| Περίληψη: | Oxidative stress is an imbalance between oxidants and antioxidants in favor of the former, potentially leading to damage. Major oxidants in cells include reactive oxygen and nitrogen species (RONS) and their increase has been linked to exacerbate the pathogenesis of several diseases. Successful mapping of oxidative stress can yield in-depth knowledge of disease etiology and would be of paramount help in designing strategies for early diagnosis and monitoring treatment progress. Electron paramagnetic resonance (EPR) spectroscopy coupled with exogenous probes is a well-established method for the in vitro detection of RONS. In one application, paramagnetic aminoxyl (nitroxide) radicals are employed in studying oxidative stress owing to their capability of being redox sensitive. However, successful transition of in vitro to in vivo EPR detection of cellular redox status via molecular probes is still hampered by several challenges linked to probe delivery parameters.
Aminoxyl probe NB111 (5-acetoxymethoxycarbonyl- 1,1,3,3-tetraethylisoindolin-2-yloxyl) has been synthesized previously in Dr. Fabienne Peyrot’s lab. The hydrophobic nature of the NB111 probe posed challenges for its in vivo delivery. To allow intravenous administration of NB111, we aimed at developing nanoemulsions (NE) with high loading efficiency, long shelf life stability and no interference of NE constituents with NB111. Emulsification tests and pseudoternary diagrams were used to optimize the composition of NEs. Coarse emulsions were prepared using high shear homogenizer followed by microfluidization to yield NEs. Dynamic light scattering confirmed a mean droplet size below 200 nm with a PDI value of less than 0.1. Moreover, stability studies, carried out at room temperature and 40°C, showed no significant increase in the droplet size or PDI values. X-band EPR spectroscopy and HPLC quantification results showed that NB111 probe retained its initial EPR spectrum in selected NEs with maximum amount of probe being quantified in hydrophobic phase. Our developed NEs for NB111 probe could be further optimized for L-band EPR spectroscopy detection which could be investigated for in vivo oxidative stress mapping.
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