(115d) Pickering foam Formulation By Wet Nano-Milling

Pickering foams or emulsions are very interesting formulations because they are stabilized by solid particles instead of surfactants. We observed during formulation of a nano suspension of a hydrophobic API by wet ball milling spontaneous undesirable formation of a viscous foam, which was stabilized by solid nanoparticles dispersed in water. We have prepared a Pickering foam by the milling of a hydrophobic API suspension in a flow-through ball mill Netsch LabStar by zirconium dioxide balls as the milling media. We have characterized the particle size distribution (PSD) of the API particles in the foam by static light scattering and Scanning Electron Microscopy (SEM). We have studied the 3D structure of the foam and calculated its porosity using micro CT and confocal optical microscopy. A Pickering foam produced by the ball nano-milling process is stabilized by the solid particles of the hydrophobic API. The foam formation time is dependent on the initial surfactant concentrations used in the milling process. Mechanical properties such as viscosity are dependent on the milling time and increase because of increasing number of stabilizing particles and their surface area. Solid nanoparticles can be used as emulsifiers for the stabilisation of the Pickering foams or emulsions, which have advantages compared to surfactant stabilized formulations. Sometimes the formation of a Pickering foam can be a spontaneous and unwanted phenomenon, which causes a change of mechanical properties of the material and makes the technological process more challenging. To avoid undesired complications of the technological process, it is important to know what causes the changes and to know how to avoid them. This was achieved by studying the undesirable Pickering foam produced by the formulation of a nanosuspension. The foam creation is significantly dependent on the surfactant concentration relative to the specific surface area of the hydrophobic API.

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