Fig. 4

Nanocarriers penetrate from blood circulation (I) into the tumor nucleus (IV) and are responsive to different stimuli. (I − II) Drug delivery systems based on nanocarriers can enhance drug penetration and retention into the tumor tissues via the endothelial gap. Externally stimuli (e.g., heat, light, ultrasound, magnetic fields, etc.) or extracellular stimuli (e.g., acidic TME, thermal radiation, enzymes, etc.) can cause the nanocarriers to release their cargos in the vicinity of the target tissue. (III − IV) Intracellular nanocarriers escape from the endosomes and release their drugs in response to internal stimuli (e.g., pH, reduction, enzyme, etc.) and specifically bind to the target to exert anticancer effects. The figure has been created using Biorender