Contact Angle Measurement on Glass Surfaces of Injection Solution Containers Application of force tensiometry as a tool for contact angle measurement on strongly curved hydrophobic glass surfaces of pharmaceutical packaging containers

Dynamic contact angle measurement was performed on primary packaging containers made from non-treated glass and with silicone surface coating. The goal of this study was to quantify the hydrophobicity of glass surfaces. As a measure of the interaction, the contact angle of the glass surface with a liquid was measured by force tensiometry (wetted length method). This method can measure the contact angle of liquids on a curved surface. The reference measurement was the contact angle of water for injection (WFI) on non-treated and impregnated glass surfaces, then the contact angles between three aqueous protein product solutions and non-treated and impregnated glass cartridges were measured by the same procedure. The contact angle of water and the protein solutions with the non-treated glass cartridges was found to be 0 degrees, which is an expected value for a clean glass surface. The advancing contact angle of WFI as well as the investigated protein solutions with the siliconized glass surfaces was found to be 60-95 degrees. The non-treated cartridges were coated with polydimethylsiloxane and siliconized by a burning-in process. The advancing contact angles measured on siliconized glass surfaces were higher than those measured on non-treated glass surfaces, i.e., on siliconized glass surfaces poor wetting was observed for water and all three aqueous protein solutions. The siliconized glass surfaces are more hydrophobic than non-treated glass. The results show that the applied force tensiometry method is capable of detecting differences in wetting behaviour on strongly curved glass surfaces.