Whole-body In vivo Imaging of Exogenous Nitroxide Probes

2 Whole-body In vivo Imaging of Exogenous Nitroxide Probes. - A number of studies have investigated the distribution and time-course of nitroxide free 

The in vivo distribution of a new, polymer-nitroxide probe, spin-labelled dextran (termed TEMPO-DX) was investigated by Saito et al, who also compared its distribution and pharmacokinetics to that of 3-carbamoyl-proxyl. As expected, it was found that the half-life of the larger molecule was considerably longer than that of 3-carbamoyl-proxyl, and that the TEMPO-DX concentrated in the tumour of a mouse with an Ehrlich s ascites carcinoma. 

Sano et al reported the development and use of another new nitroxyl probe, carboxy-proxyl acetoxymethyl ester (CxP-AM) for brain imaging. Its advantage over previous probe molecules is that it is able to cross the blood-brain barrier, but once inside the brain it is hydrolysed and retained there. In vivo L-band EPRI measurements on mice injected intravenously with a solution of CxP-AM showed that the compound did indeed localise in the brain, in contrast to analogous experiments using two other carboxy-proxyl derivatives, both of which exhibited much more diffuse distributions in the head. The authors point out that, because of its specificity and longevity in the brain, the CxP-AM agent should have potential for the determination of redox status of this organ in models of disease. 

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