Single-Atom Nanoenzyme-Based Autoluminescence System for Cancer Cell Imaging and Mitochondrial-Targeted Therapy

Thermoresponsive and Substrate Self-Cycling Nanoenzyme System for Efficient Tumor Therapy

Cerium oxide (CeO2-x) performs well in photothermal and catalytic properties due to its abundance of oxygen vacancies. Based on this, we designed a thermosensitive therapeutic nanoplatform to achieve continuous circular drug release in tumor. It can solve the limitation caused by insufficient substrate in the process of tumor treatment. Briefly, CeO2-x and camptothecin (CPT) were wrapped in an agarose hydrogel, which could be melted by the photothermal effect of CeO2-x. At the same time, the local temperature increase provided photothermal treatment, which could induce the apoptosis of tumor cell. After that, CPT was released to damage the DNA in tumor cells to realize chemical treatment. In addition, CPT could active nicotinamide adenine dinucleotide oxidase to react with O2 to increase the intracellular H2O2. After that, the exposed CeO2-x could catalyze H2O2 to generate cytotoxic reactive oxygen species for chemodynamic therapy. More importantly, CeO2-x could catalyze H2O2 to produce O2, which could combine with the catalytic action of CPT to construct a substrate self-cycling nanoenzyme system. Overall, this self-cycling nanoplatform released hypoxia in the tumor microenvironment and built a multimode tumor treatment, which achieved an ideal antitumor affect.

Antioxidant curcumin induces oxidative stress to kill tumor cells (Review)

Curcumin is a plant polyphenol in turmeric root and a potent antioxidant. It binds to antioxidant response elements for gene regulation by nuclear factor erythroid 2-related factor 2, thereby suppressing reactive oxygen species (ROS) and exerting anti-inflammatory, anti-infective and other pharmacological effects. Of note, curcumin induces oxidative stress in tumors. It binds to several enzymes in tumors, such as carbonyl reductases, glutathione S-transferase P1 and nicotinamide adenine dinucleotide phosphate to induce mitochondrial damage, increase ROS production and ultimately induce tumor cell death. However, the instability and poor pharmacokinetic profile of curcumin in vivo limit its clinical application. Therefore, the effects of curcumin in vivo may be enhanced through its combination with drugs, derivative development and nanocarriers. In the present review, the mechanisms of curcumin that induce tumor cell death through oxidative stress are discussed. In addition, the methods used to enhance the antitumor activity of curcumin are described. Finally, the existing knowledge on the functions of curcumin in tumors, particularly in terms of oxidative stress, are summarized to facilitate future curcumin research.