Recently, nanomaterials with intrinsic enzyme-like activity, referred to as nanozymes, have drawn substantial research interest [
10-
12]. Since the intrinsic peroxidase-like activity of Fe
3O
4 magnetic nanoparticles was reported by Yan's group in 2007, numerous advanced nanomaterials with intrinsic enzyme-like catalytic activity are mushrooming [
13-
15]. Due to the advantages of robust catalytic activity, high stability, low cost, as well as facile synthesis, nanozyme has emerging as a promising alternative to natural enzyme [
16-
18]. In the past years, nanozymes have found very wide applications in the field of biomedicine, biosensing and bioimaging [
19-
23]. With the continuous advances in nanotechnology, the biomedical application of nanozymes is still in the ascendant. In particular, the development of nanozymes that possess high stability and good biocompatibility
in vivo brings a new opportunity for the theranostic applications [
24,
25]. It is not difficult to imagine that prodrug activation mediated by nanozyme also can be employed for the site-specific drug synthesis, thus achieving localized therapeutic effect. Indeed, many nanozyme-activated prodrug strategies have been developed for targeted therapy, referred to as nanozyme-activating prodrug therapies [
26-
32]. As shown in
Fig. 1, nontoxic prodrugs can be effectively converted into toxic drugs under the activation of nanozymes, thus leading to cell death. These nanozyme-activated prodrug strategies combine the advantages of EPT (enhanced therapeutic efficacies as well as low off-target effects) and nanozyme (robust catalytic activity and good stability), which showed great potential in the field of targeted therapy [
26]. Currently, researches on nanozyme-activating prodrug therapy are still in its initial stage [
33]. The combinations of enzyme/prodrug used in the EPT strategies should be good references for developing novel nanozyme-activated prodrug strategies [
5,
34]. It is undeniable that the development of nanozymes has made very significant progress, however, nanozymes that used in the nanozyme-activating prodrug therapy are mostly focused on mimicking oxidoreductases (
e.g., peroxidase, oxidase, and nitroreductase) and hydrolases (
e.g., phosphatase, glucuronidase, and glycosidases), this range is only humble at the very best [
27,
28]. Thus, more advanced nanozymes with diverse catalytic activities, high stability, good biocompatibility, as well as excellent capability of navigating them to the desired action site should be developed. What is more, it is universally acknowledged that the long-term biological safety should be the first consideration for the use of nanomaterials
in vivo [
35,
36]. At present, most nanozymes used in the nanozyme-activating prodrug therapy are metal-containing. However, most of metal- or metal oxide-based nanozymes are very susceptible to destabilizing oxidation under acidic conditions, whose
in vivo applications are often limited by the potential metal toxicity [
37-
39]. In the future, nanozymes with relatively excellent biological safety should be developed, which may be more desirable in the development of nanozyme-activated prodrug strategies. In addition, identification of substrate scopes of the corresponding nanozyme is also of great importance in designing novel benign prodrugs for successful "nanozyme prodrug therapies" [
33].