Toward accessible mRNA LNP formulation: systematic evaluation of mixing strategies and key parameters

Although mRNA LNPs are a leading delivery platform, achieving reproducible, high-quality formulations across diverse fabrication techniques remains a challenge. This study systematically investigates the impact of microfluidic architectures - staggered herringbone (SS) and serpentine-only (S) channels - alongside T-junction and rapid pipetting methods. We evaluate how critical parameters, including total flow rate (TFR), flow rate ratio (FRR), and lipid-to-mRNA ratio (N/P ratio), govern LNP size, stability, and transfection efficiency. Our findings demonstrate that streamlined S-channel designs and non-microfluidic methods can yield LNPs functionally equivalent in quality and performance to complex staggered herringbone mixers through precise parameter tuning. Furthermore, in vivo assessment confirms the systemic biocompatibility of the optimized formulations, characterized by stable physiological growth, preserved hepatic and renal function, and an absence of adverse histological changes or tissue damage over 8 weeks. By bridging the gap between fluidic process optimization and long-term systemic tolerability, this work provides a foundational framework for the accessible and reproducible production of mRNA LNPs across varying laboratory environments and production scales.