Introduction
Nanotechnology uses structures of roughly 1 to 100 nm, the size range of proteins and viruses. In medicine, its best-known use is nanocarriers, which take a drug where it is needed and protect healthy tissue.
Characteristics of nanomaterials
- Large surface area for their volume: this makes them reactive and able to carry a lot of drug.
- New physical properties: at this scale, optical, magnetic and electrical properties can differ from those of the bulk material.
- Small size: they can pass through some biological barriers and enter cells.
- Adjustable surface: molecules can be attached to change how the particle behaves in the body.
Targeting
- Passive targeting: tumor blood vessels are leaky and drainage is poor, so nanoparticles collect there. This is the enhanced permeability and retention effect.
- Active targeting: ligands such as antibodies or folate are attached to the carrier, so it binds to receptors on the target cells.
Controlled release
A carrier should hold its drug during transport and release it at the target. Release can be triggered by:
- Lower pH in tumors or inside endosomes
- Enzymes found at the target
- Outside signals, such as heat, light or a magnetic field