Finding the Needle in the Haystack: High-Resolution Techniques for Characterization of Mixed Protein Particles Containing Shed Silicone Rubber Particles Generated During Pumping

During the manufacturing process of biopharmaceuticals, peristaltic pumps are employed at different stages for transferring and dosing of the final product. Commonly used silicone tubings are known for particle shedding from the inner tubing surface due to friction in the pump head. These nanometer sized silicone rubber particles could interfere with proteins. Until now, only mixed protein particles containing micrometer-sized contaminations such as silicone oil have been characterized, detected, and quantified. To overcome the detection limits in particle sizes of contaminants, this study aimed for the definite identification of protein particles containing nanometer sized silicone particles in qualitative and quantitative manner. The mixed particles consisted of silicone rubber particles either coated with a protein monolayer or embedded into protein aggregates. Confocal Raman microscopy allows label free chemical identification of components and 3D particle imaging. Labeling the tubing enables high-resolution imaging via confocal laser scanning microscopy and counting of mixed particles via Imaging Flow Cytometry. Overall, these methods allow the detection and identification of particles of unknown origin and composition and could be a forensic tool for solving problems with contaminations during processing of biopharmaceuticals.