Nanozymes are nanomaterial-based artificial enzymes. By effectively mimicking catalytic sites of natural enzymes or harboring multivalent elements for reactions, nanozyme systems have successfully served as direct surrogates of traditional enzymes for catalysis. With the rapid development and ever-deepening understanding of nanotechnology, nanozymes offer higher catalytic stability, ease of modification and lower manufacturing cost than protein enzymes. Additionally, nanozymes possess inherent nanomaterial properties, providing not only a simple substitute of enzymes but also a multimodal platform interfacing complex biologic environments. Recent extensive research has focused on designing various nanozyme systems that are responsive to one or multiple substrates by tailored means. Catalytic activities of nanozymes can be regulated by pH, H₂O₂ and glutathione concentrations and levels of oxygenation in different microenvironments. Moreover, nanozymes can be remotely-controlled via different stimuli, including a magnetic field, light, ultrasound, and heat. Collectively, these factors can be adjusted to maximize the diagnostic and therapeutic efficacies of different diseases in biomedical settings. Therefore, by integrating the catalytic property and inherent nanomaterial nature of nanozyme systems, we anticipate that stimuli-responsive nanozymes will open up new horizons for diagnosis, treatment, and theranostics.

This review summarizes the latest progress in deep photodynamic therapy (PDT), which overcomes the Achilles' heel of PDT.

Two-dimensional transition metal carbides and nitrides known as MXenes, with a general formula of M_n+1X_n (n = 1–3), integrate the advantages of metallic conductive transition metals with large groups of carbides, nitrides, or carbonitrides. They have led to a burgeoning research interest in biomedical applications due to their ultrathin structure and fascinating physiochemical (electronic, optical, magnetic, etc.) properties. In this review, we summarize recent advances in biomedical applications for MXenes. We first introduce the preparation methods and surface modifications with respect to MXenes. Their unique properties are then elaborated. Thirdly, we highlight their various biomedical applications, such as with biosensors, antibacterial materials, bioimaging probes, therapeutics, and theranostics. In the end, the current challenges and new opportunities for MXenes in regard to their biomedical applications are also discussed.

Glucose oxidase (GOx) is an endogenous oxido-reductase that is widely distributed in living organisms. Over recent years, GOx has attracted increasing interest in the biomedical field due to its inherent biocompatibility, non-toxicity, and unique catalysis against β-D-glucose. GOx efficiently catalyzes the oxidization of glucose into gluconic acid and hydrogen peroxide (H₂O₂), which can be employed by various biosensors for the detection of cancer biomarkers. Various cancer therapeutic strategies have also been developed based on the catalytic chemistry of GOx: (1) the consumption of glucose provides an alternative strategy for cancer-starvation therapy; (2) the consumption of oxygen increases tumor hypoxia, which can be harnessed for hypoxia-activated therapy; (3) the generation of gluconic acid enhances the acidity of the tumor microenvironment, which can trigger pH-responsive drug release; (4) the generation of H₂O₂ increases the levels of tumor oxidative stress, and the H₂O₂ can be converted into toxic hydroxyl radicals that can kill cancer cells upon exposure to light irradiation or via the Fenton reaction. More importantly, GOx can be combined with other enzymes, hypoxia-activated prodrugs, photosensitizers or Fenton's reagents, to generate multi-modal synergistic cancer therapies based on cancer starvation therapy, hypoxia-activated therapy, oxidation therapy, photodynamic therapy, and/or photothermal therapy. Such multi-modal approaches are anticipated to exert a stronger therapeutic effect than one therapeutic mode alone. Thus, maximizing the potential of GOx in a biomedical context will offer novel clinical solutions to diagnose and treat cancer. In this tutorial review, we introduce the recent advances of GOx in cancer diagnosis and treatment. We then emphasize the design principles and biomedical applications of GOx-based biosensors and cancer therapeutic approaches. Finally, we discuss the challenges and future prospects of GOx-based catalytic systems in biomedicine.