# Metal Nanozymes: New Horizons in Cellular Homeostasis Regulation
## 8 Metal Nanozymes in Cancer Treatment
In addition, the ferritin nanozyme diagnostic technique is simple, rapid, and economical. This method simplifies the conventional immunohistochemical experiment for tumor detection and shortens the testing time from 4 to 1 h.  
[PERSON] et al. [14] reported that magnetite nanoparticles (Fe\({}_{3}\)O\({}_{4}\)) possess an intrinsic enzyme mimetic activity similar to that found in natural peroxididases and developed two immunoassay using the intrinsic dual functionality of the Fe\({}_{3}\)O\({}_{4}\) MNPs as a peroxidase and magnetic separator. Metal-based and metal-organic-based nanozymes are not the only ones applied for cancer diagnosis. [PERSON] et al. underline that early cancer diagnosis is the key to improving patient survival rate [220] and point out that metal-organic frameworks (MOFs) consist of infinite crystalline lattices with metal clusters and organic linkers may provide opportunities for detection of cancer cells which has remained unknown. They reported the successful use of Fe-MIL-101 MOF with intrinsic peroxidase-like to detect cancer cells by conjugating folic acid onto Fe-MIL-101 without any surface modification. Furthermore, the authors found that the Fe-MIL-101-FA bound selectively to the target cells (human cervical carcinoma cells (Hela), colon adenocarcinoma cells (HT-29), and human mouth epidermal carcinoma cells (KB)) through the interaction between FA and folate receptor. Correspondingly, [PERSON] et al. used MOF as an exemplary model of oxygen catalyzer because of their rich catalytic site and sensitizing effect due to the presence of radiosensitizer (high-Z element Hf) in their structural array [221] (Figure 7). The authors designed a folic acid-modified enzyme-like hafnium-based manganoporphyrin metal-organic framework nanoparticles (MnTCP-Hf-FA MOF NPs) to overcome hypoxia-induced radioresistance and prevent a postoperative recurrence. The MOF NPs they proposed increased radiotherapy's therapeutic efficiency and significantly decreased the risk of local tumor recurrence inside a solid tumor with an inadequate oxygen supply. In vivo experiments revealed that the MnTCP-Hf-FA MOF NPs could effectively inhibit melanoma growth and prevent tumor postoperative recurrence with only one X-ray irradiation after intravenous injection. Figure 7: Schematic illustrations of the process for synthesizing nanosensitizer (**a**) and the representation of systemic and intracellular pathways and the action of nanosensitizer (**b**). Reproduced from Reference [221] with permission from the Royal Society of Chemistry. The presented study revealed that MOF NPs could be used not only for cancer diagnosis but also for cancer therapy, especially when radiosensitizers are at MOF NPs. The additional value of combining X-ray irradiation with MOF-NP joined with radiosensitizer and prospects is a versatile approach to solving hypoxic tumors' critical radiosistance issue [222]. [PERSON], [PERSON] et al. [223] constructed a nanozyme with dual enzyme-like activities (PtFe@Fe3O4) for highly efficient tumor catalytic therapy in response to the TME, which is generally known to feature unique characteristics such as the mildly acidic nature, hypoxia, and overproduced hydrogen peroxide (H2O2). Serving as an H2O2-responsive nanozyme, PtFe@Fe3O4 exhibited both intrinsic POD-like and CAT-like activities under acidic conditions. On the other hand, due to the reduced H2O2 concentration in TME, the effect of single-nanozyme-based catalytic therapy is not competent enough compared with combination therapy. The authors have shown that it is possible to achieve efficient deep pancreatic cancer therapy by combining photothermal effects. The catalytic activities of PtFe@Fe3O4 and their therapeutic effect were significantly enhanced under the irradiation of the near-infrared (NIR) laser. At the same time, under light irradiation, nanocatalysts could promote ROS production by direct electron transfer and photoenhanced Fenton reaction [223], (Figure 8).