Abstract

Rapid Manufacturing of mRNA Lipid Nanoparticles in a 3D Printed Microfluidic Device

Noah Malmstadt, Professor of Chemical Engineering and Materials Science, University of Southern California

Lipid nanoparticles (LNPs) have proven to be effective delivery vehicles for mRNA payloads, with LNP-based vaccines proving highly effective in combating the SARS-CoV-2 virus. Beyond mRNA vaccines, LNPs have broad applications in oligonucleotide delivery for a host of applications. LNPs are assembled on the basis of ionic interactions between polyanionic oligonucleotides and cationic lipids; control over the total lipid composition of the particle allows for its pharmacological properties to be engineered. Assembly of the oligonucleotide-lipid complex requires rapid mixing on short length- and time-scales. This is typically accomplished in microfluidic channels, often with channel features such as staggered herringbone mixers (SHMs) to facilitate rapid homogenization of the lipid (in ethanol solution) and oligonucleotide (in aqueous solution) streams. We have designed a 3D-printable microfluidic device that improves on the LNP manufacturing state of the art in terms of both particle uniformity and manufacturing throughput. This is facilitated by the unique advantages that 3D printing brings to microfluidic fabrication. For instance, the lipid and RNA streams are brought together at a junction that focuses the lipid stream in two orthogonal planes, centering it in the channel where it is in uniform contact with the RNA stream. The combined streams are then mixed in a SHM that is routed in three dimensions along a zig-zag path, adding chaotic advection mixing beyond that which is achieved by a simple linear SHM.

Using a lipid composition and mRNA sequence that matches the make-up of the Moderna SARS-CoV-2 vaccine, we were able to produce highly uniform LNPs that matched the size and nanostructure of the particles present in the commercial vaccine. The encapsulation efficiency of RNA in our device, which can exceed 90% with the proper flow rate tuning, is greater than that of currently available commercial LNP manufacturing devices.