Better storage buffers could pave way for safer mRNA therapies

Researchers at The University of Texas at Austin have teamed up with pharmaceutical leader Eli Lilly and Company to uncover new information about mRNA lipid nanoparticles (LNPs), the technology behind COVID-19 vaccines and other important treatments, and how to make it more effective.

The joint study, which also includes researchers from Boston University, focuses on how mRNA-LNP therapeutics are stored and distributed across the globe, often frozen, and how those conditions affect how well these particles work by the time they get to the patient. Choosing the right “storage buffers” can directly shape the nanoparticle’s internal structure, which governs how efficiently the mRNA is delivered into cells and turned into protein. This critical step ultimately determines the treatment’s effectiveness, whether it’s for a vaccine or a gene-editing therapy.

“Our study shows that something as simple as the storage solution can make a huge difference in how well mRNA medicines work,” said Alex Marras, an assistant professor in the Cockrell School of Engineering’s Walker Department of Mechanical Engineering and one of the lead researchers of the research published in ACS Nano. “By understanding how the buffer molecules influence particle nanostructure and their interactions with cellular compartments, we can help make these therapies more stable and effective, even after they’ve been frozen and shipped around the world.”

Tiny mRNA carriers called lipid nanoparticles deliver genetic instructions into cells, prompting them to make proteins that treat or prevent disease. This system, the researchers say, is the gold standard for delivering therapeutic RNA, but it still faces challenges.

The buffer solution is used to keep these nanoparticles stable during freezing and shipping, but this has proven to be a major challenge as these nanoparticle vehicles can be sensitive to changes in properties like size, uniformity, or how well they encapsulate their therapeutic mRNA cargo.

The research team investigated how different storage buffers-specifically Tris, histidine, and citrate-affect the internal structure, stability, and delivery efficiency of mRNA-LNPs. Their experiments revealed that the type and concentration of buffer not only influence how well the nanoparticles survive freezing and thawing, but also the structural changes the particles undergo during delivery, which control how effectively they deliver mRNA into cells.

Citrate buffer helped the nanoparticles deliver mRNA more efficiently when stored in the refrigerator, but could not protect them during freezing. The Tris buffer improved potency after freezing and thawing, preserving stability, the desired internal structure, and delivery of mRNA.

“These lipid nanoparticles protect mRNA and help deliver it into cells, but the nanoparticles themselves are also sensitive to their storage environment,” said Meysam Mohammadi-Zerankeshi, a Ph.D. student in Marras’ lab who was the first author on the new paper. “if they become unstable during freezing and thawing, they can aggregate or lose their cargo, reducing delivery efficiency, then the treatments don’t work.”

Marras’ collaborations with Lilly, which date back several years in collaboration with UT Austin Chemical Engineering Professor Keith Johnston and include other projects focused on antibodies and siRNA, gave the researchers access to additional tools and pharmaceutically relevant samples. These opportunities allowed them to do more than they could in the academic setting, primarily in scaling up nanoparticle synthesis and testing them across four human cell lines. 

Adding the mechanistic understanding of RNA-lipid interactions in LNPs through academic collaboration enables Lilly to better design therapeutics. By optimizing storage buffers, manufacturers can produce more robust mRNA vaccines and treatments, ensuring patients receive the full benefit of these medicines. Even the best mRNA vaccines, like the COVID vaccine, have a lot of room for improvement. Roughly 5-10% of mRNA is properly delivered to the target. Any improvement on that could reduce side effects of these therapies.

One way to overcome inefficient delivery is simply to give more material, but higher doses can also increase side effects. That’s part of why you might feel rough for a day or two after an RNA vaccine. If we can make these nanoparticles more efficient, we may be able to achieve the same therapeutic effect with a lower dose, potentially reducing those side effects and making these treatments easier on patients.”

Alex Marras, Assistant Professor, Cockrell School of Engineering, University of Texas at Austin