Lipid
nanoparticles (LNPs) are gaining recognition as
potentially
effective carriers for delivery of therapeutic agents, including nucleic
acids (DNA and RNA), for the prevention and treatment of various diseases.
Much effort has been devoted to the implementation of microfluidic
techniques for the production of monodisperse and stable LNPs and
the improvement of encapsulation efficiency. Here, we developed three-dimensional
(3D)-printed ring micromixers for the production of size-controllable
and monodispersed LNPs with a high mRNA delivery efficiency. The effects
of flow rate and ring shape asymmetry on the mixing performance were
initially examined. Furthermore, the physicochemical properties (such
as hydrodynamic diameter, polydispersity, and encapsulation efficiency)
of the generated LNPs were quantified as a function of these physical
parameters via biochemical analysis and cryo-electron microscopy imaging.
With a high production rate of 68 mL/min, our 3D-printed ring micromixers
can be used to manufacture LNPs with diameters less than 90 nm, low
polydispersity (<0.2), and high mRNA encapsulation efficiency (>91%).
Despite the simplicity of the ring-shaped mixer structure, we can
produce mRNA-loaded LNPs with exceptional quality and high throughput,
outperforming costly commercial micromixers.