Department of Chemistry, University of Tsukuba, Tsukuba, 305-8571, Japan.
Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Tsukuba, 305-8571, Japan.
J Fluoresc. 2023 Nov;33(6):2431-2439. doi: 10.1007/s10895-023-03230-2. Epub 2023 Apr 24.
Water-soluble cationic gallium(III)-Pc complex (GaPc) is capable of photogenerating ROSs but does not exhibit photocytotoxicity in vivo. GaPc binds selectively, through a π-π stacking interaction, to the 5'-terminal G-quartet of a G-quadruplex DNA. The photo-excited state of GaPc of the complex is effectively quenched through electron transfer (ET) from the ground state of DNA guanine (G) bases to the photo-excited state of GaPc (ET). Hence the loss of the photocytotoxicity of GaPc in vivo is most likely to be due to the effective quenching of its photo-excited state through ET. In this study, we investigated the photochemical properties of GaPc in the presence of duplex DNAs formed from a series of sequences to elucidate the nature of ET. We found that ET is allowed in electrostatic complexes between GaPc and G-containing duplex DNAs and that the rate of ET (k) can be reasonably interpreted in terms of the distance between Pc moiety of GaPc and DNA G base in the complex. We also found that the quantum yields of singlet oxygen (O) generation (Φs) determined for the GaPc-duplex DNA complexes were similar to the value reported for free GaPc (Fujishiro R, Sonoyama H, Ide Y, et al (2019) J Inorg Biochem 192:7-16), indicating that ET in the complex is rather limited. These results clearly demonstrated that photocytotoxicity of GaPc is crucially affected by ET. Thus elucidation of interaction of a photosensitizer with biomolecules, i.e., an initial process in PDT, would be helpful to understand its subsequent photochemical processes.
水溶性阳离子镓(III)-Pc 配合物（GaPc）能够光生成 ROS，但在体内不表现出光细胞毒性。GaPc 通过π-π 堆积相互作用选择性地结合到 G-四链体 DNA 的 5'-端 G-四聚体。配合物中 GaPc 的光激发态通过从 DNA 鸟嘌呤（G）碱基的基态到 GaPc 的光激发态的电子转移（ET）有效地猝灭（ET）。因此，GaPc 在体内丧失光细胞毒性很可能是由于其光激发态通过 ET 有效地猝灭。在这项研究中，我们研究了 GaPc 在一系列序列形成的双链 DNA 存在下的光化学性质，以阐明 ET 的性质。我们发现，在 GaPc 和含 G 的双链 DNA 之间的静电复合物中允许 ET，并且 ET 速率（k）可以根据 GaPc 中 Pc 部分和复合物中 DNA G 碱基之间的距离合理地解释。我们还发现，对于 GaPc-双链 DNA 配合物确定的单线态氧（O）生成（Φs）量子产率与报道的游离 GaPc（Fujishiro R，Sonoyama H，Ide Y，等（2019）J Inorg Biochem 192：7-16）的值相似，表明复合物中的 ET 相当有限。这些结果清楚地表明，GaPc 的光细胞毒性受到 ET 的严重影响。因此，阐明光敏剂与生物分子的相互作用，即 PDT 的初始过程，将有助于理解其随后的光化学过程。
