Purchase this article with an account.
Robert H. Pelton, Yuguo Cui, Liang Zhang, Howard A. Ketelson, James W. Davis, David L. Meadows; Enhancement of Lipid Stability in the Eye by Polymer Depletion Interactions. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3738.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The goal was to determine if high molecular weight water-soluble polymers, added to eye drops to increase viscosity and decrease friction, have the potential to induce aggregation of emulsified oils or lipids both on the shelf and on the eye, by a mechanism called depletion flocculation.
Uniform cationic liposomes based on 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were prepared with an average particle size of 100 nm. Hydroxypropyl guar (HPG) with a MW 1.5 MDa solutions were added to the liposome suspension under conditions of controlled pH, ionic strength and temperature. The colloidal stability of the liposomes was monitored by dynamic light scattering and turbidity measurements.
Addition of HPG (MW 1.5 MDa) to a dispersion of DOTAP liposomes induced aggregation of the dispersed lipid particles when the HPG concentration was greater than about 0.1 g/L even though HPG does not bind to liposomes. The minimum polymer concentration required to induce flocculation increased by an order of magnitude when the HPG molecular weight was lowered to 0.01MDa.
HPG and other high molecular weight water-water soluble polymers can induce the aggregation of oil-in-water emulsions even when the polymer does not bind to the emulsion droplets. At the polymer concentration where the viscosity starts to increase, competition for free water drives the emulsion droplets together by a process called depletion flocculation. We propose that depletion forces also contribute to the stabilization the lipid layer by providing a barrier to lipid emulsification.
This PDF is available to Subscribers Only