Replacing the emulsion for bake-on siliconization of containers - comparison of emulsion stability and container performance in the context of protein formulations.

Pre-filled syringes have simplified parenteral administration of protein drugs. To ensure an easy and consistent movement of the plunger, the inner glass container surface is typically siliconized. For bake-on siliconization emulsions are sprayed on and heat treated. Due to the European Union regulation REACh (Regulation concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals) the use of certain emulsion components, partially constituting the gold standard Liveo™ 365 35% Dimethicone NF Emulsion (Liveo™ 365), becomes restricted and Liveo™ 366 35% Dimethicone NF Emulsion (Liveo™ 366) has been introduced as an alternative. This change may affect the handling properties as well as the silicone layer formed. The purpose of these studies was to identify any differences that may influence the stability and safety of the final drug/device combination product to enable the use of the new emulsion. We compared silicone emulsions Liveo™ 365 and Liveo™ 366 and dilutions focusing on I) their general physical stability, II) the thermal degradation process of the emulsions and their components, and III) the resulting silicone layer concerning chemistry, morphology, and functionality. The results were linked to the assessment of the final product regarding particle formation and long-term stability. A comparison of the emulsions Liveo™ 365 and Liveo™ 366 for bake-on siliconization is presented to support the transition of the latter as it becomes mandatory with REACh. Our studies show that the two emulsions do not significantly differ with respect to handling and stability, the resultant silicone layer characteristics as well as its functionality. We conclude that the transition to the new emulsion will not significantly impact the final product or the layer performance upon storage and with respect to particle formation.