Synthesis and biological testing of aminoxyls designed for long-term retention by living cells
作者:Gerald M. Rosen、Scott R. Burks、Mark J. Kohr、Joseph P. Y. Kao
DOI:10.1039/b415586f
日期:——
Owing to recent advances in electron paramagnetic resonance (EPR) imaging methodologies, it is now potentially possible to track and image, in real time in vivo, cells that had been tagged with aminoxyl spin probes. We had previously reported that living cells can accumulate 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl [1] to high (millimolar) intracellular concentrations through passive incubation with the corresponding acetoxymethyl (AM) ester [2]. In the present study, we show that under physiological conditions aminoxyl [1] is rapidly extruded by cells through an organic anion transport mechanism, resulting in an intracellular exponential lifetime (t1/e or τ) of just 9.84 min at 37 °C. Through successive rational structural modifications, we arrived at (2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-ylmethyl)amine-N,N-diacetic acid [10], which can still be accumulated by cells to high intracellular concentrations, but which, with an intracellular exponential lifetime of τ
= 114 min, is well retained by cells for long periods of time, where one expects 14% retention even after 5 h. These results suggest that it should be feasible to use EPR imaging to perform in vivo tracking of populations of cells that have accumulated high intracellular levels of aminoxyls.
由于最近在电子顺磁共振(EPR)成像方法学上的进展,现在有可能实时追踪和体内成像那些已被标记氨基氧自由基探针的细胞。我们之前报道过活细胞可以通过被动孵育相应乙酰氧甲基(AM)酯[2]来积累3-羧基-2,2,5,5-四甲基-1-吡咯烷氧基[1]到高水平(毫摩尔)的细胞内浓度。在本研究中,我们展示在生理条件下氨基氧[1]会通过一种有机阴离子转运机制迅速被细胞排出,导致其在细胞内的指数寿命(t1/e或τ)在37°C时仅为9.84分钟。通过连续的合理结构改造,我们得到了(2,2,5,5-四甲基吡咯烷-1-氧基-3-基甲基)胺-N,N-二乙酸[10],这种物质细胞仍能积累至高细胞内浓度,但在细胞内的指数寿命τ = 114分钟,能很好地被细胞长时间保留,即使在5小时后仍预计有14%的保留。这些结果表明,利用EPR成像对积累了高水平氨基氧的细胞群进行体内追踪应该是可行的。