Abstract
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Objectives: Ischemic reperfusion injury occurs as a result of vessel obstruction, which will block the blood supply to the brain and cause damage. Once the obstruction is removed, blood reperfusion will initiate another round of brain injury. The major culprits of ischemic stroke are reactive oxygen species (ROS) generated during this process. Here, we aim to safely delivery DNA nanocage framework to protect the brain from ischemic stroke in rat models via intrathecal injection and subsequent ROS scavenging.
Methods: DNA nanocages were assembled by annealing four DNA oligonucleotides with designated sequences to form a 3D pyramid framework. DNA cages were labeled with Zr-89 for PET imaging and IRDye 800CW for fluorescence imaging. At different time points after intrathecal injection into Sprague Dawley rats, biodistribution of DNA nanocages was investigated. Later, rat models of ischemic reperfusion injury were established via middle cerebral artery occlusion (MCAO) surgery. Treatment effects of DNA nanocages were compared with PBS treatment group (negative control) and sham group (positive control) by using magnetic resonance imaging (MRI) to measure the infarct area. TTC staining and confocal imaging of the brain tissue were performed to validate the imaging results and the treatment mechanism of using DNA nanocages.
Results: DNA nanocages could be prepared using the self-assembly method with high purity. PET imaging with Zr-89 labeled DNA nanocages showed that this structure may enter the brain as early as 15 min after intrathecal injection and stay for at least 12 h. Fluorescent imaging using 800CW-labeled DNA nanocage validated its biodistribution. When administrated to rat models of ischemic stroke, we found significantly decreased brain infarct volume as evidenced by MRI and TTC staining of brain tissues ex vivo. Detailed mechanism studies demonstrated that DNA nanocages may effectively scavenge ROS in vitro and lower down the expression of Caspase-3 in rats with ischemic stroke.
Conclusions: Zr-89 and 800CW labeled DNA nanocage framework could be safely delivered to rat brains via intrathecal injection and imaged using PET imaging and fluorescence imaging. The delivered DNA nanocages may protected rats from ischemic stroke by neutralizing ROS. This DNA framework holds great promise for stroke prevention and potential clinical translation.