Strategic lipid nanoparticle design dictates retinal delivery post inner limiting membrane disruption

The interest in lipid nanoparticle (LNP)-mediated mRNA delivery significantly accelerated in the aftermath of the clinical success of mRNA-based COVID-19 vaccines. Validated as an effective and scalable platform, LNPs are now considered a cornerstone technology for the development of next-generation nucleic acid therapeutics. Recently, mRNA therapy entered the field of retinal gene therapy where it could treat retinal disorders contributing to the global numbers of vision impairment and blindness. While an historically driven focus on targeting outer retinal cells was initially in place, a shift toward delivery to the inner retina via intravitreal injection is ongoing. Yet, successful delivery is cumbersome since many nanocarriers are trapped at the inner limiting membrane (ILM). Therefore, this study enlightens the role of the ILM barrier with due consideration how fine-tuning LNP design impacts delivery after ILM disruption. For a standard LNP composition, we showed that ILM disruption is resulting in remarkable amounts of mRNA expression as opposed to an intact ILM. Based on an in-depth in vitro screening, the standard DSPC helper lipid was switched to DOPE to enhance expression levels and the percentage of PEGylation was adjusted to define LNP size. Despite the negative impact of elevated PEGylation on transfection efficiency in vitro, a significant boost in transfected retinal cells was noticed in an ex vivo setting due to improved penetration in the retina. In conclusion, we demonstrated that strategic design of LNP composition can boost LNP delivery beyond the ILM barrier and drive mRNA-LNP therapy to the retina forward.