Magnetic resonance imaging examinations are frequently carried out using contrast agents to improve the image quality. Practically all clinically used contrast agents are based on paramagnetic metals and lack in selectivity and specificity. A group of stable organic radicals, nitroxides, has raised interest as new metal-free contrast agents for MRI. Their structures can easily be modified to incorporate different functionalities. In the present study, a stable nitroxide TEEPO (2,2,6,6-tetraethylpiperidin-1-oxyl) was linked to a glucose moiety (Glc) to construct a water-soluble, potentially tumor-targeting compound with contrast-enhancing ability. The ability was assessed with in vivo MRI experiments. The constructed TEEPO-Glc agent proved to shorten the T₁ relaxation time in tumor, while the T₁ time in healthy brain tissue remained the same. The results indicate the potential of TEEPO-Glc as a valuable addition to the growing field of metal-free contrast enhancement in MRI-based diagnostics.

中文翻译：

---

使用体内磁共振成像评估基于氮氧化物的造影剂 TEEPO-Glc 的松弛增强特性。


磁共振成像检查经常使用造影剂来提高图像质量。实际上，临床上使用的所有造影剂均基于顺磁性金属，缺乏选择性和特异性。一组稳定的有机自由基（硝基氧）作为新型 MRI 不含金属造影剂引起了人们的兴趣。它们的结构可以很容易地修改以合并不同的功能。在本研究中，稳定的硝基氧 TEEPO（2,2,6,6-四乙基哌啶-1-氧基）与葡萄糖部分 (Glc) 连接，构建了一种水溶性、潜在肿瘤靶向化合物，具有增强对比度的能力。通过体内MRI 实验评估这种能力。事实证明，构建的TEEPO-Glc药物可以缩短肿瘤中的T ₁弛豫时间，而健康脑组织中的T ₁时间保持不变。结果表明，TEEPO-Glc 具有作为 MRI 诊断中不断增长的无金属对比度增强领域的有价值补充的潜力。