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Elaine Campbell, James W. Davis, Howard A. Ketelson, Michelle Senchyna; Characterization of an Experimental Lubricant Solution for Dry Eye. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3828.
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Polymers used in lubricant eye drops display significant physico-chemical differences especially when formulated in specific vehicles. Hydroxypropyl Guar (HPG) has been shown to provide lubrication on various substrates. This work summarizes the physical and biological attributes of an alternative guar polymer system (AGP) compared to HPG.
Physical properties were characterized by steady state flow (viscosity vs. shear rate) and oscillation (tan(Δ) vs stress) experiments using a TA2000ex rheometer The extensional properties were performed with a CaBER modified with a video monitor (3mm plate with Aspect Ratio of 4). The extensional properties were characterized with a Polymer Filament Break-up Time (PFBT) measured in seconds. Biological performance was measured as the ability to protect immortalized human corneal epithelial cells from damage initiated through exposure to desiccation stress. Cells were incubated with test solutions (AGP or HPG) or media (control) for 30 minutes, followed by 0 or 30min of desiccation at 37°; 45% humidity. To assess retention of cellular protection, a wash step was added between test compound exposure and desiccation. An MTS assay was used to determine % protection compared to control. Retention of cellular protection was also assessed.
AGP displayed a similar shear thinning effect and viscosity profile compared to HPG, with 40cPs and 14cPs respectively at 10sec-1. AGP displayed a significantly lower tan(Δ) compared to HPG; 6.1 vs 9.5 respectively at 1.0µNm (p< 0.05). The PFBT for AGP was significantly different to HPG (GT: 20sec vs 0.1 sec, respectively (p< 0.05)). AGP and HPG demonstrated a similar ability to protect cells from desiccation stress (40-60%), while retention associated with AGP was greater than that of HPG (90% vs 75%, respectively).
A novel AGP was identified that differs from HPG in both physico-chemical and biological attributes. The most relevant characteristics include improved viscoelasticity and longer PFBT that may correlate to improved desiccation protection and retention on the ocular surface, leading to improvement in ocular surface protection.
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