Figure 1.

Schematic illustration of the hypoxia-degradable poly(phosphorylcholine)-based (^HPMPC) nanogel for tumor drug delivery. ^HPMPC nanogel shows ultra-long blood circulation without causing the accelerated blood clearance phenomenon, which leads to the enhanced accumulation in tumor tissue. ^HPMPC nanogel holds the loaded drug firmly in blood or normal tissue whereas releases the drug effectively in tumor hypoxic environment, leading in improved therapeutic effect and negligible side effects.