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Georgi A. Georgiev, Norihiko Yokoi, Slavyana Ivanova, Elena Kutsarova, Alexander Kyumurkov, Rumen Krastev, Zdravko Lalchev; Surface Chemistry Study of the Interactions of a Zinc Based Preservative System with Tear Film Constituents, Whole Tears and Corneal Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3727.
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© ARVO (1962-2015); The Authors (2016-present)
SofZiaTM (Alcon Laboratories, Inc., Ft. Worth, TX, USA), a zinc/borate/polyol preservative system (Z/B/P-PS), has reportedly been less harmful to the corneal epithelium and tear film (TF) in vivo and in vitro, as compared to benzalkonium chloride (BAC), the most common preservative used for eyedrops. A surface chemistry study was conducted to elucidate the interactions between the Z/B/P-PS having the same composition as sofZiaTM and TF constituents, whole tears and Statens Seruminstitut Rabbit Cornea (SIRC) cells.
The interactions between Z/B/P-PS and human meibum and whole tears, and SIRC cells lipid extracts at the air/water interface were examined in vitro at blink-like compression/expansion of film area by Langmuir surface balance, surface potential measurements, and axisymmetric drop shape analysis (PD-ADSA). The sample’s lateral elasticity and capability for compression and spreading during dynamic area changes were evaluated through the surface pressure-area isotherms and isocycles. The lipid film morphology was monitored by Brewster Angle Microscopy. The viability of Z/B/P-PS -treated SIRC cell cultures was examined. The results for Z/B/P-PS were compared to the effects of BAC in (sub)clinical concentrations (≤ 0.005%) on TF surface properties and cells viability.
The Langmuir monolayer and PD-ADSA experiments demonstrated the advantage of Z/B/P-PS to TF surface properties through the observation that, in the presence of Z/B/P-PS, the lipids and tears maintained the capability to spread and form continuous and thick viscoelastic multilayers with very low (≤ 3%) surface pressure-area hysteresis during compression/expansion. SIRC cells viability was completely preserved even after extended (> 5h) exposition to Z/B/P-PS solutions. In contrast, BAC impaired lipid film properties and SIRC viability within 10 sec after inclusion.
Z/B/P-PS is safe to the surface properties of TF and to SIRC cells viability and thus superior to BAC. A surface chemistry based approach is proposed for in vitro molecular scale discrimination between clinically used preservatives.
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