Surface Tensiometry in Pharmaceutical Technology: Recent Progress in the Application of the Solid-Like Methodology Using the Contact Angle Method

The Solid-like Methodology was used to determine the surface tension of liquids using a liquid film of perfluoropolyether as a solid substrate. The contact between the liquid and the liquid film produces a deformation whose value depends on the nature of the liquid investigated. The value of the deformation is determined using the contact angle method by which it is possible to calculate the Rossi number, a pure number that characterizes the surface tension of the liquid tested without the influence of friction force and surface roughness. Our work introduces a new surface tensiometry method for perfluoropolyether-based materials called the "Wells Methodology" based on the interfacial phenomena occurring between a finite volume of perfluoropolyether and the drop of a liquid. The integration of the surface tensiometry data and data relating to the structures and release profiles of semi-solid formulations has demonstrated the relationship between surface free energy and the concentrations of the drug released over time. The variations in drug concentration reflect in Rossi number values of the acceptor solution (acceptor phase). The acceptor solution is the liquid phase in which the released drug from the formulation is solubilized. The surface tensiometry technique has demonstrated the importance of this non-invasive, rapid, and economical approach for the characterization of complex systems in the pharmaceutical technology field because of the importance of the interaction between a semi-solid formulation and the skin.