Calculation of injection forces for highly concentrated protein solutions.

Protein solutions often manifest a high viscosity at high solution concentrations, thus impairing injectability. Accordingly, accurate prediction of the injection force based on solution viscosity can greatly support protein formulation and device development. In this study, the shear-dependent viscosity of three concentrated protein solutions is reported, and calculated injection forces obtained by two different mathematical models are compared against measured values. The results show that accurate determination of the needle dimensions and the shear-thinning behavior of the protein solutions is vital for injection force prediction. Additionally, one model delivered more accurate results, particularly for solutions with prominent shear-thinning behavior.