How a drug is smuggled past the blood–brain barrier
The brain refuses almost every drug molecule, and it is right to. One slider follows the trick the labs are trying instead: wrap the molecule in a bubble the wall already knows how to carry.
Stage The barrier
- 0
- 1
- 2
- 3
- 4
Tap a part of the diagram to open that stage.
What is actually being bought
The barrier does not sort by usefulness, it sorts by identity. Exosome delivery neither breaks the wall nor opens a hole in it — it hands the wall something the wall already has a routine for and lets the routine do the carrying. The whole gain is the difference between a molecule that bounces and one that gets a ride.
What's inside
- 1 A wall made of sealed joints — The barrier is not a defect. Anything that gets in easily can also poison you easily.
- 2 The drug is wrapped in a vesicle cells already use — The wrapper is not a delivery box. It is an identity the wall already accepts.
- 3 Peptides say where the bubble should stop — Targeting adds no force. It adds the chance of being picked up at the right wall.
- 4 The wall picks the vesicle up and carries it across — Plenty of vesicles that get in are digested on the way. Escaping that compartment is still the hard part.
- 5 The cargo is let go where it was aimed — This is a mechanism in trials, not a medicine on a shelf: yield, dosing and safety are all still open questions.
Explorable Explanations
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- Proving a secret without revealing it One slider walks through the stages, the other adds rounds. Watch certainty climb to almost total while the secret stays a secret.
- Getting lithium out of brine: ponds versus direct extraction Move the slider through five stages and compare two ways of taking the same metal out of the same salt water.
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- How search over your documents works Move the sliders and watch a search pipeline decide what the model is allowed to see — and what happens when it is fed the wrong passage.
- Retries and slow responses The network drops in the middle of an operation. Press the button twice and see what ends up in the database — with an idempotency key and without one.
- How a language model writes The weights are frozen and nothing is remembered. Pull the sliders and watch the model pick the next piece of text, over and over.
- How a language model learns Pull one slider and watch a pile of random numbers turn into a prediction over a thousand training steps.
- Where electricity comes from Pull one slider and follow the energy from a river all the way to a pump that lifts water back up.