Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University , Tianjin 300070, P. R. China.
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
J Org Chem. 2017 Jan 6;82(1):588-596. doi: 10.1021/acs.joc.6b02590. Epub 2016 Dec 28.
Tetrathiatriarylmethyl (TAM, trityl) radicals have attracted considerable attention as spin probes for biological electron paramagnetic resonance (EPR) spectroscopy and imaging owing to their sharp EPR singlet signals and high biostability. However, their in vivo applications were limited by the short blood circulation lifetimes and strong binding with albumins. Our previous results showed that PEGylation is a feasible method to overcome the issues facing in vivo applications of TAM radicals. In the present study, we synthesized a series of new PEGylated TAM radicals (TTP1, TPP2, TNP1, TNP2, d-TNP1, and d-TNP3) containing various lengths and numbers of mPEG chains. Our results found that the pattern of PEGylation exerts an important effect on physicochemical properties of the resulting TAM radicals. Dendritic PEGylated TAM radicals, TNP1 and TNP2, have higher water solubility and lower susceptibility for self-aggregation than their linear analogues TPP1 and TPP2. Furthermore, dendritic PEGylated TAM radicals exhibit extremely high stability toward various biological oxidoreductants as well as in rat whole blood, liver homogenate, and following in vivo intravenous administration in mice. Importantly, the deuterated derivatives, especially d-TNP3, exhibit excellent properties including the sharp and O-sensitive EPR singlet signal, good biocompatibility, and prolonged kinetics with half-life time of ≥10 h in mice. These PEGylated TAM radicals should be suitable for a wide range of applications in in vivo EPR spectroscopy and imaging.
四硫代三芳基甲基（TAM，三苯甲基）自由基因其尖锐的单重态 EPR 信号和高生物稳定性而被广泛应用于生物电子顺磁共振（EPR）光谱学和成像作为自旋探针。然而，由于其体内循环半衰期短和与白蛋白结合能力强，其体内应用受到限制。我们之前的研究结果表明，聚乙二醇化是克服 TAM 自由基体内应用问题的一种可行方法。在本研究中，我们合成了一系列新型聚乙二醇化 TAM 自由基（TTP1、TPP2、TNP1、TNP2、d-TNP1 和 d-TNP3），它们含有不同长度和数量的 mPEG 链。我们的研究结果发现，聚乙二醇化模式对生成的 TAM 自由基的物理化学性质有重要影响。树枝状聚乙二醇化 TAM 自由基 TNP1 和 TNP2 具有较高的水溶性和较低的自聚集倾向，而其线性类似物 TPP1 和 TPP2 则具有较高的水溶性和较低的自聚集倾向。此外，树枝状聚乙二醇化 TAM 自由基对各种生物氧化还原试剂以及在大鼠全血、肝匀浆中的稳定性极高，在小鼠体内静脉注射后也具有极高的稳定性。重要的是，氘代衍生物，特别是 d-TNP3，具有优异的性质，包括尖锐的、对 O 敏感的 EPR 单重态信号、良好的生物相容性和延长的动力学半衰期≥10 h。这些聚乙二醇化 TAM 自由基应适用于广泛的体内 EPR 光谱学和成像应用。
