Figure 12.

Schematic illustration of a mechanism to enhance the EPR effect and tumor accumulation by ultrafine iron oxide nanoparticles (uIONPs) with bright-to-dark T₁-T₂ MRI contrast switching. uIONPs could extravasate faster and easier from the leaky tumor vessels into a tumor with favorable kinetics and then self-assemble to clusters in the tumor interstitial space with relatively low pH (~6.5), thus restricting clustered uIONPs intravasation back into blood circulation. Reproduced with permission from ¹⁴³, copyright 2017.