College of Chemistry, Sichuan University, 29 Wangjiang Road, Chengdu 610064, China.
Nanoscale. 2018 May 10;10(18):8477-8482. doi: 10.1039/c8nr01355a.
Overexpression and crystallization of uric acid have been recognized as the course of hyperuricemia and gout, which is produced via xanthine oxidase (XOD)-catalyzed oxidation of xanthine. Therefore, the medicinal therapy of hyperuricemia and gout is majorly based on the inhibition of the XOD enzymatic pathway. The spectroscopic nature of xanthine and uric acid, namely both absorption (near the ultraviolet region) and emission (non-fluorescent) characteristics, hinders optical assay development for XOD analysis. Therefore, the state-of-the-art analysis of XOD and the screening of XOD inhibitors are majorly based on chromatography. Here, we found the near ultraviolet absorption of uric acid overlapped well with the absorption of a large bandgap semiconductor quantum dots, ZnS. On the other hand, the intrinsic weak fluorescence of ZnS QDs can be substantially improved via transition metal ion doping. Therefore, herein, we developed an inner filter effect-based assay for XOD analysis and inhibitor screening with Mn-doped ZnS QDs. The phosphorescence of Mn-doped ZnS QDs could be quenched by uric acid generated from xanthine catabolism by XOD, leading to the phosphorescence turn-off detection of XOD with a limit of detection (3σ) of 0.02 U L-1. Furthermore, the existence of XOD inhibitors could inhibit the XOD enzymatic reaction, resulting in weakened phosphorescence quenching. Therefore, the proposed assay could also be explored for the facile screening analysis of XOD inhibitors, which is important for the potential medicinal therapy of hyperuricemia and gout.
尿酸的过度表达和结晶被认为是高尿酸血症和痛风的过程，这是通过黄嘌呤氧化酶（XOD）催化黄嘌呤氧化产生的。因此，高尿酸血症和痛风的药物治疗主要基于抑制 XOD 酶途径。黄嘌呤和尿酸的光谱性质，即吸收（近紫外区）和发射（非荧光）特性，阻碍了用于 XOD 分析的光学测定法的发展。因此，XOD 的最新分析和 XOD 抑制剂的筛选主要基于色谱法。在这里，我们发现尿酸的近紫外吸收与大带隙半导体量子点 ZnS 的吸收很好地重叠。另一方面，通过掺杂过渡金属离子可以大大提高 ZnS QD 的本征弱荧光。因此，本文开发了一种基于内滤效应的 XOD 分析和抑制剂筛选方法，使用 Mn 掺杂的 ZnS QD。Mn 掺杂的 ZnS QD 的磷光可以被 XOD 催化黄嘌呤代谢产生的尿酸猝灭，从而实现 XOD 的磷光关闭检测，检测限（3σ）为 0.02 U L-1。此外，XOD 抑制剂的存在可以抑制 XOD 的酶促反应，导致磷光猝灭减弱。因此，该方法还可以用于 XOD 抑制剂的简便筛选分析，这对于高尿酸血症和痛风的潜在药物治疗很重要。
