Abstract
Purpose :
Local hotspots of elevated osmolarity of the tear film, predicted in the tear breakup domains, are implicated in dry eye disease (DED). We have prepared osmosensitive nanoliposomes and characterized for sensing local osmolarity of the tear film by noninvasive fluorescence imaging.
Methods :
Nanoliposomes, loaded with fluorescent dyes, calcein (susceptible to self-quenching) and sulforhodamine 101 (SR101), were produced by the thin-film hydration method followed by ultrasonication and repeated extrusion.
Results :
Nanoliposomes were spherical, unilamellar, uniform in size and negatively charged (117.9 ± 6.4 nm; polydispersity index [PDI] of 0.15 ± 0.02, -23.7 ± 1.5 mV). They showed negligible dye leakage during storage over 3 days, and underwent minimal changes in size, PDI, and charge. Deliberate swelling and shrinkage of nanoliposomes by exposure to hyposmotic and hyperosmotic media led to rapid de-quenching and quenching of calcein fluorescence. Thus, the ratio of green fluorescence of calcein (FGreen) to the red fluorescence of SR101 (FRed) decreased with increasing osmolarity and vice versa; FGreen/FRed vs. osmolarity obeyed Boyle-Van’t Hoff’s law. When nanoliposomes were dispersed in a gelatin film and sucrose solution was introduced at the center, local FGreen/FRed altered with osmolarity in response to sucrose gradients. When instilled on contact lenses or ex vivo porcine corneas, nanoliposomes suspension dispersed evenly and showed a decrease in FGreen/FRed vs. time when exposed to room air.
Conclusions :
Fluorescent nanoliposomes of high osmosensitivity and suitable for sensing local osmolarity on the corneal surface have been prepared and characterized. The measurements of local osmolarity will advance our current understanding of the pathophysiology of DED and possibly establish novel diagnostics to assess the severity of the disease.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.