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M. Mazzone, Sr., O. Peri, V. Moschetti; Evaluation of Mucoadhesive Properties of Xanthan Gum Hydrogels versus Marketed Ophthalmic Gel Formulations Using a Tensile Strength Method . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1966.
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The aim of this study was to compare in vitro mucoadhesive performance of marketed ophthalmic gels (Dacriogel single– and multi–dose, Lacrigel, Lacrinorm, Dropgel, SiccaFluid, Genteal, Viscotirs), versus a new line of xanthan gum based hydrogels (XG), formulated in a balanced salt solution.
The mucoadhesion performance was assessed by using a tensile strength test (Texture Analyzer TA–XT2, Stable Micro Systems, UK), equipped with an upper movable cylindrical probe and a lower cylinder fixed to the platform. A 4% w/w mucin (Sigma, type II) dispersion was used as a mucus substitute. Instrumental parameters were set (velocity, contact time, contact depth, etc.) in order to obtain results such as the failure force (F), the deformation to failure (D) and the work (W) necessary to achieve the break of the bonds at the weakest region of the tested system: formulation–formulation (Fform; Dform; Wform or cohesiveness) mucin–mucin (Wmuc), and mucin–formulation (Wmucoad or adhesion).
For all tested gels, Wform was significantly higher than Wmuc (P<0,05). Therefore, when Wmucoad > Wmuc, it means that a formulation–mucin interaction occurs. Among the tested formulations, XG showed the strongest mucoadhesion, followed by single–dose Dacriogel and Lacrigel (Wmucoad > Wmuc; P<0,001). All other formulations didn’t show a significant interaction with mucin. Moreover, we found that XG formulations, and Lacrigel showed a low Wform and Fform, and high Dform values, indicating a low degree of hardness, and a high degree of elasticity.
The tensile test is a sensitive, simple method to investigate not only the mechanical properties of gel formulations, such as mucoadhesion and elasticity, but also the effect of additives (e.g. preservatives) on the behaviour of the dosage form. All XG formulations show a stronger mucoadhesion and elasticity than the carbomer–based gel formulations. This is predictive of a good compliance of XG after ophthalmic administration (i.e. prolonged contact time, no blurry vision and good spreadability).
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