This is a side-on, 2D cross-section of the same two blood vessels as the 3D version. The top lane is a healthy vessel: its endothelial wall (blue) is unbroken, so nanoparticles just flow past. The bottom lane feeds a tumor: irregular angiogenesis leaves gaps in the wall (pink, with visible breaks) and poor lymphatic drainage means anything that gets out struggles to leave again — the Enhanced Permeability and Retention (EPR) effect.
In Passive only mode, particles that extravasate through a gap random-walk through the tumor interstitium with no discrimination. In Active + passive mode, particles also carry ligands (drawn as a gold ring) that steer them toward the nearest cancer-cell receptor (red dot) once they're in the interstitium — they still need passive EPR leakage to get out of the vessel first.
- Injection rate — nanoparticles entering the bloodstream per second, split evenly between both lanes.
- Vessel permeability — scales how often a particle near a tumor gap actually crosses it per tick (real leaky vasculature varies a lot between tumor types).
- Diffusion strength — scales the Brownian jitter of particles in the bloodstream and interstitium (particle size / temperature analogue).
- EPR accumulation — the fraction of tumor-lane particles that have extravasated so far.
- Targeting efficiency — of extravasated particles, the fraction that went on to bind a receptor (only meaningful in Active + passive mode).