The effects of PEGylation on LNP based mRNA delivery to the eye

Gene therapy is now an effective approach to treat many forms of retinal degeneration. Delivery agents that are cell-specific, allow for multiple dosing regimens, and have low immunogenicity are needed to expand the utility of gene therapy for the retina. We generated eight novel lipid nanoparticles (LNPs) ranging in size from 50 nm to 150 nm by changing the PEG content from 5% to 0.5%, respectively. Subretinal injections of LNP-mRNA encoding luciferase revealed that 0.5% PEG content within nanoparticles elicits the highest expression. Similar injections of LNP delivered cre mRNA into Ai9 mice revealed cell-specific protein expression in the retinal pigment epithelium (RPE), confirmed by fundus photography and immunohistochemistry of whole globe cross-sections. To investigate mechanisms of LNP delivery to the eye, we injected mCherry mRNA using the subretinal approach in apoE^-/- and Mertk^-/- mice. RPE transfection was observed in both mouse models suggesting that LNP intracellular delivery is not solely dependent on apolipoprotein adsorption or phagocytosis. To investigate LNP penetration, particles were delivered to the vitreous chamber via an intravitreal injection. The 0.5% PEG particles mediated the highest luciferase activity and expression was observed in the Müller glia, the optic nerve head and the trabecular meshwork, but failed to reach the RPE. Overall, particles containing less PEG (~150 nm in size) mediated the highest expression in the eye. Thus far, these particles successfully transfect RPE, Müller cells, the optic nerve head and the trabecular meshwork based on route of administration which can expand the utility of LNP-mediated gene therapies for the eye.