A carrier you cannot see
Nanomedicine is medicine carried by objects too small to see — particles roughly between 10 and 200 nanometres across. A nanometre is a millionth of a millimetre, so even a 100 nm nanoparticle is about a thousand times smaller than a grain of pollen. At this size a carrier behaves less like a tiny pill and more like a large molecule that the body's cells and blood vessels can interact with directly.
Most of these carriers are technically a colloid: solid or liquid droplets dispersed so finely in water that they never settle. That is why much of what you learned about surface forces, zeta potential and surfactants in disperse systems carries straight over — a nanomedicine is a colloidal drug delivery system first, and a clever one second.
Why bother making something so small
A nanocarrier earns its complexity only when it solves a problem a tablet cannot. The recurring reasons are these:
- Dissolve the undissolvable. A poorly soluble drug can be hidden inside the oily or polymeric core of a nanocarrier, so a molecule that would never enter solution on its own can still travel in the blood and raise bioavailability.
- Protect a fragile cargo. Proteins, RNA and other biologics degrade fast in body fluids. Wrapping them shields them from enzymes until they reach the cell.
- Change where the drug goes. Because their size and surface can be tuned, nanocarriers favour some tissues over others — the basis of drug targeting and the EPR effect explored later in this track.
The vocabulary you will keep meeting
Three numbers describe almost any nanomedicine. Particle size (and how tightly it is distributed) governs where it can go. Surface charge, measured as zeta potential, governs whether it stays apart or clumps and how cells greet it. And drug loading with encapsulation efficiency tells you how much medicine is actually inside versus wasted. Keep these three in mind and every carrier in this track becomes easier to read.