Abstract
Purpose: :
To study the physico-chemical properties of a novel artificial tear emulsion product technology based on an anionic phospholipid, mineral oil, HP-Guar and the demulcent propylene glycol. Adhesion, spreading pressures, steady state flow rheology and friction measurements were used to evaluate the emulsions for use as a restorative tear replacement eye drop displaying ocular surface protectant benefits.
Methods: :
The emulsions were formed using mineral oil and a novel blend of interfacial substances with processing via in-line homogenization. Emulsions were adjusted to pH’s between 7-8. Adhesion and spreading experiments were evaluated by Langmuir Trough, elipsometry and light microscopy. Steady state flow and dynamic rheology profiles were obtained using a controlled state rheometer. Friction coefficients were measured using a pin-on-disc tribometer with pericardium tissue as the substrate.
Results: :
Contact angle measurements indicated that the liquid/vapor surface tensions of the emulsions varied between approximately 70 mNm-1 at pH 7 to 56 mNm-1 at pH 8. The maximum estimated spreading pressures for the o/w emulsion were between 6-8 mNm-1. The emulsions at elevated pH (>7.4) displayed thixotropic behavior. For example, steady state flow experiments on emulsions at pH’s > 7.4 showed that that the viscosity decreased from 146 cps to 4.6 cps as the shear rate increased from 0.01s-1 to 1s-1, respectively. The emulsions also showed significant reductions in their coefficients of friction. For example, the friction coefficients for the emulsions were less than 0.1 for pH’s greater than 7.4.
Conclusions: :
The data showed that a stable oil-water emulsion containing HP-Guar, an anionic phospholipid and a demulcent can be generated as a novel artificial tear product. The artificial tear product has a novel composition blend to provide ocular surface protectant properties.
Keywords: cornea: tears/tear film/dry eye