Enzyme-functionalized microparticles to open the vitreoretinal interface

The transport of therapeutics and gene carriers to their site of action is often hindered by biological barriers, such as cell layers and basement membranes. Among these, the inner limiting membrane (ILM) represents a major barrier within the eye, separating the vitreous body from the retina. The ILM must be crossed, if for instance gene carriers are to reach retinal target cells following intravitreal administration. However, the ILM is a densely cross-linked basement membrane barrier, allowing only the smallest nanoparticles to pass. Here, we demonstrate that active micro-colloids decorated with enzymes can locally open the ILM and thereby facilitate the diffusion of passive carriers into retinal tissue. We utilize an ex vivo porcine eye model to determine the membrane permeability threshold using fluorescent nanoprobes. We further show that collagenase-decorated silica microparticles can facilitate the transport of nanoparticles, while exhibiting excellent biocompatibility with no adverse morphological or functional retinal effects over a six-week in vivo evaluation in a porcine model. Overall, our findings introduce a biocompatible and minimally invasive strategy to facilitate the targeted nanoparticle transport across biological barriers, which we demonstrate for retinal delivery enabled by active colloids.