EPR spectroscopy, coupled with the use of tetrathiatriarylmethyl (TAM) radicals, has been a reliable method to detect the superoxide radical (O₂^.−). However, the specificity and biocompatibility of TAM radicals need to be further improved. Although derivatization may overcome the drawbacks of current TAM radicals, esterification or amidation through the carboxylic groups greatly changes their redox properties and makes them inert to O₂^.−. Herein, the synthesis of a perthiatriarylmethyl (PST) radical and its dendritic derivatives, PST‐TA and PST‐NA, in which PST is covalently linked with dendrons containing three (TA) and nine (NA) carboxylic acids, respectively. The results show that PST rapidly reacts with O₂^.− to yield a unique quinone methide product. Dendritic modification of PST slightly decreases the reactivities of PST‐TA and PST‐NA, but notably increases their biostability toward various oxidoreductants. The detection limit of PST‐NA to O₂^.− was estimated to be 2.1 nm min⁻¹ over 60 min of detection. Importantly, PST‐NA shows threefold higher sensitivity to O₂^.− in the presence and absence of ascorbic acid than that of the classic spin‐trapping technique. In addition, the application of PST‐NA to detect extracellular O₂^.− generation in stimulated RAW 264.7 macrophages was also explored. This study demonstrates that PST‐NA has great potential for specific detection and quantitation of O₂^.− in extracellular sites.

中文翻译：

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高灵敏度和对超氧化物自由基具有选择性的四硫代三芳基甲基自由基及其树枝状衍生物的合成与表征

EPR光谱，结合使用四硫代三芳基甲基（TAM）自由基，已成为检测超氧化物自由基（O ₂ ^.-）的可靠方法。然而，TAM自由基的特异性和生物相容性需要进一步提高。尽管衍生化可以克服当前TAM自由基的缺点，但是通过羧基进行的酯化或酰胺化极大地改变了它们的氧化还原特性，并使它们对O ₂ ^.-呈惰性。在本文中，合成了四硫杂三芳基甲基（PST）自由基及其树状衍生物PST-TA和PST-NA，其中PST与分别包含三个（TA）和九个（NA）羧酸的树突共价连接。结果表明，PST与O ₂ ^.-迅速反应。产生独特的醌甲基化物产物。PST的树枝状修饰会稍微降低PST-TA和PST-NA的反应性，但会显着提高其对各种氧化还原剂的生物稳定性。在60分钟的检测时间内，PST-NA对O ₂ ^.-的检出限估计为2.1 n m  min ^-1。重要的是，在存在和不存在抗坏血酸的情况下，PST-NA对O ₂ ^.-的敏感性是传统自旋捕集技术的三倍。此外，PST-NA在检测细胞外O ₂ ^{.-中的应用}还研究了在刺激的RAW 264.7巨噬细胞中的生成。这项研究表明，PST-NA在细胞外位点中O ₂ ^.-的特异性检测和定量方面具有巨大的潜力。