Development of Smart Spin Probes – SonRadIs

Since decades, investigations of pathological and physiological events using spectroscopic techniques became more and more important. Nowadays, such events are investigated at the molecular level and require techniques exhibiting high levels of sensitivity, resolution and specificity of the bioprocess. Furthermore, the ultimate aim of such techniques is to be applied to human being. However, at this time, no techniques exhibit these requirements. Thus, tremendous efforts are performed to develop bioprobes aiming to improve the requirements mentioned above. For spectroscopic applications, beside their biospecificity, these bioprobes must afford a typical spectroscopic signal. This has been partly reached for many bioprocess investigated by MRI, the most common and suitable technique to investigate bioprocess in human beings and animals. Despite many successes, a lot of events still escape to this technique. Hence, the aim of this project is to develop new bioprobes exhibiting high bio-specificity and a very typical signal. For this, we plan to develop molecules suitable to investigate non-radical bioprocess using a radical reaction. Indeed, we plan to prepare a bioprobe (bioalkoxyamine R1R2NOR3) stable, which, in the presence of a specific enzyme, hydrolysis into an alkoxyamine (R1R2NOR4), the latter decomposes spontaneously into alkyl radical (R4.) and nitroxide (R1R2NO.) at physiological temperature. Then, the nitroxide can be easily detected by EPR or by DNP-MRI by its effect on the surrounding molecules. Our project is divided in 3 phases: i) preparation of bioprobes, ii) investigation of their hydrolysis (bioactivation by enzymes) and homolyse (spontaneous fragmentation into radicals at physiological temperature) as well as the resistance of nitroxides to bio-reductants, and iii) application in DNP-MRI to investigate in a non-invasive way the proteolysis in living mice. A Smart Spin Probe is then defined as a radical-type probe bearing a typical signal which appears only in the presence of the investigated biological event.