Dataset Information

Excited-State Dynamics of a Two-Photon-Activatable Ruthenium Prodrug.

ABSTRACT: We present a new approach to investigate how the photodynamics of an octahedral ruthenium(II) complex activated through two-photon absorption (TPA) differ from the equivalent complex activated through one-photon absorption (OPA). We photoactivated a Ru(II) polypyridyl complex containing bioactive monodentate ligands in the photodynamic therapy window (620-1000?nm) by using TPA and used transient UV/Vis absorption spectroscopy to elucidate its reaction pathways. Density functional calculations allowed us to identify the nature of the initially populated states and kinetic analysis recovers a photoactivation lifetime of approximately 100?ps. The dynamics displayed following TPA or OPA are identical, showing that TPA prodrug design may use knowledge gathered from the more numerous and easily conducted OPA studies.

SUBMITTER: Greenough SE

PROVIDER: S-EPMC4797363 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Excited-State Dynamics of a Two-Photon-Activatable Ruthenium Prodrug.

Greenough Simon E SE Horbury Michael D MD Smith Nichola A NA Sadler Peter J PJ Paterson Martin J MJ Stavros Vasilios G VG

Chemphyschem : a European journal of chemical physics and physical chemistry 20160106 2

We present a new approach to investigate how the photodynamics of an octahedral ruthenium(II) complex activated through two-photon absorption (TPA) differ from the equivalent complex activated through one-photon absorption (OPA). We photoactivated a Ru(II) polypyridyl complex containing bioactive monodentate ligands in the photodynamic therapy window (620-1000 nm) by using TPA and used transient UV/Vis absorption spectroscopy to elucidate its reaction pathways. Density functional calculations al ...[more]

PMID: 26632426

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Project description:6-Thioguanine, an immunosuppressant and anticancer prodrug, has been shown to induce DNA damage and cell death following exposure to UVA radiation. Its metabolite, 6-thioguanosine, plays a major role in the prodrug's overall photoreactivity. However, 6-thioguanine itself has proven to be cytotoxic following UVA irradiation, warranting further investigation into its excited-state dynamics. In this contribution, the excited-state dynamics and photochemical properties of 6-thioguanine are studied in aqueous solution following UVA excitation at 345 nm in order to provide mechanistic insight regarding its photochemical reactivity and to scrutinize whether N9-glycosylation modulates its phototoxicity in solution. The experimental results are complemented with time-dependent density functional calculations that include solvent dielectric effects by means of a reaction-field solvation model. UVA excitation results in the initial population of the S?(??*) state, which is followed by ultrafast internal conversion to the S?(n?*) state and then intersystem crossing to the triplet manifold within 560 ± 60 fs. A small fraction (ca. 25%) of the population that reaches the S?(n?*) state repopulates the ground state. The T?(??*) state decays to the ground state in 1.4 ± 0.2 ?s under N?-purged conditions, using a 0.2 mM concentration of 6-thioguanine, or it can sensitize singlet oxygen in 0.21 ± 0.02 and 0.23 ± 0.02 yields in air- and O?-saturated solution, respectively. This demonstrates the efficacy of 6-thioguanine to act as a Type II photosensitizer. N9-glycosylation increases the rate of intersystem crossing from the singlet to triplet manifold, as well as from the T?(??*) state to the ground state, which lead to a ca. 40% decrease in the singlet oxygen yield under air-saturated conditions. Enhanced vibronic coupling between the singlet and triplet manifolds due to a higher density of vibrational states is proposed to be responsible for the observed increase in the rates of intersystem crossing in 6-thioguanine upon N9-glycosylation.

Dataset Information

Excited-State Dynamics of a Two-Photon-Activatable Ruthenium Prodrug.

Publications

Excited-State Dynamics of a Two-Photon-Activatable Ruthenium Prodrug.

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