Abstract
Purpose: :
The purpose of this study was to develop systemically administered, nanoparticulate, targeted retinal gene delivery systems. Specifically, transferrin, a linear RGD peptide, or dual labeled, VEGF intraceptor (Flt23K) plasmid loaded poly-(lactide-co-glycolide) (PLGA) nanoparticles were engineered to target CNV lesions upon intravenous administration.
Methods: :
Animal studies were conducted as per ARVO and UNMC IACUC guidelines. CNV was induced in Brown Norway rats (adult, male) using a 532 nm laser in the right eye. Eight laser cauterizations (100 µm, 150 mW, 0.1 sec) were performed per eye around the optic nerve. On day 14 post laser treatment, rats were administered nanoparticles or vehicle (control) intravenously. All nanoparticles contained nile red as a marker for tracking nanoparticles. In plasmid loaded nanoparticles, GFP expression from the VEGF intraceptor plasmid was used to track gene expression. Besides controls (NP), four plasmid loaded nanoparticles were used: unconjugated (Flt23K-NP), transferrin conjugated (Tf-Flt23K-NP), RGD peptide conjugated (RGD-Flt23K-NP), RGD peptide and transferrin conjugated (RGD-Tf-Flt23K-NP). Flat mounts and frozen sections were prepared 24 and 48 h post nanoparticle injection, respectively, and examined by confocal microscopy.
Results: :
In all the flat mounts, nanoparticles were detected in the laser treated (ipsilateral) eye, but not in the control (contralateral) eye. At 24 h, retinal delivery of all targeted nanoparticles was higher as compared to non-targeted nanoparticles. Further, dual label and RGD peptide, but not transferrin alone, clearly targeted the gene to retinal blood vessels of the ipsilateral eye. However, no gene expression was evident with non-targeted nanoparticles. At 48 h, in frozen sections, transferrin, RGD, and dual targeted nanoparticles showed GFP expression in photoreceptors as well as RPE cells, while non-functionalized nanoparticles showed expression only in photoreceptor inner segments.
Conclusions: :
Functionalized nanoparticles allow targeted, rapid gene delivery to neovascular lesions upon systemic administration for the management of age related macular degeneration. Targeted delivery of antiangiogenic genes to VEGF secreting retinal pigment epithelial cells can be tuned by changing the targeting ligand.
Keywords: age-related macular degeneration • choroid: neovascularization • gene transfer/gene therapy