Novel mucoadhesive polysaccharide isolated from Bletilla striata improves the intraocular penetration and efficacy of levofloxacin in the topical treatment of experimental bacterial keratitis

Objectives The objective of the present study was to evaluate a novel mucoadhesive polymer extracted from Bletilla striata for ocular delivery of 0.5% levofloxacin in rabbits, and to determine its improved efficacy against experimental keratitis. Methods B. striata polysaccharide (BsP) was subjected to cell cytotoxicity and ferning tests. The pharmacokinetics and bioavailability of topically applied 0.5% levofloxacin-BsP eye drops was investigated and compared with 0.5% levofloxacin eye drops (Cravit). Experimental Staphylococcus aureus keratitis was induced and treated with levofloxacin or levofloxacin-BsP eye drops. Key findings BsP markedly increased the proliferative capacity of a human corneal endothelial cell line. The ferning test showed that BsP exhibited optimal performance as a tear fluid. The polysaccharides significantly increased intra-aqueous penetration and corneal accumulation in rabbits. Treatment with levofloxacin-BsP reduced the number of organisms more significantly than eye drops containing levofloxacin alone. Conclusions BsP appears to be a promising candidate as a vehicle for topical ophthalmic drug delivery, especially for antibiotics.