Injectable oxygen carriers for the treatment of retinal ischemia

Abstract

Purpose : To develop an oxygen-based nanodelivery system consisting of oxygen nanobubbles (ONBs) to revert an ischemic insult in the inner retina during central retinal artery occlusion (CRAO).

Methods : ONBs were synthesized via sonication to create a dextran-based shell, where the components of the shell are held together via electrostatic interactions to encapsulate O₂ saturated medical grade water. The conceptualized ONBs were tested for their O₂ release kinetics at different pH and temperature. Additionally, reactive oxygen species (ROS), double stranded DNA (dsDNA) damage, and cell viability in hypoxic and normoxic environments were evaluated. Mitochondrial health was evaluated via Mitochondria Stress test in hypoxia. Lastly, a pilot safety experiment was conducted in rabbits and efficacy evaluated in an ischemia-reperfusion (I/R) rat model.

Results : The ONBs were 218.71±51.05nm in diameter with a surface charge of -58.8±1.3 mV. Based on the O₂ release profile, an estimated 74.06µg of O₂ was released from the ONBs after 12h at 37°C. Cell studies in Muller and R28 cells showed successful uptake of ONBs and no significant increase in ROS, super oxide, or dsDNA damage compared to the negative control. The ONBs were able to successfully preserve mitochondria health and function in both the Muller and R28 cells after 6h of exposure to hypoxia. Last, there were no detected toxic effects of the ONBs after 3 days post intravitreal injection into New Zealand white rabbits. Efficacy tests with the I/R rat models indicated that the ONBs were able to revive the retinal cell layers and retinal function (ERG).

Conclusions : Our work demonstrates that ONBs could be a potential treatment option for treating ischemic conditions in the retina, such as CRAO, among others.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

A)Change in O₂ conc upon release in hypoxic system. n=3. Inset: TEM of dextran ONBs. B) Muller and R28 cell viability after 6h in hypoxia (5% O₂) with treatment of ONBs, Shell (no O₂), or NT. n=8. C) Mitochondria maximal respiration of R28 and Muller cells after 6h of hypoxia with of ONBs or Shell. n=8. D) Change in IOP of rabbit eyes after injection of Saline or ONBs. n=6. E) Typical images of rabbit retinas 7 days post injection. Rabbits intravitreally injected with saline or ONBs. Scale bar=20μm. Images at 40x. NT: No Treatment. Data shown as mean±standard deviation. †Significant difference to NT Normoxia. ‡Significant difference to NT Hypoxia. ****p<0.00001, ***p<0.0001,**p<0.001.