A mRNA encapsulation platform  integrating Fluigent’s FlowEZ

mRNA vaccines, a game-changer in vaccinology

Traditional vaccines are made either of a weakened form of the virus or viral proteins. In contrast, mRNA vaccines only include the instruction needed for the cell to produce a small part of the virus, and thus teach our immune system to recognize it.

Without any risk of gene insertion as injected mRNA are translated into proteins in the cell cytoplasm, these types of vaccines have been proven to be long-lasting and effective with safe immune responses.^1,2

In addition, a key advantage of mRNA vaccines is their simple and rapid manufacturing compared to traditional vaccines, especially since they can be produced in a laboratory without any cell culture requirement.

Figure 1: Mechanism of mRA vaccine in the body after injection.³

How can microfluidics help in developing mRNA vaccines?

Before protecting us from the disease, mRNA should be protected from being destroyed in its free state by chemicals present in our blood and enzymatic degradation during the vaccine injection. To overcome this issue, lipid nanoparticles (LNP) are used as shields through mRNA encapsulation. This approach ensures the circulation of mRNA through the blood toward the targeted cell type. Nonetheless, this process requires homogeneous size and distribution of the lipid nanocarriers, which are key parameters in determining clinical success.

The traditional method, which often consists of slowly injecting the lipid solution into an aqueous phase, lacks control over the encapsulation efficiency and the size of the lipid nanocarriers. In contrast, microfluidics offers the opportunity to master these parameters with high reproducibility, easy automation, and a streamlined process.

In this perspective, Hongjuan Wei et al. developed an automated “on-demand” mRNA preparation platform, which contains a module dedicated to encapsulating mRNA in lipid nanoparticles using a microfluidic approach. This example of a universal platform could be a powerful tool in terms of rapidly generating mRNA treatment to accelerate the progress for the early research and development stage.

The platform included three main components: a polymerase chain reaction (PCR) module to amplify the target DNA templates, a heating–magnet separating–mixing module to provide a mixing platform for in vitro transcription, and the encapsulation module to directly encapsulate mRNA in LNPs. The performance of this platform was evaluated by starting with an enhanced green fluorescent protein (eGFP).

Herein, we will focus on the procedure and results for encapsulating mRNA in lipid nanoparticles through the developed module.

A microfluidic encapsulation module for mRNA LNP

The microfluidic encapsulation technique used in this work is based on a staggered herringbone micromixing chip, Fluigent’s pressure-driven controllers (FlowEZ), and flow sensors (FlowUnit). By pressurizing two separate microfluidic reservoirs that contain the lipid vectors in ethanol and eGFP mRNA in water respectively, the fluids circulate toward the microfluidic chip.

Two FlowUnits (Range L: 0-1000 µL/min) were installed for measuring the flow during the process, and thus regulating the pressure through the FlowEZs. The design of the chip consisted of a Y-junction, that enabled the integration of the two fluids, followed by a serpentine channel where a micromixing occurred and enhanced through the herringbone shapes.

The obtained mRNA-LNP was observed by TEM, analyzed by DLS, and further evaluated by transfection into HEK-293T cells.