NIR-II-driven and glutathione depletion-enhanced hypoxia-irrelevant free radical nanogenerator for combined cancer therapy

Background: Though the combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) appears to be very attractive in cancer treatment, hypoxia and overproduced glutathione (GSH) in the tumor microenvironment (TME) limit their efficacy for further application. Results: In this work, a smart hypoxia-irrelevant free radical nanogenerator (AIPH/PDA@CuS/ZIF-8, denoted as APCZ) was synthesized in situ via coating copper sulphide (CuS)-embedded zeolitic imidazolate framework-8 (ZIF-8) on the free radical initiator 2,2'-azobis[2-(2-imidazolin-2-yl)propane]-dihydrochloride (AIPH)-loaded polydopamine (PDA). APCZ showed promising GSH-depleting ability and near-infrared (NIR)-II photothermal performance for combined cancer therapy. Once internalized by 4T1 cells, the outer ZIF-8 was rapidly degraded to trigger the release of CuS nanoparticles (NPs), which could react with local GSH and sequentially hydrogen peroxide (H2O2) to form hydroxyl radical (center dot OH) for CDT. More importantly, the hyperthermia generated by APCZ upon 1064 nm laser excitation not only permitted NIR-II photothermal therapy (PTT) and promoted CDT, but also triggered the decomposition of AIPH to give toxic alkyl radical (center dot R) for oxygen-independent PDT. Besides, the PDA together with CuS greatly decreased the GSH level and resulted in significantly enhanced PDT/CDT in both normoxic and hypoxic conditions. The tumors could be completely eradicated after 14 days of treatment due to the prominent therapeutic effects of PTT/PDT/CDT. Additionally, the feasibility of APCZ as a photoacoustic (PA) imaging contrast agent was also demonstrated. Conclusions: The novel APCZ could realize the cooperative amplification effect of free radicals-based therapies by NIR-II light excitation and GSH consumption, and act as a contrast agent to improve PA imaging, holding tremendous potential for efficient diagnosis and treatment of deep-seated and hypoxic tumors.

Automated summary

The novel smart nanogenerator APCZ was synthesized for combined cancer therapy, showing promising GSH-depleting ability and photothermal performance. By releasing CuS nanoparticles in situ, it achieved chemodynamic therapy and also allowed for photodynamic therapy through decomposition of AIPH. With enhanced therapeutic effects in both hypoxic and normoxic conditions, complete eradication of tumors was achieved after 14 days of treatment. Additionally, APCZ demonstrated feasibility as a contrast agent for photoacoustic imaging, showcasing its potential for efficient diagnosis and treatment of deep-seated and hypoxic tumors.