The management of ocular infections is challenging due to poor drug bioavailability and vehicle related adverse effects associated with current antibiotic eye drops. Semifluorinated alkanes (SFAs) are reportedly well-tolerated on the ocular surface and can enhance ocular drug bioavailability. Therefore, an SFA-based azithromycin suspension (SFA-AZM) was prepared and its antibacterial efficacy was compared to that of marketed azithromycin eye drops by monitoring the growth of bioluminescent Staphylococcus aureus in ex vivo ocular tissues. Corneal and conjunctival distribution of hydrophobic fluorescent dye particles from an SFA suspension (SFA-BODIPY) resulted in preferential dye localisation in the epithelial layers of both tissues. However, corneal dye absorption was significantly lower than conjunctival absorption, likely due to limited adhesion of suspended dye particles to the corneal compared to the conjunctival epithelium. In line with the dye distribution results, bacterial colonisation in the conjunctiva reduced significantly upon application of SFA-AZM with the efficacy being greater than or at least equal to the marketed azithromycin eye drops. In the cornea, all tested azithromycin eye drops reduced the rate of bacterial growth with similar efficacy. Overall, the SFA-AZM suspension tested here may provide a safe and effective alternative for the management of ocular infections by enhancing conjunctival drug absorption and thus drug efficacy.
Keywords: Antibiotic eye drop; Azithromycin; Bioluminescent bacteria; Ex vivo study; Ocular drug delivery; Semifluorinated alkanes; Staphylococcus aureus.
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