Table 3.

Polymers used for preparing polymeric nanoparticles and their potential applications in retinal diseases.

Polymers	Method of the Preparation	Characterization	Applications	Refs.
N-isopropylacrylamide and acrylamide	Radical polymerization	A preventive treatment for retinal degeneration using neuroprotective polymeric nanoparticulate systems was explored. The nanoparticles showed a size distribution of 22.81 ± 3.17 nm.	The formulation was injected intravitreally into the left eye of zebrafish embryos. The formulation increased the residence time over the cornea, resulting in a neuroprotective response against oxidative stress in both in vitro and in vivo studies.	[108]
PLGA-PEG	Double emulsion solvent evaporation	Memantine-loaded PLGA-PEG nanoparticles were formulated to prevent retinal ganglion cell (RGC) loss. The drug-loaded nanoparticles showed a mean particle diameter of <200 nm.	The formulation was used as a topical administration (eye drops) in a rodent model. The formulation was neuroprotective in an ocular hypertension rodent model by significantly conserving the RGC density.	[109]
Chitosan-coated PLGA	Oil-in-water emulsion	A topical formulation was developed by loading triamcinolone acetonide into chitosan-coated PLGA nanoparticles for treating retinal vasculopathy. Nanoparticles were obtained with a particle diameter of 334 ± 67 to 386 ± 15 nm.	The formulation was developed as a topical administration. The formulation showed controlled drug release and no toxicity to the ocular surface.	[110]
Chitosan functionalized PLGA	Nanoprecipitation	Sirolimus drug was loaded into nanoparticles with a mean particle size of 265.9 ± 6.3 nm.	The Sirolimus-loaded nanoparticles were administered via subconjunctival injection. Over 21 days, sirolimus-loaded nanoparticles prevented apoptosis in the damaged retina.	[111]
Bovine serum albumin, hyaluronic acid.	Desolvation	Apatinib-loaded nanoparticles were topically administered to treat diabetic retinopathy. The drug-loaded nanoparticles had a mean size of 222.2 ± 3.56 nm.	The formulation was developed as a topical administration, and efficacy was evaluated in a diabetic rat model. The retinal thickness significantly declined after nanoparticle treatment compared to the control group in the diabetic retinopathy-induced rat model.	[112]
PLGA-hyaluronic acid	Solvent displacement	Itraconazole-loaded PLGA-HA nanoparticles were conjugated with R5K peptide for treating AMD. The drug-loaded nanoparticles displayed a particle size of 167.5 to 217.0 nm.	The formulation was developed as an intravitreal injection to improve the bioavailability of anti-VEGF drugs. Conjugating the R5K peptide to the drug-loaded PLGA-HA significantly improved the binding affinity of VEGF molecules. With the synergetic effect of Itraconazole, the nanoparticles enhanced the treatment efficacy.	[113]
Polydopamine	Classical Stober method	Brimonidine-loaded polydopamine nanoparticles were prepared to decrease optic nerve crush-induced RGC apoptosis. The polydopamine nanoparticles showed a hydrodynamic size of 215 ± 2.6 nm.	The formulation was injected intravitreally into the mice using a Hamilton syringe. A single dose of nanoparticles via intravitreal injection was able to eliminate ROS in the retina and improve neurodegeneration.	[114]
Thiolated and methylated chitosan carboxymethyl dextran	Coacervation	A novel delivery system was developed to deliver drugs to the posterior eye segment in a retinoblastoma-induced rat model. The formulations displayed a particle size of 34–42 nm.	The formulation was injected intravitreally into the eyes of rats with retinoblastoma. The nanoparticles were able to reach the retina through diffusion after intravitreal injection.	[115]