(673e) Protein Release from Contact Lenses Monitored By Interfacial Viscoelasticity

Contact lenses are the most prescribed biomaterial with over 125 million wearers who are often plagued by deposition of proteins and lipids in the eye [1]. Protein adsorption, especially denatured protein, increases the risk of microbial cell attachment to the lens and inflammatory diseases such as giant papillary conjunctivitis; their effect on tear film stability have yet to be studied [2]. This study demonstrates the use of an optical platform to monitor drainage of fluid on contact lenses, interfacial rheology, and two-photon microscopy to analyze both the uptake and release of lysozyme in contact lenses. Lysozyme was chosen as the protein of interest here because of its high concentration in the tear film (20-30% of the total tear film protein), relatively small size, and high isoelectric point (11.4), making it positively charged in the tear film (pH 7.4) [2]. Our research aims to understand how lysozyme deposition and desorption affects interfacial properties of a fluid-air interface for conventional and silicone hydrogel contact lenses, which is of importance for a stable tear film.

We found that after exposure to lysozyme, a conventional hydrogel (1 Day Acuvue, Johnson & Johnson) and a silicone hydrogel (Acuvue Oasys, Johnson & Johnson) have markedly different thin film stability profiles, as evidenced by the critical film thickness for breakup in phosphate-buffered saline drainage experiments. This change in film stability can be attributed to the elevation in interfacial rheology during lysozyme desorption from lenses. While the bulk rheology did not significantly change during lysozyme desorption, and surface pressure measurements were not sensitive to protein network formation at the interface, interfacial rheology measurements were consistent with the thin film stability observed in experiments. In tandem with thin film drainage measurements, interfacial rheology can be used to determine the effects of other protein and lipid deposits on tear film stability and, fundamentally, the effects of individual tear film components on tear film stability.

References

[1] J. E. Key. Eye Contact Lens. 33, 343 (2007).

[2] D. Luensmann, et al., Cont Lens Anterior Eye. 35,53 (2012).

[3] L. N. Subbaraman, L. Jones. J Biomed Sci Polym. 21, 343 (2010).