Ex vivo bovine retinal models to study intravitreal mobility and inner limiting membrane penetration of nanomedicines

Abstract

AbstractSeveral viral and non‐viral nanoparticles aim to deliver therapeutics such as proteins or nucleic acids to the back of the eye, to halt or slow down retinal cell death. To reach the retinal cell types, intravitreal or subretinal injections are performed. Intravitreal (IVT) injection delivers the therapeutics into the vitreous, from where they need to diffuse to the back of the eye and cross the Inner Limiting Membrane (ILM) to reach the retinal cells. IVT injected therapeutics and nanoparticles might suffer, however, from a limited mobility and penetration through the vitreoretinal (VR) interface (e.g. vitreous and ILM), hampering their efficiency. We recently developed two ex vivo bovine eye models that are suitable to study the barrier role of the vitreoretinal interface. The IVT Mobility Model allows to measure the mobility of fluorescent nanoparticles in intact vitreous on a single‐particle level by tracking their movement by fluorescent Single Particle Tracking. In the VR explant Model, penetration over the ILM is studied in a bovine ex vivo retinal explant with the vitreous still attached. In regular ex vivo explants, the removal of vitreous distorts the ILM, making the explant unsuited for penetration studies. With the VR explant, however, the crossing of IVT injected material over the intact ILM and the penetration depth into retinal cell layers can be determined. Both models were applied to study the potential of intravitreal injected mRNA lipoplexes, where we found good mobility in the vitreous but limited crossing of the ILM after IVT injection. This most likely explains the low in vivo expression obtained after IVT injection of mRNA nanoparticles in mice, while expression was found in vivo after subretinal injection.