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A few years ago, Limoges university[br]hospital practitioners

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and Faculty of Medicine researchers

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were in discussion.

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And they wanted to know[br]if there was something

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that might aid them[br]during cancer surgeries.

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What they found[br]did not really satisfy them.

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So, they straightway[br]launched a research program.

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This research involved medics,

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researchers in biology,[br]in chemistry, physicists,

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from various institutes,[br]and from various organizations.

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The first time I heard[br]of this research program and its work,

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I was right away attracted by the elegance[br]of the solution it proposed.

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And then I saw very quickly

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the incredible impact[br]this technology could have for patients.

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So I decided to quit my job to dedicate[br]all of my time to this project,

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and I was joined by two friends,[br]Alexis and Virgile.

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Today, we are trying to transform

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this beautiful technology[br]into a real tool.

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So, how can we see what is not visible?

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Most of what surrounds us[br]that we call invisible

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is just too small for us to perceive.

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It's the case, for example, in diseases[br]that we cannot see directly.

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What we can see are the symptoms[br]that inform us that something is wrong.

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Certain diseases come[br]from external factors

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like viruses or, say, bacteria.

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Other illnesses come from our own body.

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That's the case for cancer.

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Throughout our life,[br]right now as I am talking to you,

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all of us, we all have cells[br]that regenerate and renew themselves

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in a cycle that we might consider[br]to be birth, life, and death.

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All this at the cellular level.

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For example, the liver renews[br]all of its cells in 400 days.

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This is not an excuse[br]for your next night out -

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you will agree.

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And some other cells[br]are renewed even faster.

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That's the case for the intestine.

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The intestine renews its cells[br]entirely every five days.

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And during our entire life,[br]we are all going to lose

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about the equivalent[br]of 20 kg of dead skin.

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Think about that[br]when you see dust at home.

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Unfortunately, in this process,[br]some cells may degenerate.

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This can have several causes:

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our lifestyle, inherited factors,[br]or our environment.

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And these cells will start to degenerate.

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For example, some of them[br]will become immortal.

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When I first heard[br]some cells become immortal,

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I thought we were all going to live long.

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In fact, no, it just brings[br]processes to a complete end,

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with the consequence[br]that the organ becomes non-functional.

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So, at the root of a disease as serious,[br]as terrible, as cancer,

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there are just tiny cells.

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And a cell measures about 10 micrometres,

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which is nearly 10 times smaller[br]than the diameter of a hair.

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It is really small.

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(Applause)

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They are tiny, and cannot be seen[br]with the naked eye.

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They also have an incredible quality[br]that is really vicious,

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which is that they make themselves[br]invisible to our immune system,

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and so our body cannot[br]defend itself against them.

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There are different methods[br]to discover cancerous lesions.

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For example, tumour marking:

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We take a sample, we mark it,

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and we get to detecting lesions

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of several tens of thousands[br]of cancerous cells.

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There's also imaging.

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We inject a tracer into the patient,

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use a device like[br]a PET scanner or a scintigraph,

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and we can see lesions[br]of a few millimetres in size.

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But already, the cancer[br]consists of tens of millions,

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even hundreds of millions, of cells.

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For a tumour to be[br]visible to the naked eye,

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when it's nearly a centimetre across,

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we're into hundreds of millions of cells,

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even billions.

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During the life of the patient,

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most of these cancers are going[br]to be treated by surgical means.

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That is, a man or a woman[br]will go to this organ,

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which she or he knows is sick,[br]and will remove the tumour cells.

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But at some point, despite[br]all their expertise and experience,

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they'll need to ask themselves:

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Should I continue[br]to scrape away at this organ?

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Should I continue to remove[br]a small part of this organ?

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If I continue, I may remove[br]some healthy, functional tissue,

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and I may thus compromise[br]my patient's quality of life.

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That's very clear when it's about[br]lesions in the brain, for example.

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On the other hand, if I stop,[br]if I leave it as it is,

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I take the risk of there[br]remaining cancer cells,

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and then the cancer[br]may come back and re-advance.

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It is precisely to see[br]the invisible boundary

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between healthy cells[br]and those that are cancerous

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that this project was started.

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Imagine a cell.

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So here, clearly, I shrank.

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On this cell, there are[br]lots of tiny molecules.

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These small molecules, all different,

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can tell us about the internal functioning[br]and mechanism of the cell.

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So, all we have to do is find the molecule[br]that tells us the cell is cancerous,

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and we're there.

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In biology, there are antibodies -[br]you've already heard about them -

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and antibodies know how to do many things,

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in particular, to recognize[br]and hook onto these molecules.

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And onto our antibody,[br]we can hook a fluorophore,

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a type of biological lantern

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that re-emits light[br]when light is shone on it.

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So, we attach this fluorophore[br]to our antibody,

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and the moment our antibody[br]hooks onto the molecule,

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it will signal to us[br]that that one is cancerous.

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This is already a very big step.

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But they went even further[br]in their research.

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It so happens that when the antibody[br]hooks its molecule, it changes shape,

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it's as if it folds its arms.

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And this is great because there is[br]another physical effect called FRET -

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Förster Resonance Energy Transfer.

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I feel like I've lost you all.

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This superb effect - it's quite easy[br]to understand, but it's incredible.

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You have two fluorophores,[br]of different colours, one red, one green.

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Each shines in its place,

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but at a given moment,[br]at a really precise distance,

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they will exchange their energy,[br]one will transfer its energy to the other.

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And so our green fluorophore[br]begins to become dimmer,

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while the red fluorophore[br]begins to become much more intense.

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The idea behind it was[br]to take these two fluorophores,

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hook them to very specific[br]places on our antibody,

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so that when it recognizes[br]a cancerous cell,

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by hooking onto it, it will change colour.

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So, instead of seeing light[br]slightly green and red,

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the surgeon will only see red light,

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telling her or him that she or he[br]should continue to perform their surgery.

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But to go even further,[br]we took these small antibodies

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and put them at the end of a small[br]optical fibre about 2 mm in diameter,

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to come directly into contact[br]with the patient's tissue.

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By injecting a light beam,

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we are able to tell whether or not[br]the tissues are cancerous,

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whether or not to continue[br]to perform the surgery

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to give the patient the best chance.

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It's thanks to this project

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that we can improve[br]the patient's quality of life

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by making detectable what was invisible.

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Thank you.

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(Applause)