Initially, this professor at Stanford, California, was just looking to be able to observe the evolution of certain molecules on the surface of cancer cells.
Today, thanks to her discoveries, at least two companies - including one she co-founded - are developing innovative cancer treatments.
But the multitude of applications allowed by his invention is impressive: delivering a remedy in an ultra-precise way, identifying drug targets in the body, visualizing certain bacteria...
"The majority of them, I would never have imagined them in 1997", during her very first project, she told AFP.
But it is the magnitude of this discovery, called bioorthogonal chemistry, that the Nobel Prize committee hailed on Wednesday by making her the eighth woman crowned with the chemistry prize, at only 55 years old.
Her passion for organic chemistry came to her during a course at Harvard, when she began studying medicine.
The material has the reputation of being difficult, even impenetrable.
But thanks to an "extraordinary teacher" whom she says without hesitation that he "changed (s) his life", she "falls in love with the subject".
"I said, we forget medicine, I will be a chemist", says the one whose sister is a professor of applied mathematics, and the father a retired physics professor.
Arriving at UC Berkeley at the end of her studies, she wants to take a closer look at glycans: carbohydrates located on the surface of cells, which "change structurally" when they become cancerous.
But at the time, "there was no way to visualize these carbohydrates", for example under a microscope, explains Carolyn Bertozzi.
His idea: to use two chemical substances that go together perfectly, like legos.
The first lego is introduced into the cell via a sugar.
Once metabolized, this lego is placed at the end of the glycan, on the surface of the cell.
Then the second lego is injected into the body, being equipped with a fluorescent molecule.
The two legos fit together, and voila: the famous carbohydrates can be seen under a microscope.
This technique is inspired by "click chemistry" developed separately by the Dane Morten Meldal and the American Barry Sharpless - also awarded the Nobel on Wednesday.
But then they use copper, which is toxic to the body.
Carolyn Bertozzi's achievement is to have made this reaction possible in the human body, without copper.
Another feat: these legos do not fit together with any of the "millions of other very similar toys" present in the body, explains the researcher with pedagogy.
This is why she baptizes this chemistry "bioorthogonal", which means: which does not interact with the living.
Perfecting the technique took him 10 years.
"Cycle of Science"
Thanks to this breakthrough, Carolyn Bertozzi can now better understand the process at work when cancer develops.
"These carbohydrates on the surface of the cancer cell are able to hide the diseased cell from the eyes of the immune system, to make it invisible. So your body can't fight it, because it can't see it," she explains. .
This observation is at the origin of the development of a drug currently in the first phase of clinical trials, and acting "like a mower", she says very seriously.
The first lego attaches to the cancer cell, and the second, which clips onto it, is equipped with an enzyme that "mows carbohydrates as if they were grass", she says in a smile.
Another company is looking to use the technique to better target the administration of the treatment.
A first lego is injected into the tumor, then a second, which carries the drug, attaches itself to it and then releases a large dose, right in the right place.
This should allow the doctor to "treat the tumor without exposing the whole body to a toxic product", welcomed Carolyn Bertozzi during a press conference.
Clinical trials are also underway.
What does the future hold for these finds?
“I hope for an impact on human health,” she replies.
"But those who will decide this more than me are my students," says the one who has seen 250 pass - all of whom hastened to fill her mailbox with congratulatory messages on Wednesday.
"That's the cycle of science. To be guided, then to guide afterwards", she underlines.
And "guiding students gives you the opportunity to amplify the impact of your scientific discoveries."
© 2022 AFP