Drug delivery to the retina for the treatment of common retinal diseases including glaucoma, age-related macular degeneration and diabetic retinopathy remains challenging, especially for the emerging RNAi therapeutics. To achieve retinal targeting, intravitreally injected nanoparticles have been extensively employed as drug delivery carriers. The physicochemical properties of intravitreal nanoparticles significantly impact on their intraocular transport and retinal distribution, eventually the drug treatment efficacy. However, there is limited understanding of the correlation of the nanoparticle properties with their intraocular behaviors and drug delivery efficiency. To achieve targeted retinal drug delivery (such as siRNA) via engineered nanoparticles, this thesis has 3 aims: 1) inves...[ Read more ]

Drug delivery to the retina for the treatment of common retinal diseases including glaucoma, age-related macular degeneration and diabetic retinopathy remains challenging, especially for the emerging RNAi therapeutics. To achieve retinal targeting, intravitreally injected nanoparticles have been extensively employed as drug delivery carriers. The physicochemical properties of intravitreal nanoparticles significantly impact on their intraocular transport and retinal distribution, eventually the drug treatment efficacy. However, there is limited understanding of the correlation of the nanoparticle properties with their intraocular behaviors and drug delivery efficiency. To achieve targeted retinal drug delivery (such as siRNA) via engineered nanoparticles, this thesis has 3 aims: 1) investigating the charge impacts of intravitreal lipid nanoparticles (LNPs) on the intraocular transport and retinal distribution; 2) determining the gene silencing efficacy selectively by intravitreal charged LNPs among retinal layers; 3) developing ligand-modified LNPs for targeted delivery of siRNA to the retinal ganglion cells (RGC) in vivo.

Negative, neutral and mildly positive LNPs got rapidly eliminated from the eye within 6 hours after intravitreally injected. Positive LNPs ( zeta potential value: 30-40 mV) were found more optimal to distribute in the retina with a higher retina/vitreous partition compared to more positive LNPs (zeta potential value: 43-50 mV). LNPs with the optimal charge range (+33 mV) successfully delivered siRNA into the innermost retinal layers including the RGC layer and inner plexiform layer. Further in vivo functional studies showed that LNPs with optimal charge range (+30 mV) specifically suppressed 25% gene expression in the RGC layer. By keeping this optimal surface charge range, modification of ligand (IKRG) on LNPs significantly improved the in vitro siRNA delivery efficiency by 2 folds, compared to the non-modified LNPs. While in vivo studies showed that intravitreally injected IKRG-modified LNPs triggered retinal immune response and got dominantly internalized by activated microglia instead of targeting RGCs as designed. This adverse immune response was modulated through polymer coating, and high molecular weight HA exhibited inert in activating retinal microglia in vivo and suppressed microglia activation in vitro. In conclusion, this thesis identifies optimal surface charge range and potential targeting ligand for lipid nanoparticles to achieve targeted siRNA delivery to inner retina, especially RGCs, providing guidelines for engineering nanoparticles as potent delivery system to target the retina for the treatment of posterior ocular conditions.