Summary of recent applications of hydrogels as conjunctival DDS
| Disease | Hydrogel composition | Delivery route & active ingredients | Study phase | Release duration | Advantages & limitations | Reference |
| Glaucoma | Chitosan; sodium alginate | Subconjunctival implant; inner core: timolol maleate; outermost layer: levofloxacin | In vitro; in vivo (rabbits) | Levofloxacin: 9 days; timolol maleate: up to 17 days | Photothermal effect: release more drugs upon irradiation; multidrug delivery system with structures that resemble the different layers of a lollipop; cause eye discomfort after long-term use; long-term toxicity needs to be investigated | [64] |
| Hyaluronic acid | Thin films in the conjunctival sac; timolol | In vitro; ex vivo (pigs) | Over 24 hours | Direct loading of drug into HA-based matrices; drug availability across the entire film surface; lack of in vivo experiments | [65] | |
| Corneal alkali burn | PLGA-PEG-PLGA triblock polymer | Subconjunctival injection; adalimumab; aflibercept | In vitro; in vivo | 3 months | Thermosensitive; complete inhibition of corneal neovascularization; increased protection of the retina and optic nerve; minimal systemic exposure; the extent to which the drug delivery system affects therapeutic outcomes of TNF-α/VEGF inhibition is not clear | [66] |
DDS: drug delivery systems; HA: hyaluronic acid; PLGA-PEG-PLGA: poly(lactic-co-glycolic acid)-poly(ethylene glycol)-poly(lactic-co-glycolic acid); TNF-α/VEGF: tumor necrosis factor alpha/vascular endothelial growth factor