Ocular drug delivery systems: An overview

Table 1 Summary of recent developments with nanoparticles as ocular drug delivery vehicles

Drug	Polymer	Features
Carboplatin	CH, SA	Carboplatin loaded NPs demonstrated elevated and sustained anti-proliferative activity in a retinoblastoma cell line (Y-79), with IC50 of 0.56 and 0.004 μg/mL for free carboplatin and carboplatin loaded NPs, respectively[49]
5-FU	CH, SA	CH coated SA-CH nanoparticles (CH-SA-CH NPs) loaded with 5-FU showed significantly higher concentration of 5-FU in aqueous humor as compared to SA-CH 5-FU loaded NPs and 5-FU solution. The higher Cmax was achieved in case of CH-SA-CH NPs (24.67 μg/mL) compared to 5-FU solution (6.14 μg/mL)[50]
Sparfloxacin	PLGA	After topical application, sparfloxacin-loaded nanoparticles were retained for a longer duration on the corneal surface as compared to an aqueous solution, which was drained rapidly from the corneal surface. Also, in vitro release studies revealed an extended release of sparfloxacin[51]
BT	Sodium alginate	BT-loaded nanoparticles provided prolong drug release over a period of 8 h after topical instillation to albino rabbits[52]
Levofloxacin	PLGA	The nanosuspensions was retained for the longer time on rabbit eye surface and drained out slowly compared to marketed formulation. Results of ex-vivo transcorneal permeation study across excised goat cornea revealed that levofloxacin from the marketed formulation was permeated 36.9% in 4 h whereas levofloxacin from PLGA nanoparticles was permeated 47.43% in 4 h across cornea[53]
DS	PLGA	An extended DS release was observed from the nanoparticles under in vitro conditions. The developed polymer nanoparticles formulation was non-irritant to cornea, iris, and conjunctiva for as long as 24 h after application[54]
Pilocarpine	PLGA	The in vivo miosis studies showed that the duration of miotic response increased by 40% for the nanoparticles compared to the eye drops[55]
Gatifloxacin/Prednisolone	Eudragit RS 100 and RL 100, coating with hyaluronic acid	In vitro release studies revealed prolonged drug release compared to the free drugs with no burst effect Nanoparticles formulation showed better bioavailability of gatifloxacin in rabbit eye with 1.76 fold increase in Cmax of gatifloxacin in the aqueous humor in comparison to the eye drops[56]
Cloricromene (AD6)	Eudragit	Nanosuspension enhanced stability of the ester drug for several months as compared to an AD6 aqueous solution[57]
Brimonidine Tartrate	Eudragit RS 100 Eudragit RL 100	The AUC (ΔIOP vs time) for the selected nanoparticles formulations were about seven times higher than that of eye drop formulations in rabbit eye[58]

CH: Chitosan; SA: Sodium alginate; 5-FU: 5-Fluorouracil; PLGA: Poly (lactide-co-glycolide); IOP: Intraocular pressure; AUC: Area under the curve; BT: Brimonidine tartrate; DS: Diclofenac sodium.