Lesson Plan

The Blood Foam

1940 to 1944, Boston, Pearl Harbor, North Africa, Normandy • McGill click-clotting (Jiang et al, Nature, 29 April 2026): bio-orthogonal crosslinking of red blood cells gels in 5 seconds, 13× tougher and 4× more adhesive than a native clot. • May 5, 2026

Before using this lesson plan: Read the full story or listen to the 6-minute narration (works as a bell-ringer).

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Lesson Plan: The Blood Foam

Subject area

STEM: chemistry, physiology, surgery, history of medicine, materials science.

Recommended audience

High-school biology and chemistry (Years 11-13 / Grades 10-12)

First-year undergraduate physiology, biochemistry, or biomedical engineering

General STEM enrichment for ages 14+

Lesson length

60-75 minutes (one period plus optional follow-up).

Learning objectives

By the end of the lesson, students will be able to:

Describe what blood plasma is and explain why fractionating it into separate proteins was a useful wartime project.

Outline the Cohn process and identify the role of cold ethanol in selective protein precipitation.

Explain how albumin treats burn shock physiologically.

Describe how fibrin foam works as a haemostatic agent and why it was particularly useful in neurosurgery.

Place the McGill 2026 click-clotting result in the long history of haemostasis from cautery to cyanoacrylate.

Compare the engineered blood clot's mechanical properties to a native clot and explain what bio-orthogonal chemistry means in this context.

Key terms

Plasma, serum, fibrin, fibrinogen, thrombin, albumin, gamma globulin

Plasma fractionation, ethanol precipitation, lyophilisation

Burn shock, capillary leak, oncotic pressure

Haemostasis, cautery, ligature, antisepsis

Click chemistry, bio-orthogonal reactions

Crosslinking, fracture toughness, adhesion energy

Autologous, allogeneic

Pre-class preparation

Have a periodic table on the wall.

Bring a small clear bottle (suggesting a 250 ml plasma unit) for visual reference.

A printed image of a 1944 fibrin foam sponge and a photograph of the McGill click-clot result, if available, side by side.

Lesson outline

1. Hook (5 min): "every bottle in Boston"

Describe the cold open. On 8 December 1941, the day after Pearl Harbor, every bottle of human albumin solution in Boston was put on a military aircraft and flown to Hawaii. Lieutenant Colonel Isidor Ravdin treated seven critically burned sailors at Pearl Harbor with the albumin and all seven survived. Pose the central question: where did the albumin come from, and why was it the right substance to give to a burned sailor?

2. What is blood plasma? (10 min)

Blood is a tissue. Roughly 55% plasma (a clear pale-yellow liquid), 45% cellular (red cells, white cells, platelets).

Plasma is mostly water (~92%) with a complex mix of proteins, electrolytes, hormones, glucose, and waste products.

Proteins of interest in this story: albumin (the most abundant, ~50% of plasma protein), gamma globulins (antibodies), fibrinogen and thrombin (the clotting cascade), and many smaller players.

Discuss why whole blood is fragile: it has a short shelf life, must be ABO-matched, requires refrigeration, cannot be carried in a haversack.

Discuss why plasma alone was already in use as a partial substitute, and why fractionating plasma into individual proteins would let medics carry the right protein for the right wound.

3. The Cohn process (15 min)

Edwin Cohn was a physical chemist at Harvard Medical School. The National Research Council approached him in 1940 with $6,500 and a question: can plasma be split into useable parts at industrial scale?

His answer: yes, with cold ethanol added in stages, at carefully controlled pH and ionic strength.

Walk through the chemistry. Different proteins have different solubility profiles. Each protein precipitates at a different combination of:

The fractions in order: albumin first, then gamma globulins, then fibrinogen, then thrombin, then smaller proteins.

Each fraction can be lyophilised (freeze-dried) into a stable white powder, packed in a cardboard box, and shipped anywhere.

Note: the Cohn process is in essence still how plasma fractionation is done in 2026, eighty-five years later. Look up "Cohn fraction V" online.

4. Why albumin saves a burn victim (10 min)

Set the physiology. A serious burn destroys skin. The capillaries underneath leak fluid into the soft tissues. The patient becomes "third-spaced": the water that should be inside the blood vessels is now in the swelling.

The blood pressure falls. The veins flatten. The heart cannot fill. Without intervention the patient dies of shock within hours.

Albumin holds water in the bloodstream by oncotic pressure. Run human albumin into a deep vein and the water comes back out of the swelling, the blood pressure climbs, the heart fills, the patient wakes up.

Discussion question: why didn't earlier physicians just give salt water? Answer: salt water has no oncotic pressure; it leaks straight back out into the same swelling. You need a large molecule that the capillary wall cannot pass.

Discuss the Pearl Harbor case again with this physiology in mind.

5. Fibrin foam: a sponge that becomes a clot (10 min)

Two of Cohn's collaborators: Franc Ingraham (neurosurgeon at Children's Hospital Boston) and Orville Bailey (pathologist at Peter Bent Brigham), reported in the very first issue of the Journal of Neurosurgery in July 1944.

The product: a small dehydrated open-pore sponge of fibrin, prepared from the fibrinogen fraction of Cohn's plant.

The procedure: surgeon cuts a small piece of foam, dips it in thrombin solution, presses it onto bleeding tissue. The thrombin converts the fibrinogen in the sponge to fibrin in seconds. The clot forms inside the sponge. Bleeding stops in about twenty seconds. The sponge, being itself fibrin, is reabsorbed by the body. Nothing has to be removed.

Why neurosurgery in particular? Brain tissue cannot be clamped or sutured the way an artery in a leg can be clamped. Electrocautery risks burning the very tissue you are trying to preserve. The surgeon may have only seconds before the patient is brain-dead.

Pre-1944, bleeding from inside the skull was, for most of the four millennia of recorded surgery, a death sentence. After 1944 it was a problem with a tool.

6. The long history of haemostasis (10 min)

Egyptian physicians cauterised wounds with red-hot iron (Edwin Smith Papyrus, c. 1600 BC).

Galen (c. 175 AD): vinegar and pressure.

Ambroise Paré (1536): silk ligatures around bleeding arteries instead of cautery, after observing that wounds dressed with egg yolk and turpentine healed better than wounds cauterised with boiling oil.

Joseph Lister (1867): antisepsis, carbolic acid spray. Bleeding wounds no longer reliably became septic.

Twentieth century: the haemostatic clamp, the electrocautery, the gelatin sponge.

Each generation believed it had finished the war on bleeding. Each was overtaken by the next.

7. The 2026 click-clot (10 min)

29 April 2026, Nature, Bakewell? No: Jiang et al, with senior author Jianyu Li, McGill University Department of Mechanical Engineering. Title: "Engineering tough blood clots for rapid haemostasis and enhanced regeneration."

The technique. A solution of red blood cells (donor or autologous) is mixed with a small molecule that places matched chemical handles on the surface proteins of each cell. A second molecule, added with a syringe, locks the handles together in a fast bio-orthogonal reaction. The cells crosslink into a solid gel in five seconds.

"Bio-orthogonal" means the reaction does not interfere with normal biology: it ignores all the proteins, sugars, lipids and nucleic acids in the body and only reacts with the artificial handles you have placed. Click chemistry was awarded the Nobel Prize for chemistry in 2022 to Bertozzi, Sharpless, and Meldal for exactly this reason.

Performance:

Discussion: why does fracture toughness matter in a clot? A clot that snaps under load is a clot that lets the wound rebleed when the patient moves. A clot that stretches and holds keeps the seal.

8. Wrap and assignment (5 min)

Pose: "Each generation thinks it has finished the war on bleeding. What might the 2050 answer look like?"

Optional homework: write a 500-word account of what happened to one specific bottle of Cohn albumin from a Boston pilot plant in 1942 to a wounded soldier on a Pacific reef in 1943. Include the chemistry of how it was prepared, how it was packaged, how it was administered, and why it saved the soldier's life.

Discussion questions

Plasma is mostly water and a complex mix of proteins. Why was it useful to separate the proteins instead of using whole plasma?

How does cold ethanol selectively precipitate proteins? Use the concepts of dielectric constant, charge, and hydration shell in your answer.

Why does albumin reverse burn shock and salt water does not?

Why was fibrin foam particularly useful in brain surgery? Name two physical features of brain tissue that make conventional haemostatic techniques inappropriate.

The McGill click-clot uses bio-orthogonal chemistry. What does "bio-orthogonal" mean, and why is that property essential for any chemistry that takes place inside a living organism?

The McGill clot is 13 times more fracture-resistant than a natural clot. Why might a 4-fold increase in adhesion energy matter just as much as a 13-fold increase in toughness for a clinical wound dressing?

Edwin Cohn's process for plasma fractionation, conceived in 1940, is in essence still in use in 2026. Why have so few innovations replaced it? Compare with the rapid replacement cycle of haemostatic agents.

Extension activities

Lab demonstration (where facilities allow): demonstrate the precipitation of egg-white albumin with progressive amounts of cold ethanol. Use a turbidity measurement (a simple absorbance reading) at each ethanol concentration to plot a precipitation curve.

Calculation: the McGill paper reports a 13-fold increase in fracture toughness. If a normal clot has a fracture toughness of approximately 1 J/m², estimate the toughness of the engineered clot. Compare to the toughness of cartilage (~1000 J/m²) and rubber (~5000 J/m²).

Research project: read the original 1944 Ingraham and Bailey paper (J Neurosurg 1: 23-39) and write a 1000-word paper comparing it with the 2026 Jiang et al paper in Nature. What changed? What stayed the same?

Writing assignment: write a 500-word newspaper-style article reporting the McGill cyto-gel result to a non-scientific audience. Include one quote from Dr Li, one from a sceptical surgeon, and one from a haemophiliac patient who might one day benefit.

Time Rhymes