电子顺磁共振（EPR）持有对检测体系无创性、灵敏性、特异性及合适的磁场穿透深度等特质，是目前氧化还原态活体检测与成像的重要方法。高性能探针开发能有效增强EPR及相关技术的生物医学应用。四硫取代三苯甲基（trityl）自由基拥有优越的EPR波谱性质和高度的生物稳定性，是一类深受EPR领域关注的新兴探针，但在检测和成像氧化还原态方面却鲜有报道。因此，本项目拟利用trityl的稳定性，将其作为“报告基团”，同时开发对超氧阴离子自由基、生物巯基或整体氧化还原态敏感的trityl或氮氧自由基作为“传感基团”，通过二者的共价连接构建高灵敏、高选择且以谱线比例方式检测氧化还原态的双自由基探针；通过分子内连接PEG链和穿膜小肽LMWP赋予探针透膜性，并增强其活体应用潜质；在细胞和活体层面阐明双自由基探针用于检测与成像组织细胞内氧化还原态的潜质，并建立小鼠心肌缺血再灌注损伤与组织氧化还原微环境变化的相关性。

Owing to the noninvasive nature, sensitivity, specificity as well as reasonable magnetic field depth of penetration in animals, electron paramagnetic resonance (EPR) spectroscopy/imaging has been established as an important technique for the in vivo measurement and mapping of redox status. The development of stable radical probes can effectively expand biomedical applications of EPR and related techniques. Tetrathiatriarylmethyl (trityl) radicals have accepted intense attention in the field of EPR owing to their outstanding EPR spectral properties and high stability. However, the applications of trityl radicals in the measurement and mapping of redox status were limited due to their relative inertness to biological reductants and oxidants. Therefore, this project will focus on the development of highly stable trityl “reporting” groups as well as superoxide radical-, biothiol- or total redox status-sensitive “sensing” groups. These two kinds of groups will be covalently conjugated to afford highly sensitive and selective biradical probes for ratiometric measurement of the redox parameters. Then, the modification of the probes with PEG chains and the cell penetrating peptide LMWP endows them with cellular permeability and enhance their in vivo application potential. Finally, these cell-permeable biradical probes will be used to measure redox parameters in cellular and in vivo systems and further investigate the correlation of the change of the redox microenvironment with the myocardial ischemia-reperfusion injury in mice.