Qingyue Da,1,2 Min Xu,3,4 Yiting Tian,2 Huiping Ma,2 Haibo Wang,3 Linlin Jing1,2 

1Department of Pharmacy, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, 710061, People’s Republic of China; 2Department of Pharmacy, The 940th Hospital of Joint Logistics Support Force of PLA, Lanzhou, Gansu, 730050, People’s Republic of China; 3Department of Chemistry, School of Pharmacy, The Air Force Medical University, Xi’an, 710032, People’s Republic of China; 4The Third Stationed Outpatient Department, General Hospital of Central Theater Command, Wuhan, 430070, People’s Republic of China

Correspondence: Linlin Jing, Department of Pharmacy, The First Affiliated Hospital of Xi’an Jiaotong University, No. 277 Yanta West Road, Yanta District, Xi’an, Shaanxi, 710061, People’s Republic of China, Tel +86-029-85323537, Email jinglinlin@xjtufh.edu.cn Haibo Wang, Department of Chemistry, School of Pharmacy, The Air Force Medical University, No. 169, Changle West Road, Xi’an, Shaanxi, 710032, People’s Republic of China, Tel +86-029-84774473, Email haibo7691@fmmu.edu.cn

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.

Keywords: nitronyl nitroxide, mitochondrial-targeted, PLGA nanoparticles, characterization, high altitude brain injury