19 Dec CAN SLOSHING IN AUTOINJECTORS BE HARMFUL TO THE DRUG PRODUCT?
Interface motion and hydrodynamic shear of the liquid slosh during the insertion of syringes upon autoinjector (AI) activation may damage the protein drug molecules. We experimentally investigate the interfacial motion and hydrodynamic shear due to the acceleration and deceleration of syringes. No study to date has focused on quantifying the air entrainment and interfacial stress in the AIs experimentally with a non-invasive approach. We explore the role of solution viscosity, air gap size, syringe acceleration, solution-wall contact angle, and surface tension on the interface dynamics caused by syringe acceleration during autoinjector administration.
Interface motion and hydrodynamic shear induced by the liquid sloshing during the needle insertion upon autoinjector actuation were investigated experimentally, generating insights that may help assess the potential impact on therapeutic medicament molecules inside the syringe during autoinjector activation. The air-liquid interface and the air entrainment area were quantified using high-speed shadowgraph visualization. The strain and shear rate experienced by the liquid during the liquid sloshing was also computed from the velocity field obtained from PIV measurements. The interfacial area and the volume of the fluid subject to high strain and shear rates increased with the air gap height and syringe acceleration and decreased with the Fr. The hydrodynamic shear mainly occurred near the syringe wall and entrained bubbles and sharply increased during deceleration, and the maximum strain and shear rates occurred at the end of the deceleration phase. Thus, the initial air gap volume and syringe wall hydrophobicity could be reduced to minimize sloshing effects. Also, the syringe with a smaller diameter would generate less liquid slosh. Future experiments under similar hydrodynamic stresses, shear, and exposure time would help understand whether these conditions can lead to protein aggregation.