Preparation and Characterization of Mitochondrial-Targeted Nitronyl Nitroxide Loaded PLGA Nanoparticles for Brain Injury Induced by Hypobaric Hypoxia in Mice.

Background: Oxidative stress is considered an important mechanism of acute high-altitude brain injury. Imidazole nitronyl nitroxide radicals are a class of stable organic radical scavengers that contain single electrons in their molecules. Therefore, in order to search for compounds with low toxicity and better effect against high-altitude brain injury, the preparation methods of PLGA nanoparticles (TPP-C₆-HPN@PLGA-NPs) loaded with a synthesized mitochondria targeting imidazole nitronyl nitroxide were emphasized and investigated. Furthermore, its protective effect on brain injury caused by low-pressure hypoxia (HH) in mice was evaluated.

Methods: Nanoparticles were prepared by emulsion solvent evaporation method, and the preparation method was optimized by Box Behnken design based on particle size, encapsulation efficiency (EE) and drug loading (DL). Physical characterization and release studies of the optimized NPs were conducted. The high altitude brain injury mice model was selected to evaluate the therapeutic effect of TPP-C₆-HPN@PLGA-NPs in vivo. The histological and biochemical tests were conducted in serum and brain of mice exposed to HH condition.

Results: The nanoparticle size was 120.63 nm, the EE was 89.30%, the DL was 6.82%, the polydispersity index (PDI) was 0.172, and the zeta potential was -22.67 mV under optimal preparation process. In addition, TPP-C₆-HPN@PLGA-NPs owned good stabilities and sustained drug releases. TPP-C₆-HPN@PLGA-NP exhibited lower toxicity than TPP-C₆-HPN and was well uptaken by PC12 cells. Histological and biochemical analysis demonstrated that TPP-C₆-HPN@PLGA-NPs significantly reduced HH induced pathological lesions, oxidative stress, energy dysfunction and inflammation response of brain tissue. Furthermore, nanoparticles did not show significant toxicity to major organs such as the liver and kidneys, as well as hematology in mice.

Conclusion: TPP-C₆-HPN@PLGA-NPs exhibits good stability, low hemolysis rate, sustained release, low toxicity, and long residence time in brain tissue and can be used as a promising formulation for the proper treatment of HH-induced brain damage.