Deposition of Fluorescently Tagged Lysozyme on Contact Lenses in a Physiological Blink Model

Abstract

Purpose: To visualize the deposition of fluorescein isothiocyanate (FITC) lysozyme on daily disposable contact lenses (CLs) using a novel blink model. Methods: Three daily disposable conventional hydrogel CLs (etafilcon A, omafilcon A, and nelfilcon A) and three silicone hydrogel CLs (delefilcon A, senofilcon A, and somofilcon A) were evaluated in the study. The CLs were mounted onto a novel blink model and exposed to an artificial tear solution containing FITC lysozyme for 2 and 10 hr. The flow rate and blink speed were set to 1 μL/min and 6 blinks/min, respectively. After the incubation period, a 5-mm-diameter disc was punched out from the center of the lens and mounted on a microscope slide. The slides were imaged using the Zeiss 510 Meta confocal laser scanning microscope, which scanned the lens from the front to the back surface at 5-μm increments. Results: There was an increase in deposition of FITC lysozyme for all lens types with increasing incubation time (P<0.05), with the exception of somofilcon A, which did not show statistical significance between 2 and 10 hr (P>0.05). The conventional hydrogel CLs deposited higher amounts of FITC lysozyme than the silicone hydrogel CLs (P<0.001), with etafilcon A depositing the highest at all time points (P<0.05). Interestingly, at the 2-hr incubation time, most CLs showed a higher amount of deposition at the front surface than the back surface of the lens. In particular, etafilcon A showed preferred deposition at the front surface at all time points. Conclusion: The results suggest that there is differential deposition at the front surface of the CL, which is exposed to the prelens tear film, compared with the back surface of the CL, which is exposed to the postlens tear film. Therefore, it may be beneficial to design CL materials with differing surface properties for the front and back surfaces of the CL to enhance interactions with the tear film and ocular surface.

Physical Properties and Interaction With the Ocular Surface of Water-Gradient Contact Lenses

“…Regarding the sorption localization, both labeled cholesterol and lysozyme permeated through the entire thickness of delefilcon A (SHy), despite the layered structure. 54,58 As discussed previously, hydration, wetting/dewetting properties, and shear stress during wear of WG-CLs are expected to be strongly affected by the morphology and composition of the outer layer, which depends on its interaction with tears. For example, tear mucins can adhere to the CLs in vivo and form a layer, which is desirable as long as CL-adherent mucins maintain their properties and do not trap debris or pathogens.…”

“…In this case, the outer layer of delefilcon A (SHy) affects the deposition of proteins onto the lens surface. 53,54 Nonetheless, these CLs often display a conventional SHy-CL behavior, as suggested by the interaction with lipophilic molecules. 58,59,69…”

“…Regarding the sorption localization, both labeled cholesterol and lysozyme permeated through the entire thickness of delefilcon A (SHy), despite the layered structure. 54,58…”

“…1,50 Recent studies focused on the deposition of lysozyme, which is a positively charged and abundant protein of the tear film, 51,52 evidenced that CL materials are affected by increasing lysozyme deposition with increasing incubation time. 53,54 Chan et al 53 measured lysozyme activity in an in vitro blink-simulation model and in a static vial deposition model on three Hy-CLs (etafilcon A, omafilcon A, nelfilcon A) and three SHy-CLs (delefilcon A, senofilcon A, somofilcon A) using an ATS containing lysozyme and other tear components. Phan et al 54 studied the same CLs with a blink-simulation model and employed fluorescently tagged lysozyme.…”

Contact Lens Wear Induces Alterations of Lactoferrin Functionality in Human Tears

“…Most of these studies make use of artificial tears solutions (ATSs), a simplified version of real tears containing several salts, lipids, and proteins. ATSs have the advantage to be simple, highly controlled, and reproducible samples for in vitro analyses, but represent only a rough model of the CLs–tears interaction [ 13 , 14 ].…”