Enhancing the Injectability of High Concentration Drug Formulations Using Core Annular Flows

Highly concentrated biological drug formulations would offer tremendous benefits to global health, yet they cannot be manually injected using commercial syringes and needles due to their high viscosities. Current approaches to address this problem face several challenges such as crosscontamination, high cost, needle clogging, and protein inactivation. This work reports a simple method to enhance formulation injectability using a core annular flow, where the transport of highly viscous fluids through a needle is enabled by coaxial lubrication by a less viscous fluid. A phase diagram to ensure optimally lubricated flow while minimizing the volume fraction of lubricant injected is established. The technique presented here allows for up to a 7x reduction in injection force for the highest viscosity ratio tested. The role of buoyancy-driven eccentricity in governing nominal pressure reduction is also examined. Finally, the findings are implemented into the development of a double barreled syringe that significantly expands the range of injectable concentrations of several biologic formulations.