Modelling Oxygen Transport, Microcarrier Aggregation, and Hydrodynamic Constraints in Stirred Bioreactors for Scalable Developmental Engineering

Developmental engineering (DE) is a bottom-up strategy for generating functional tissues from modular tissues (MTs), overcoming limitations of conventional top-down approach. This study integrates theoretical simulations with empirical correlations to analyse microcarrier aggregation, oxygen transport, suspension conditions, and cell damage in stirred bioreactors, providing guidance for scalable MT production in DE. Microcarrier aggregates were modelled to evaluate minimum oxygen concentration (Cmin). Results show that larger microcarrier diameters (dmc) increase Cmin because of longer diffusion distances. Aggregate geometry and packing configuration, including hexagonal close packing and the “kissing number,” influence oxygen limitation and explain observed Cmin plateaus. Hydrodynamic behaviour was assessed using Zwietering correlation and Kolmogorov turbulence scaling. Denser microcarrier aggregates require higher minimum stirring speeds (Nmin), while larger dmc increases susceptibility to shear. Aggressive impeller designs and higher revolutions per minute reduce Nmin but increase collision-induced cell damage. In contrast, higher medium density (e.g., 20% FBS) reduces shear stress and energy dissipation. A unified framework is proposed that integrates oxygen diffusion, aggregate geometry, microcarrier properties, and hydrodynamics to predict worst-case oxygen limitation and cell damage. The results clarify trade-offs between impeller design, agitation intensity, and aggregation, supporting scalable MT production using individual or aggregated modular scaffolds for DE-based tissue assembly.