Introduction: Traumatic brain injury (TBI) is a major cause of death and disability worldwide, leading to significant personal suffering and high costs to society. Free radicals have been implicated in neurological damage following TBI. The mitochondrial respiratory chain represents the largest source and target of free radicals during periods of oxidative stress and TBI. We hypothesize that a concentrated delivery of antioxidants to the mitochondrial site of action will provide for a more efficacious neutralization of free radical species, maximized histological, and improved functional recovery when compared to untargeted free radical scavengers in models of TBI.
Methods: Silica nano particles will be synthesized and doubly functionalized with a free radical scavenger and fluorescent chemical moiety. TEMPO will be utilized as the radical scavenger, while fluorescein will serve as a covalently-attached luminescent tracker. Localization of the nanoparticles will be assessed by fluorescence microscopy. Antioxidant efficacy in the mitochondria will be assessed by oxidation-dependent fluorescence for apparent decreases of free radical populations via an in vitro model of TBI using a custom-designed stretch-pressure apparatus. Markers of cellular death, including caspase-3 activation, mitochondrial cytochrome c externalization, phosphatidylserine externalization, and DNA fragmentation will be quantified in neurons exposed to the in vitro TBI model.
Results: Antioxidant nanoparticles were synthesized and evaluated in vitro in macrophages to assess uptake parameters. They demonstrated robust uptake as measured by fluorescence microscopy, which in fact localized to mitochondria as the source of free radical production and electron chain dysfunction. Moreover free radical production was blunted in treated cells. Cell death markers were similarly improved.
Conclusions: Nanoparticles allow concentrated delivery of complex pharmacophore payloads to cells. In particular, free radical production was severely blunted in models of traumatic brain injury. Markers of cell death were similarly improved. Safety and in vivo efficacy will be evaluated in future studies.
Patient Care: TBI has complicated mechanistic pathways, of which mitochondrial dysfunction and free radical production plays a key role. These work will allow the development of future targeted drug technologies and may provide improvement in patient outcomes following TBI.
Learning Objectives: By the conclusion of this session, participants should be able to 1) recognize the importance of free radicals in traumatic brain injury, 2) understand the utility of nanoparticles to delivery antioxidants, 3) antioxidant nanoparticles limit free radical production in vitro.