A novel 3D-printed tool for <i>in vitro</i> cell interaction studies under flow conditions.

Abstract

The interaction of drug formulations with cells is a critical factor in the development of effective therapeutics. Conventional <i>in vitro</i> models, such as static horizontal monolayer cultures, often fail to account for key parameters such as sedimentation, flotation or shear stress, which influence the cellular dose and interaction dynamics. In this study, the FlowCube, an <i>in vitro</i> platform designed to simulate dynamic flow conditions was used to investigate the impact of motion and cell layer orientation on the cell interaction of various particle formulations. Polymeric nanoparticles, microparticles, and buoyant microcapsules were prepared and characterized for size, stability, and sedimentation behaviour. Cell binding of these particles, along with a dissolved lectin ligand as a model soluble substance, was evaluated using the FlowCube and compared with horizontal multiwell plate experiments. Microparticles exhibited significantly lower cell association with vertically oriented cell layers in the FlowCube than with horizontal monolayers, indicating sedimentation-driven accumulation under static conditions. In contrast, buoyant microcapsules showed enhanced cell interaction in the FlowCube, highlighting the role of density-dependent particle dynamics. Cell association of the soluble ligand and the nanoparticle formulation were rather affected by the induced shear stress. These findings demonstrate the critical role of sedimentation, flotation, and shear stress in drug formulation-cell interactions and highlight the need to incorporate controlled motion and consider cell layer orientation for more reliable, physiologically relevant outcomes. The FlowCube is a versatile and valuable addition to conventional <i>in vitro</i> models with the potential to improve the accuracy, reproducibility, and translational relevance of <i>in vitro</i> drug formulation studies.