Influence of tear fluid properties on physicochemical, mucoadhesion and ocular penetration characteristics of transfersomes.

Due to changes in the tear fluid properties in dry eye disease (DED), eye drop performance may be altered. This study investigated the impact of tear fluid properties on the physicochemical, mucoadhesion and ocular penetration characteristics of transfersome (TFS) eye drops. Specifically, the effect of tear fluid pH and osmolarity on vesicle size, polydispersibility index (PDI) and zeta potential (ZP) of unloaded as well as curcumin- and tonabersat-loaded TFS were studied. Finally, the effect of altered tear fluid properties on corneal penetration of curcumin TFS was investigated using ex vivo porcine corneo-scleral discs. A significant increase in vesicle size and PDI was observed for curcumin and tonabersat TFS suspended in healthy and DED tears compared to water. Moreover, the ZP measured in water shifted towards neutral in the case of healthy and DED tears, suggesting reduced electrostatic stability of the vesicles. Deeper tissue penetration was observed for curcumin TFS suspended in water compared to TFS suspended in healthy tears, with significantly less penetration for TFS mixed with DED tears. This study confirmed that tear fluid properties significantly influence TFS characteristics and thus their penetration ability, highlighting the importance of evaluating ocular drug delivery systems under physiological conditions that reflect the disease state.