A Microfluidic Dialysis Chip for Continuous Purification of Lipid Nanoparticles

ABSTRACT

Synthesis of lipid nanoparticles (LNPs) for mRNA delivery is now standardized and automated. In contrast, post‐synthesis purification—ethanol removal, clearance of unencapsulated components, and buffer exchange—remains less controlled. Conventional bulk dialysis is time‐consuming, whereas centrifugal ultrafiltration, although rapid, can result in reduced particle recovery and mRNA preservation; both of these laboratory‐scale approaches present limitations for reproducible high‐throughput processing. Here we report a 3D‐printed microfluidic dialysis chip for continuous LNP purification. Mirrored serpentine sample and wash‐buffer channels run counter‐current across a clamped, interchangeable membrane in a three‐layer printed chip. A mass‐transfer model relating ethanol removal to the number of transfer units (NTU) identified channel height as the principal geometric design parameter under the fixed‐flow‐rate conditions tested. At a 100 kDa cut‐off and 25 µL/min, the chip removed >99% ethanol and adjusted pH from 4.0 to 7.4, processing 1 mL in 40 min at steady state. Membrane choice set a trade‐off: Polyethersulfone removed ethanol faster, whereas regenerated cellulose gave the highest particle recovery (83%). Förster resonance energy transfer (FRET) confirmed preserved LNP integrity, and on‐chip purified mRNA‐LNPs matched bulk dialysis in transfection efficiency. Serial or parallel configurations offer a gentle, scalable route to LNP purification.