Ataci Nese, Kazancioglu Elif Ozcelik, Kalındemirtas Ferdane Danisman, Kuruca Serap Erdem, Arsu Nergis
Yildiz Technical University, Davutpasa Campus, Department of Chemistry, 34220 Istanbul, Turkey.
Istanbul University, Faculty of Medicine, Department of Physiology, 34093 Istanbul, Turkey.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Oct 5;239:118491. doi: 10.1016/j.saa.2020.118491. Epub 2020 May 16.
In this study, a thioxanthone derivative, 2-Thioxanthone Thioacetic Acid (TXSCHCOOH) was used to analyze the type of binding to calf thymus DNA in a physiological buffer (Tris-HCl buffer solution, pH:7.0). Several spectroscopic techniques were employed including UV-Vis absorption and fluorescence emission spectroscopy and viscosity measurements were also used to clarify the binding mode of TXSCHCOOH to ct-DNA. The intrinsic binding constant Kb of TXSCHCOOH-ct-DNA was found as 2.5 × 10 M from the absorption studies. Increasing of fluorescence emission intensity was found approximately 74.4% by adding ct-DNA to the TXSCHCOOH solution. Fluorescence microscopy was employed to display imaging of the TXSCHCOOH-ct-DNA solution. Increasing of the iodide quenching effect was observed when TXSCHCOOH was added to the double stranded DNA and the calculated quenching constants of TXSCHCOOH and TXSCHCOOH-ct-DNA were found to be 1.89 × 10 M and 1.19 × 10 M, respectively. Additionally, the iodide quenching experiment was conducted with single stranded DNA which led to a high Ksv value. All the experimental results including the viscosity values of ct-DNA with TXSCHCOOH demonstrated that the binding of TXSCHCOOH to ct-DNA was most likely groove binding. Furthermore, TXSCHCOOH was found to be an A-T rich minor groove binder. This was confirmed by the displacement assays with Hoechst 33258 compared to Ethidium Bromide. The in vitro cytotoxic activity measurements were performed by MTT assay on HT29 cell line for 72 h. TXSCHCOOH exhibited notable cytotoxic activities compared to the standard chemotherapy drugs, fluorouracil (5-FU), cisplatin in tumorigenic HT29 cell line. The 50% growth-inhibitory concentration (IC) for TXSCHCOOH was 19,8 μg/mL while 5-FU and cisplatin were 28.9 μg/mL, 20 μg/mL, respectively. The increase in cytotoxic effect when TXSCHCOOH is activated by light indicates the potential of being theranostic cancer drug candidate.
在本研究中，一种噻吨酮衍生物，2-噻吨酮硫代乙酸（TXSCHCOOH）被用于在生理缓冲液（Tris-HCl缓冲溶液，pH：7.0）中分析其与小牛胸腺DNA的结合类型。采用了多种光谱技术，包括紫外-可见吸收光谱和荧光发射光谱，还进行了粘度测量以阐明TXSCHCOOH与小牛胸腺DNA（ct-DNA）的结合模式。通过吸收研究发现TXSCHCOOH与ct-DNA的固有结合常数Kb为2.5×10⁶ M。向TXSCHCOOH溶液中加入ct-DNA后，荧光发射强度增加了约74.4%。采用荧光显微镜对TXSCHCOOH-ct-DNA溶液进行成像。当向双链DNA中加入TXSCHCOOH时，观察到碘化物猝灭效应增强，计算得出TXSCHCOOH和TXSCHCOOH-ct-DNA的猝灭常数分别为1.89×10⁵ M和1.19×10⁵ M。此外，对单链DNA进行了碘化物猝灭实验，得到了较高的Ksv值。所有实验结果，包括ct-DNA与TXSCHCOOH的粘度值，都表明TXSCHCOOH与ct-DNA的结合很可能是沟槽结合。此外，发现TXSCHCOOH是一种富含A-T的小沟结合剂。与溴化乙锭相比，用Hoechst 33258进行的置换试验证实了这一点。通过MTT法对HT29细胞系进行72小时的体外细胞毒性活性测量。与标准化疗药物氟尿嘧啶（5-FU）、顺铂相比，TXSCHCOOH在致瘤性HT29细胞系中表现出显著的细胞毒性活性。TXSCHCOOH的50%生长抑制浓度（IC₅₀）为19.8 μg/mL，而5-FU和顺铂分别为28.9 μg/mL、20 μg/mL。当TXSCHCOOH被光激活时细胞毒性效应增强，这表明其有成为治疗诊断用癌症候选药物的潜力。
