The enhanced surface permeability and retention effect of topically administrated nanoparticles.

Topical administration provides direct way for nanoparticles (NPs) to reach the tumour surface, inducing a more localised and direct therapeutic effect than what intravenous therapy can do and meanwhile guaranteeing higher biosafety. By leveraging the unique surface structure of tumours, these particles undergo intracavity diffusion and afterwards targeted transport into the tumour tissue, which is termed as the enhanced surface permeability and retention (ESPR) effect. Importantly, the ESPR effect of intracavity nanoparticles via topical administration does not rely on tumour-targeted ligand-receptor interactions. In this review, the current clinical status of topical administration-based therapy is updated, the mechanism of the ESPR effect is elucidated and how to modulate the ESPR effect is summarised.