PEG化氘代单磷酸三苯甲基自由基的高效合成及性能研究（英文）

Efficient Synthesis and Characterization of PEGylated/Deuterated Derivatives of Monophosphonated Tetrathiatriarylmethyl Radicals

电子顺磁共振(EPR)波谱联用外源性自旋探针技术是测量体内外pH的有效手段.有研究表明,单磷酸取代三苯甲基(p1TAM)自由基是目前用于检测pH的最理想的EPR探针.然而,这类探针的合成产率低、易受蛋白影响,极大限制了其生物应用.针对上述问题,本文提出了高效合成p1TAM自由基的方法,使其总产率从文献报道的1.6%提高到了25%;同时采用PEG修饰的方法避免了白蛋白(BSA)对其产生的干扰.进一步氘代实验结果证实:非氘代PEG化(p1TAM-H)衍生物(POP)虽与氘代PEG化(p1TAM-D)衍生物(dPOP)具有相似的pH敏感性(其pKa分别为6.80和6.79),但POP的EPR谱图较为复杂,而dPOP无论在低pH还是在高pH条件下均具有简单的EPR双峰信号;而且,dPOP具有比POP和p1TAM-H更好的检测灵敏性;此外,dPOP还具有较好的生物稳定性和氧气敏感性.因此,dPOP能够用来同时检测pH和氧气,有望在生物医学方面得到更好的应用.

Electron paramagnetic resonance (EPR) with the use of exogenous spin probes is an indispensable tool to measure pH in vitro and in vivo. Monophosphonated tetrathiatriarylmethyl (p1TAM) radicals are so far the most promising EPR probes for pH measurement. However, their biological applications were limited by extremely low efficiency in synthesis and potential albumin binding, such that they could not be administered systematically. In the present work, an efficient procedure for p1TAM synthesis was reported, with a total yield of 25% from the corresponding triarylmethanol (compared to 1.6% with the commonly used procedure). Further PEGylation prevented the interaction between p1TAM and albumin. The EPR spectra of nondeuterated (POP) and deuterated (dPOP) PEGylated derivatives of p1TAM were also recorded at different pH values. The two probes had similar pH sensitivities with p Ka values of 6.80 and 6.79, respectively. POP had a much more complex EPR spectrum than dPOP, with the latter always exhibiting simple EPR doublet signals regardless of the pH. These results suggested that dPOP is more advantageous for pH measurement, relative to POP and p1TAM. Moreover, dPOP was shown to have excellent biological stability and high O2 sensitivity, and thus might have the potential to be used as the probe for simultaneous pH and O2 measurements in biological system.