Recent advances in multifunctional nanomaterials for photothermal-enhanced Fenton-based chemodynamic tumor therapy

Photothermal (PT)-enhanced Fenton-based chemodynamic therapy (CDT) has attracted a significant amount of research attention over the last five years as a highly effective, safe, and tumor-specific nanomedicine-based therapy. CDT is a new emerging nanocatalyst-based therapeutic strategy for the in situ treatment of tumors via the Fenton reaction or Fenton-like reaction, which has got fast progress in recent years because of its high specificity and activation by endogenous substances. A variety of multifunctional nanomaterials such as metal-, metal oxide-, and metal-sulfide-based nanocatalysts have been designed and constructed to trigger the in situ Fenton or Fenton-like reaction within the tumor microenvironment (TME) to generate highly cytotoxic hydroxyl radicals (•OH), which is highly efficient for the killing of tumor cells. However, research is still required to enhance the curative outcomes and minimize its side effects. Specifically, the therapeutic efficiency of certain CDTs is still hindered by the TME, including low levels of endogenous hydrogen peroxide (H₂O₂), overexpression of reduced glutathione (GSH), and low catalytic efficacy of Fenton or Fenton-like reactions (pH 5.6-6.8), which makes it difficult to completely cure cancer using monotherapy. For this reason, photothermal therapy (PTT) has been utilized in combination with CDT to enhance therapeutic efficacy. More interestingly, tumor heating during PTT not only causes damage to the tumor cells but can also accelerate the generation of •OH via the Fenton and Fenton-like reactions, thus enhancing the CDT efficacy, providing more effective cancer treatment when compared with monotherapy. Currently, synergistic PT-enhanced CDT using multifunctional nanomaterials with both PT and chemodynamic properties has made enormous progress in cancer theranostics. However, there has been no comprehensive review on this subject published to date. In this review, we first summarize the recent progress in PT-enhanced Fenton-based CDT for cancer treatment. We then discuss the potential and challenges in the future development of PT-enhanced Fenton-based nanocatalytic tumor therapy for clinical application.