The particles that the Pfizer and Moderna vaccines rely on are 1/1000th the width of a human hair. They’re called lipid nanoparticles, and they’re revolutionizing medicine as we speak.

The Pfizer and Moderna COVID vaccines work by sending mRNA to your cells. The mRNA tells the cells how to make proteins that block the virus. But you can’t send the mRNA on its own, because it would be repelled and flushed out through the kidneys.

The mRNA needs a wrapper, and that’s where the lipid nanoparticle comes in. The mRNA molecules are negatively charged and so are our cells. These two negatives push each other away. But, the nanoparticle can make it inside the cell.

Once inside the cell, the particle faces another barrier. The cell wraps it in a container called an endosome, because the cell doesn’t want to be contaminated. So, the lipid nanoparticle has to be specially designed to escape that endosomal prison.

Decades of research has gone into these particles, and they can now escape and spread the necessary information into the watery substance inside the cell (called the cytoplasm). Our commitment to funding basic science decades ago is paying off today in ways we could never have anticipated.

I learned a great deal about these incredible particles today at an online seminar hosted by the journal Nature with Kathryn Whitehead of Carnegie Mellon University and Yizhou Dong of Ohio State University. They gave some great perspective on the development of this amazing technology.

One thing Professor Whitehead mentioned was that despite concerns that the mRNA vaccines are too new and unproven to be safe, the lipid nanoparticles they use have existed for decades. In fact, she said she’s had research rejected for publication because these particles are considered too old hat!

I also finally learned why the vaccines have to be stored at such cold temperatures: molecules will start moving around too much once the temperature rises, so the lipid nanoparticles could come apart. Perhaps one reason Moderna’s vaccine doesn’t need quite as cold of storage is that they’ve been researching these particles for much longer than Pfizer/BioNTech, so their particles may be a bit more stable.

Beyond COVID, lipid nanoparticles and the mRNA therapies they’re a part of could be used for other viruses like the flu, Zika and Ebola. They may also be used as cancer immunotherapies. (This echoes what the co-founders of BioNTech said recently.)

These particles seem likely to underlie an entire new generation of medicines. I’ll be keeping a close eye on them, microscopic as they are!

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Photo: “2020_06_020100 – a human cell attacked by Covid-19” by Gwydion M. Williams is licensed under CC BY 2.0

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