Catalase-Like Nanozymes and Their Applications in Alleviating Tumor Hypoxia for the Therapeutic Enhancement

Cancer has been globally acknowledged as one of the most dangerous health problems. Although current therapies have shown promising results, they cannot eliminate all tumor cells and prevent the recurrence of these cells in the long term. The aggressive progress of a tumor can be triggered when the cancer is suffered from oxygen depletion or so-called hypoxia. Previously, researchers primarily utilized catalase's enzymatic activity to convert the endogenous hydrogen peroxide in cancer cells into oxygen, alleviating intracellular hypoxia. However, using natural enzymes has faced limitations, such as low stability and uneasy and costly production, making it hard to commercialize this method. To tackle the problem, synthetic nanomaterials, which could mimic enzyme-like activity, are utilized and named nanozyme. The ability of nanozymes mostly comes from the redox reaction of cations of high-Z metals, such as manganese, iron, cerium, and iridium. This review will offer readers an overview of the synergistic effect of nanozyme-based delivery models with the ability to generate oxygen to attenuate tumor hypoxia and enhance the therapeutic outcome. Based on the literature search, each type of nanozymes possesses both pros and cons; however, they all perform well in suppressing tumor hypoxia and improving therapeutic efficacy. Though, more studies must be conducted to guarantee these catalase-mimicking nanozymes’ long-term safety before the clinical application. Besides, solving the problem of hypoxia also opens up new paths for potential applications in 3D in-vitro cancer cell culture.