Abstract
Purpose :
Intravitreal injection (IVI) is the only feasible method of drug delivery to the retina. However, IVIs are only suitable for drugs with large therapeutic indices and long half-lives, as rapid diffusion mediates clearance and loss of therapeutic effects. There is a need to improve IVI systems to reduce injection frequency and allow for delivery of drugs with unfavorable properties. Nanoparticle encapsulation of a drug can improve drug solubility, stability, and half-life. Exosomes are cell-derived vesicles that can be used as drug delivery nanoparticles. Hyaluronan is an aminoglycan found in high concentrations in the vitreous of the eye. Conjugation of hyaluronan-binding moieties is one strategy that can be used to restricting diffusion and improve the intravitreal half-life of therapeutics. The objectives are to design and evaluate hyaluronan-binding peptides using in silico modeling and in-vitro modeling. Then, peptides are evaluated for their ability to restrict exosomes drugs using an in vitro diffusion model. We hypothesize that presence of hyaluronan solution will decrease the diffusion rate of peptide conjugated exosomes, and thus may be useful for increasing the half-life of therapeutics for retinal drug delivery.
Methods :
Exosomes will be isolated from retinal cell culture using differential ultracentrifugation. Exosome cell uptake into retinal cells will be evaluated qualitatively by fluorescence microscopy. Drug loading and release will be evaluated following loading of exosomes with model small molecule drugs. Hyaluronan-binding peptides will be designed using molecular docking techniques. Candidate peptides will be conjugated to the surface of exosomes using click chemistry. Exosome diffusion rates will be evaluated using a diffusion cell model.
Results :
Exosomes were positive for CD63, had a mean diameter of 85.0 nm, and had round morphology as imaged by STEM. Molecular docking identified several peptides with strong interaction to hyaluronan. Exosomes displayed time depending uptake into ARPE19 cells in culture.
Conclusions :
Exosomes derived from retinal cell culture are a promising nanoparticles system for IVI as they have favorable properties for drug delivery. Molecular docking is a useful tool to design peptide ligands. Future work should evaluate the extent of drug loading and release and evaluate the effect of peptides on diffusion through hyaluronan solution.
This is a 2021 ARVO Annual Meeting abstract.