Preferential renal uptake of DNA origami nanostructures protects mice from acute kidney injury

261 Objectives: Recent years saw the ever-increasing assembly of DNA nanostructures, especially a variety of DNA origami nanostructures (DNA origami, for short), for versatile applications such as nanomotors, nanocomputers, and bio-analysis. Researchers also envision the broad biomedical application of DNA origami in living animals due to its inherent biocompatibility. However, the intrinsic biodistribution and pharmacokinetics of DNA origami in animals has yet to be established. Herein, we apply positron emission tomography (PET) imaging to monitor the distribution of DNA origami, revealing its kidney targeting behavior in mice. Furthermore, we discovered the protection properties of DNA origami nanostructures for mice with acute kidney injury (AKI). Methods: Rectangular DNA origami (Rec-origami) was assembled by folding the M13 scaffold strand with sets of short synthetic oligonucleotides. Eight sidearms were designed on each DNA origami for hybridization of Cu-64 (half-life: 12.7 h) labeled single-stranded DNA (64Cu-NOTA-ssDNA) to form 64Cu-Rec-origami. Longitudinal PET imaging of 64Cu-Rec-origami was performed in both healthy and AKI mice for biodistribution studies and kidney targeting evaluation. AKI was induced by intramuscularly injecting 8 mL/kg of 50% glycerol to both hind limbs of the mice. Two hours after the AKI initiation, Rec-origami was intravenously injected for AKI therapy. PBS and unfolded M13 scaffold strand were used as negative controls, and N-acetyl cysteine (NAC) was applied as a positive control. The therapeutic effect was validated by 68Ga-EDTA dynamic PET, blood levels of creatinine and blood urea nitrogen, and kidney tissue staining. Results: PET imaging revealed that Rec-origami exhibited exclusive renal accumulation at 3 and 12 h after intravenous injection. M13, the unfolded counterpart of DNA origami, showed predominant liver uptake, indicating that only well-folded DNA origami can localize in the kidneys in vivo. Rec-origami was found therapeutically effective at the dose of 10 µg per mouse, as validated by dynamic PET imaging, serum tests, and kidney tissue staining. Most importantly, the treatment dose of Rec-origami was more than 400 times lower than that of NAC, which was about 4.2 mg per mouse. Conclusion: By using PET imaging, we were able to identify the renal targeting properties of DNA origami in both healthy and AKI mice. The localization of DNA origami in the kidneys may serve as protectants against AKI induced by 50% glycerol in vivo. Moreover, the applied dose of Rec-origami was more than 400 times lower than a commonly used antioxidant (NAC), suggesting the promising role of DNA origami nanostructures for kidney related diseases in the future.