Table 1.

Overview of the characteristics and advantages of biopolymers.

Biopolymer	Characteristics	Advantages
Hyaluronic Acid	Anionic polymer and high water-retention capacity.	Can be used in hydrogel formulations. Prolonged tear film stabilization. Can coat liposomes to elongate drug release and increase cellular uptake.
Cellulose	Can self-assemble into nanorods, nanospheres, nanosponges, and nanorods upon functionalization with a copolymer, allowing for ease of bulk manufacturing.	Used in conventional eye drops to improve viscosity. Different derivatives are extensively applied in ocular drug delivery. HPMC swells in contact with water, forming hydrogels with mucoadhesive properties.
Chitosan	Requires chemical modification, is mucoadhesive, and has unique in situ gelling properties.	Excellent corneal permeation. Can temporarily open tight junctions to increase drug permeability. Can increase antibacterial activity when functionalized with quaternary ammoniums.
Alginate	Anionic copolymer that can exert cell immobilization and can be used in copolymeric nanoparticles with chitosan derivatives.	Suitable polymer in hydrogels. Terminable hydrogels due to reversible gelation.
PLGA	Commonly used, subject to abundant modifications, can be enhanced in size and surface potential, and can be modified with PEG.	Sustained drug release. High entrapment efficiency. Topical administration can deliver drugs to the posterior segment of the eye.
Poloxamers	Biodegradable, mucomimetic, and non-ionic surfactants.	Approved by the FDA as a vehicle for ocular drug delivery. Used in various ocular formulations.
Cyclodextrins	Cyclic oligosaccharides can form hydrophobic cavities with externally hydrophilic surfaces.	Can increase the bioavailability of many guests. Wide range of formulations with great potential for ocular drug delivery.

FDA: Food and Drug Administration. PEG: Poly(ethylene glycol). PLGA: Poly(lactide-co-glycolide).