Singlet oxygen production from photodynamic sensitizers

Foote, Christopher S.; Dobrowolski, Diane C.

doi:10.1016/0047-2670(84)87057-4

Cited by 7 publications

(3 citation statements)

References 1 publication

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“…A photosensitizer can initiate these reactions primarily in three ways. The excited photosensitizer reacts directly by Type I photosensitization or photocycloaddition reactions, or it can transfer its energy to 3 O 2 through a Type II photosensitization mechanism . These reactions can generate highly reactive oxygen species such as singlet oxygen, superoxide and hydrogen peroxide, which then go on to damage biomolecules .…”

Section: Clinical Relevance and Applications Of Thiobasesmentioning

confidence: 99%

Photochemical and Photodynamical Properties of Sulfur‐Substituted Nucleic Acid Bases,

Ashwood

Pollum

Crespo‐Hernández

2018

Photochem & Photobiology

115

132

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Sulfur-substituted nucleobases (a.k.a., thiobases) are among the world's leading prescriptions for chemotherapy and immunosuppression. Long-term treatment with azathioprine, 6-mercaptopurine and 6-thioguanine has been correlated with the photoinduced formation of carcinomas. Establishing an in-depth understanding of the photochemical properties of these prodrugs may provide a route to overcoming these carcinogenic side effects, or, alternatively, a basis for developing effective compounds for targeted phototherapy. In this review, a broad examination is undertaken, surveying the basic photochemical properties and excited-state dynamics of sulfur-substituted analogs of the canonical DNA and RNA nucleobases. A molecular-level understanding of how sulfur substitution so remarkably perturbs the photochemical properties of the nucleobases is presented by combining experimental results with quantum-chemical calculations. Structure-property relationships demonstrate the impact of site-specific sulfur substitution on the photochemical properties, particularly on the population of the reactive triplet state. The value of fundamental photochemical investigations for driving the development of ultraviolet-A chemotherapeutics is showcased. The most promising photodynamic agents identified thus far have been investigated in various carcinoma cell lines and shown to decrease cell proliferation upon exposure to ultraviolet-A radiation. Overarching principles have been elucidated for the impact that sulfur substitution of the carbonyl oxygen has on the photochemical properties of the nucleobases.

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Section: Clinical Relevance and Applications Of Thiobasesmentioning

confidence: 99%

Photochemical and Photodynamical Properties of Sulfur‐Substituted Nucleic Acid Bases,

Ashwood

Pollum

Crespo‐Hernández

2018

Photochem & Photobiology

115

132

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“…Photosensitization-induced oxidation involves generation of a strong oxidizing agent, singlet oxygen, upon illumination of a sensitizer molecule with an appropriate wavelength of light. Singlet oxygen oxidizes plasmogenic lipids and thus causes disruption of biomembranes [31-39]. This mechanism is currently used in photodynamic therapy to disrupt the membrane of cancer cells and induce cell death.…”

Section: Mechanisms Of Light-triggered Release From Nanocarriersmentioning

confidence: 99%

Photochemical mechanisms of light-triggered release from nanocarriers

Fomina

Sankaranarayanan

Almutairi

2012

Advanced Drug Delivery Reviews

446

375

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Over the last three decades, a handful of photochemical mechanisms have been applied to a large number of nanoscale assemblies that encapsulate a payload to afford spatio-temporal and remote control over activity of the encapsulated payload. Many of these systems are designed with an eye towards biomedical applications, as spatio-temporal and remote control of bioactivity would advance research and clinical practice. This review covers five underlying photochemical mechanisms that govern the activity of the majority of photoresponsive nanocarriers: 1. photo driven isomerization and oxidation, 2. surface plasmon absorption and photothermal effects, 3. photo driven hydrophobicity changes, 4. photo driven polymer backbone fragmentation and 5. photo driven de-crosslinking. The ways in which these mechanisms have been incorporated into nanocarriers and how they affect release is detailed, as well as the advantages and disadvantages of each system.

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“…To some extent the formation yield of the triplet state can be a measure of 1 O 2 production. In general, the formation yields of the triplet state in thiocarbonyl compounds was found to be very efficient, e.g., 0.9 for thiouracils in H 2 O[56], 0.99 for 6-thiopurine in THF,[57] 0.7[58] and 0.6[59] for 4-thiouridine in CH 3 CN, an unity for 4-thiothymidine in an ionic liquid,[60] and 0.8 for thioguanosine in aqueous solution[61], and was quenched by 3 O 2 at a diffusing rate constant of 6.8×10 9 M −1 s −1 . [62] These measurements are in line with our Φ Δ value of 0.58 for 6-TG.…”

Section: Discussionmentioning

confidence: 99%

Quantification of thiopurine/UVA-induced singlet oxygen production

Zhang

Barnes

Zhu

et al. 2011

Journal of Photochemistry and Photobiology A: Chemistry

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Thiopurines were examined for their ability to produce singlet oxygen (1O2) with UVA light. The target compounds were three thiopurine prodrugs, azathioprine (Aza), 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), and their S-methylated derivatives of 6-methylmercaptopurine (me6-MP) and 6-methylthioguanine (me6-TG). Our results showed that these thiopurines were efficient 1O2 sensitizers under UVA irradiation but rapidly lost their photoactivities for 1O2 production over time by a self-sensitized photooxidation of sulfur atoms in the presence of oxygen and UVA light. The initial quantum yields of 1O2 production were determined to be in the range of 0.30–0.6 in aqueous solutions. Substitution of a hydrogen atom with a nitroimidazole or methyl group at S decreased the efficacy of photosensitized 1O2 production as found for Aza, me6-MP and me6-TG. 1O2-induced formation of 8-oxo-7,8-dihydro-2’-dexyguanosine (8-oxodGuo) was assessed by incubation of 6-methylthiopurine/UVA-treated calf thymus DNA with human repair enzyme 8-oxodGuo DNA glycosylase (hOGG1), followed by apurinic (AP) site determination. Because more 8-oxodGuo was formed in Tris D2O than in Tris H2O, 1O2 is implicated as a key species in the reaction. These findings provided quantitative information on the photosensitization efficacy of thiopurines and to some extent revealed the correlations between photoactivity and phototoxicity.

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Singlet oxygen production from photodynamic sensitizers

Cited by 7 publications

References 1 publication

Photochemical and Photodynamical Properties of Sulfur‐Substituted Nucleic Acid Bases,

Photochemical and Photodynamical Properties of Sulfur‐Substituted Nucleic Acid Bases,

Photochemical mechanisms of light-triggered release from nanocarriers

Quantification of thiopurine/UVA-induced singlet oxygen production

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