Kao Joseph P Y, Barth Eugene D, Burks Scott R, Smithback Philip, Mailer Colin, Ahn Kang-Hyun, Halpern Howard J, Rosen Gerald M
Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA.
Magn Reson Med. 2007 Oct;58(4):850-4. doi: 10.1002/mrm.21388.
Recent advances in electron paramagnetic resonance (EPR) imaging have made it possible to image, in real time in vivo, cells that have been labeled with nitroxide spin probes. We previously reported that cells can be loaded to high (millimolar) intracellular concentrations with (2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-ylmethyl)amine-N,N-diacetic acid by incubation with the corresponding acetoxymethyl (AM) ester. Furthermore, the intracellular lifetime (t(1/e)) of this nitroxide is 114 min-sufficiently long to permit in vivo imaging studies. In the present study, at a gradient of approximately 50 mT/m, we acquire and compare EPR images of a three-tube phantom, filled with either a 200-microM solution of the nitroxide, or a suspension of cells preincubated with the nitroxide AM ester. In both cases, 3-mm resolution images can be acquired with excellent signal-to-noise ratios (SNRs). These findings indicate that cells well-loaded with nitroxide are readily imageable by EPR imaging, and that in vivo tracking studies utilizing such cells should be feasible.
电子顺磁共振（EPR）成像技术的最新进展使得实时体内成像已用氮氧化物自旋探针标记的细胞成为可能。我们之前报道过，通过与相应的乙酰氧基甲基（AM）酯一起孵育，细胞可以被加载到高（毫摩尔）细胞内浓度的（2,2,5,5-四甲基吡咯烷-1-氧基-3-基甲基）胺-N,N-二乙酸中。此外，这种氮氧化物的细胞内寿命（t(1/e)）为114分钟，足够长以允许进行体内成像研究。在本研究中，在大约50 mT/m的梯度下，我们采集并比较了一个三管模型的EPR图像，该模型填充有200 μM的氮氧化物溶液或预先用氮氧化物AM酯孵育的细胞悬液。在这两种情况下，都可以获得具有出色信噪比（SNR）的3毫米分辨率图像。这些发现表明，富含氮氧化物的细胞很容易通过EPR成像进行成像，并且利用此类细胞进行体内追踪研究应该是可行的。
