Intrathecal injection of aptamer-conjugated DNA framework for the treatment of cerebral ischemia/reperfusion injury.

Objectives: Stroke is the leading cause of global disability, and the annual cost of stroke will rise 129% from 2010 to 2030. Cerebral ischemia-reperfusion injury (IRI) has been considered the main culprit and one of the primary obstacles in the treatment of ischemic strokes, which generates toxic reactive oxygen species (ROS) and inflammatory damage. We aim to alleviate cerebral IRI by intrathecal injection of an aptamer-conjugated framework nuclei acid (FNA) for neuronal protection, which acts as an antioxidant as well as inhibits the recruitment of inflammatory cells and the release of proinflammatory ROS.

Methods: A bipyramidal FNA was conjugated to an anti-fifth component of complement aptamer (aC5a) using a single step annealing procedure (aC5a-FNA). The aC5a-FNA or FNA were functionalized with desferrioxamine-conjugated ssDNA for Zr-89 radiolabeling (⁸⁹Zr-aC5a-FNA or ⁸⁹Zr-FNA). The middle cerebral artery occlusion (MCAO) surgery model was used to induce IRI. Following intrathecal injection of ⁸⁹Zr-FNA into Sprague Dawley rats with cerebral IRI, the biodistribution was studied using PET imaging. The efficacy of aC5a-FNA treatment was compared to sham, aC5a, FNA, and PBS treated rats three days after MCAO was performed. Magnetic resonance imaging (MRI) was used to confirm the presence of ischemia brain damage. Cerebral IRI in the treatment groups was evaluated based on C5a expression, oxidative stress, inflammation, and 2,3,5-triphenyltetrazolium chloride (TTC) staining of brain tissue.

Results: PET imaging studies found that ⁸⁹Zr-FNA were readily present in the cerebrospinal fluid (CSF) and brain 15 min p.i. The uptake of ⁸⁹Zr-aC5a-FNA slowly decreased and almost disappeared at 9 h p.i. Ex vivo PET imaging studies found no difference in the distribution of ⁸⁹Zr-FNA and ⁸⁹Zr-aC5a-FNA and that the biodistribution was consistent with the route of CSF circulation. aC5a-FNA was found to potent ROS scavengers and inhibitors C5a binding. Higher concentrations of C5a were found in the plasma and penumbra in PBS-treated IRI rats compared to those in the sham or aC5a-FNA. Levels of IL-1β and TNF-α in the PBS-treated group were much higher than those in the sham or aC5a-FNA groups. Compared to PBS or other controls, significantly fewer activated microglia and inflammatory cells were found in the ischemic penumbra with aC5a-FNA treatment. Compared with the sham groups, the PBS-treated group was found to have lower SOD and higher MDA levels due to oxidative stress from ischemic brain damage. However, treatment with aC5a-FNA recovered SOD and MDA levels similar to the sham group. TTC staining highlighted the increased infarct size and volume of PBS compared to sham or aC5a-FNA treated IRI rats. Conclusion: The high payload of an aptamer conjugated bipyramidal FNA was for cerebral IRI management was provided by intrathecal injection. This DNA framework alleviated the extent of cerebral IRI by acting as an antioxidant and inhibitor of inflammation.

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