Understanding the Compatibility of Fluoride-Based Radiopharmaceutical Reaction Solutions and PDMS

Microfluidic devices offer unique and exciting benefits when applied to radiopharmaceutical manufacturing, and these platforms are now starting to be integrated into commercial products. The field has strayed away from the use of polydimethylsiloxane (PDMS), the most common microfluidic device material, due to its suspected incompatibility with ¹⁸F, the most commonly used radionuclide. However, existing literature provides conflicting conclusions as to the existence and extent of this incompatibility. In this study, we use several analytical instruments to uncover the underlying interaction between fluoride and PDMS. SEM imaging and profilometry confirm the reactive relationship between the two materials and suggest that this interaction only occurs when the reaction solution is fully evaporated and crystallized salts are in contact with PDMS. Furthermore, GC-MS identifies fluoride-containing volatile species that can account for loss of fluoride in previous studies and additionally reveals an incompatibility between PDMS and K₂CO₃ (a commonly used component of radiofluorination reaction solutions). These results confirm the need for microfluidic radiofluorination devices to avoid the use of PDMS in most contexts but may allow for inexpensive design and testing of liquid state operations (such as concentration, purification, and mixing) using the material.