Positive feedback nanoamplifier responded to tumor microenvironments for self-enhanced tumor imaging and therapy.

Targeted activation or enhancement is an attractive strategy in the design of nano-theranostics. However, the responsiveness of the nanoagents is restricted by the limited levels of intra-tumor stimuli. Herein, we constructed a positive feedback nanoamplifier by encapsulating glucose oxidase (GOx) in the ferric ions contained metal organic framework (MIL-100), and coating the nanoparticles with polydopamine modified hyaluronic acid (HA-PDA). The mechanism of action of the ensuing nanoamplifiers was three pronged: 1) the high intra-tumor acidity accelerated the release of GOx, which consumed endogenous glucose and "starved" the tumors, in addition to aggravating the local acidity and H2O2 levels; 2) the hydroxyl radicals (·OH) generated from the Fenton-like reaction between MIL-100 with H2O2 contributed to the chemodynamic tumor therapy and augmented the O2 microenvironment, which could be speeded up under acid condition; 3) the oxygen (O2) produced in the Fenton-like reaction relieved the intra-tumor hypoxia and ensured the enzymatic reaction of GOx, along with augmenting the photoacoustic signal of nanoamplifier. Preliminary experiments in tumor bearing mice showed that the nanoamplifier not only boosted the local acidity/H2O2/O2 levels in tumor site to successfully suppress the growth of tumors through the self-enhanced chemodynamic/starving therapy, but also achieved the photoacoustic imaging of tumors. Taken together, this novel nanoamplifier with the abilities of self-enhanced tumor imaging and therapy is a promising entrant in the field of anti-tumor theranostics.