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Trust Razunguzwa, Haddon Goodman, CHENG-CHUN PENG, Neil Fajardo, Clayton Radke; In-Vitro Spoilation of SiHy Soft Contact Lenses using LAESI-MS and FCSLM. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5488.
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© ARVO (1962-2015); The Authors (2016-present)
We utilize an in vitro blink cell to study the mechanism(s) of white-spot (i.e., jelly-bump) formation of fouled contact lens based on direct contact of meibum lipid with the lens on eye upon pre-lens tear film rupture. To provide insight into lens spoilation, the spatial distribution and composition of the spot deposits was determined by Laser Ablation Electrospray Ionization Mass Spectrometry (LAESI-MS) for proteins and Fluorescence Confocal Scanning Laser Microscopy (FCSLM) for lipids.
An SiHy SCL (ACUVUE® ADVANCE) was attached to a Teflon mold and immersed in artificial tear solution with protein, salts and mucins (ATS). Artifical lipid (AL) was spread over the air/water interface to form a lipid layer. To form fouled deposits on the lens that replicate the in-vivo process, the ATS film between the lens and the lipid layer was periodically ruptured and reformed by withdrawing and then injecting aqueous solution into the cell mimicking the blink process. Deposits were analyzed by optical microscopy, LAESI®-MS, and FCSLM.
Discrete deposition spots with average size of 20~300 μm were observed by optical microscopy (Fig 1A) confirming what is seen in-vivo and validating the in-vitro blink cell. By using fluorescein-tagged lipid, lipid deposits on the lens surface were identified by two-photon FCSLM (Fig. 2B). The 2D mapping over the lens surface by LAESI®-MS detects protein deposits (Fig 2C). Both the lipid and protein 2D surface maps overlap with the white spots seen by optical microscopy. By z-scanning, we also observe lipid and protein penetration into the SiHy lens.
In vitro spoilation of SCLs is successfully achieved by an in-vitro blink cell that now provides a reliable screen for new antifouling lens materials, surface coatings, and care solutions. New techniques for 2D surface analysis, i.e., LAESI®-MS and FCSLM, give the composition of the fouled deposits and allow understanding of the mechanism(s) of fouling. For ACUVUE® ADVANCE lenses, lipids and proteins not only deposit on the lens surface, but also penetrate into the bulk lens, likely due to the bi-continuous microstructure of silicone and hydrophilic polymer phases of the lens.
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