Ophthalmic Properties of Targeted Fusogenic Nanoparticles as Therapeutic Carriers

Abstract

Purpose : Intraocular drug delivery faces many challenges including delivery of drugs for extended periods to targeted tissues without adverse systemic effects. Currently, free drug is injected into the vitreous cavity every four to eight weeks with initial overdosing of tissues. In addition, most current therapeutics simply bind pathogenic molecules but do not stop their production. The ability to deliver RNA interference therapeutics intracellularly via a cell receptor specific targeting approach would solve many of the problems of intravitreal therapy.

Methods : We synthesized siRNA carriers consisting of porous silicon nanoparticles that are incorporated into fusogenic liposomes by film hydration to deliver the nanoparticles intracellularly (Fig. 1). The iRGD targeting peptide (CRGDKGPDC), developed to deliver anticancer therapeutics to malignant tumors, was conjugated to the liposome surface and is specific for neovascular epithelium. DL-α-aminoadipic acid (DL-AAA) was used to induce retinal neovascularization (RNV) in rabbits to evaluate the ability of the targeted fusogenic nanoparticles (TFNP) loaded with VEGF siRNA to reduce vascular growth. Normal rabbit eyes were dosed intravitreally with TFNP loaded with 10 μg VEGF siRNA in a 50 μL volume. Toxicologic and optical evaluations included slit lamp, fundus, optical coherence tomography, and fluorescein angiography at 2 and 8 weeks.

Results : The vitreous cavity remained clear and all evaluations including histology and electroretinography showed no evidence of toxicity. Fluorescein leakage in the RNV model was absent in eyes treated with VEGF siRNA loaded TFNPs compared to control eyes at 8 weeks (Fig. 2).

Conclusions : TFNPs are a novel and safe vehicle to deliver RNA therapeutics intracellularly. The porous silicon nanoparticles load high quantities of the nucleic acid payload, and the fusogenic lipid coatings enable cell entry while avoiding endocytosis. Targeting of cell-surface receptors expressed more extensively during specific disease allows more accurate targeting of diseased tissues and permits longer acting effects from a single intravitreal injection.

This is a 2021 ARVO Annual Meeting abstract.

 

Schematic of fusogenic nanoparticle synthesis and mechanisms of targeted cellular uptake.

 

Fluorescein angiography of DL-AAA injected eyes at 2 weeks, just prior to TFNP treatment, and again at 8 weeks. OD top row received TFNPs, and bottom row sham treatment. OS received no injections.