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Funke, Stefanie; Matilainen, Julia; Nalenz, Heiko; Bechtold-Peters, Karoline; Mahler, Hanns-Christian; Vetter, Florian; Müller, Christoph; Bracher, Franz; Friess, Wolfgang (2016): Optimization of the bake-on siliconization of cartridges. Part II: Investigations into burn-in time and temperature. In: European Journal of Pharmaceutics and Biopharmaceutics, Vol. 105: pp. 209-222
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Abstract

Combination products have become popular formats for the delivery of parenteral medications. Bake-on siliconization of glass syringes or cartridges allows good piston break-loose and gliding during injection at low silicone levels. Although widely implemented in industry, still little is known and published on the effect of the bake-on process on the silicone level, layer thickness and chemical composition. In this study, cartridges were bake-on siliconized in a heat-tunnel by varying both temperature from 200 to 350 degrees C for 12 min and time from 5 min to 3 h at 316 degrees C. Furthermore, a heat-oven with air-exchange was established as an experimental model. Heat treatment led to a time- and temperature-dependent decrease in the silicone level and layer thickness. After 1 h at 316 degrees C lubrication was insufficient. The silicone levels substantially decreased between 250 and 316 degrees C after 12 min. After bake-on, the peak molecular weight of the silicone remained unchanged while fractions below 5000 g/mol were removed at 316 and 350 degrees C. Cyclic low molecular weight siloxanes below 500 g/mol were volatilized under all conditions. Despite most of the baked-on silicone was solvent-extractable, contact angle analysis indicated a strong binding of a remaining, thin silicone film to the glass surface. (C) 2016 Elsevier B.V. All rights reserved.