubble leads to enhanced toxicity of bubbles containing (1)O(2). The singlet oxygen device offers intriguing possibilities for creating new types of disinfection strategies based on photodynamic ((1)O(2)) bubble carriers.

Generating singlet oxygen bubbles: a new mechanism for gas-liquid oxidations in water

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [(1)O(2) ((1)Δ(g))] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiberoptic receptacles loaded with 150 μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O(2) gas to the reactor chambers. In the presence of O(2), singlet oxygen was generated by illuminating the sensitizer particles with 669 nm light from an optical fiber coupled to the top of the reactor. The generated (1)O(2) was transported through the membrane by the O(2) stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, or N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that (1)O(2) transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow; it arose only from (1)O(2)-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves (1)O(2) mass transfer and solvation, where smaller bubbles provide better penetration of (1)O(2) into the flowing stream due to higher surface-to-volume contact between the probe molecules and (1)O(2).

Photosensitization reactions in vitro and in vivo

This review of Photochemistry and Photobiology summarizes articles published in 2010, and highlights progress in the area of photosensitization. The synthesis of conjugated photosensitizers is an area of interest where increasing water solubility has been a goal. Targeting infrared sensitizer absorption has been another goal, and relates to the practical need of deep tissue absorption of light. Photodynamic techniques for inactivating microbes and destroying tumors have been particularly successful. Biologically, singlet oxygen [(1)O(2)((1)Δ(g))] is an integral species in many of these reactions, although photosensitized oxidations tuned to electron and hydrogen transfer (Type I) give rise to other reactive species, such as superoxide and hydrogen peroxide. How photoprotection against yellowing, oxygenation and degradation occurs was also an area of topical interest.

Photosensitizer drug delivery via an optical fiber

An optical fiber has been developed with a maneuverable mini-probe tip that sparges O(2) gas and photodetaches pheophorbide (sensitizer) molecules. Singlet oxygen is produced at the probe tip surface which reacts with an alkene spacer group releasing sensitizer upon fragmentation of a dioxetane intermediate. Optimal sensitizer photorelease occurred when the probe tip was loaded with 60 nmol sensitizer, where crowding of the pheophorbide molecules and self-quenching were kept to a minimum. The fiber optic tip delivered pheophorbide molecules and singlet oxygen to discrete locations. The 60 nmol sensitizer was delivered into petrolatum; however, sensitizer release was less efficient in toluene-d(8) (3.6 nmol) where most had remained adsorbed on the probe tip, even after the covalent alkene spacer bond had been broken. The results open the door to a new area of fiber optic-guided sensitizer delivery for the potential photodynamic therapy of hypoxic structures requiring cytotoxic control.