It is known that the main-group metals and their related materials show poor catalytic activity due to a broadened single resonance derived from the interaction of valence orbitals of adsorbates with the broad sp-band of main-group metals. However, Mg cofactors existing in enzymes are extremely active in biochemical reactions. Our density function theory calculations reveal that the catalytic activity of the main-group metals (Mg, Al and Ca) in oxygen reduction reaction is severely hampered by the tight-bonding of active centers with hydroxyl group intermediate, while the Mg atom coordinated to two nitrogen atoms has the nearoptimal adsorption strength with intermediate oxygen species by the rise of p-band center position compared to other coordination environments. We experimentally demonstrate that the atomically dispersed Mg cofactors incorporated within graphene framework exhibits a strikingly high half-wave potential of 910 mV in alkaline media, turning a s/p-band metal into a highly active electrocatalyst.

Photodynamic therapy (PDT), a wellknown clinical modality that involves photosensitizer, molecular oxygen (O 2 ), and excitation light to generate cytotoxic reactive oxygen species such as singlet oxygen ( 1 O 2 ), has been proven to be a selective method for treating a wide spectrum of localized and superficial cancers or other diseases. [1][2][3][4][5][6][7][8][9] In addition to destroying cancer cells through direct photodamage, PDT can also induce vascular damage in the tumor, and activate the response of immune system. [10][11][12][13] Possessing spatial and temporal control over the localization of the light irradiation, the O 2 -involved PDT can remarkably improve the selectivity and reduce the side effects when compared to other conventional modalities such as chemotherapy, surgery, and radiotherapy. [14][15][16] On the other hand, tumor hypoxia compromises therapeutic effect of PDT, as O 2 is an indispensable element during the process. Uncontrollable growth of tumor cells as well as dysregulated formation of tumor blood vessels inevitably result in the cancer hypoxia. [17,18] In addition, microvascular collapse caused by PDT would further compromise the O 2 supply and aggravate the hypoxia condition, thus preventing effective PDT of cancer. Consequently, a vicious circle occurs, as PDT not only consumes localized O 2 , but also cuts off the O 2 supply. [19][20][21] To date, three main strategies have been employed to overcome the pre-existing hypoxia and improve the therapeutic effect of PDT. The most popular approach relies on the integration of PDT with other therapeutic modalities for a synergistic therapy. [17,22,23] However, such complex structures are often costly, which limit their scalable production and reproducibility. Another strategy is the utilization of intelligent nanomaterials that can act as O 2 carriers for direct transportation of mole cular oxygen to tumor sites. For example, Hu and coworkers reported photosensitizer-loaded perfluorocarbon nanodroplets as an O 2 self-enriched PDT nanoplatform. [24] The last approach is to construct smart nanoplatforms for in situ generation of O 2 within solid tumors based on the characteristics Tumor hypoxia compromises the therapeutic efficiency of photodynamic therapy (PDT) as the local oxygen concentration plays an important role in the generation of cytotoxic singlet oxygen ( 1 O 2 ). Herein, a versatile mesoporous nanoenzyme (NE) derived from metal-organic frameworks (MOFs) is presented for in situ generation of endogenous O 2 to enhancethe PDT efficacy under bioimaging guidance. The mesoporous NE is constructed by first coating a manganese-based MOFs with mesoporous silica, followed by a facile annealing process under the ambient atmosphere. After removing the mesoporous silica shell and post-modifying with polydopamine and poly(ethylene glycol) for improving the biocompatibility, the obtained mesoporous NE is loaded with chlorin e6 (Ce6), a commonly used photosensitizer in PDT, with a high loading capacity. Upon the O 2 generation through the...

Image-guided photothermal therapy (PTT) is an attractive strategy to improve the diagnosis accuracy and treatment outcomes by monitoring the accumulation of photothermal agents in tumors in real-time and determining the best treatment window. Taking advantage of the superior imaging quality of NIR-II fluorescence imaging and remote-controllable phototherapy modality of PTT, we developed a facile macromolecular fluorophore (PF) by conjugating a small-molecule NIR-II fluorophore (Flav7) with an amphiphilic polypeptide. The PF can form uniform micelles in aqueous solution, which exhibit a slight negative charge. In vitro experimental results showed that the PF nanoparticles showed satisfactory photophysical properties, prominent photothermal conversion efficiency (42.3%), excellent photothermal stability, negligible cytotoxicity, and photothermal toxicity. Meanwhile, the PF can visualize and feature the tumors by NIR-II fluorescence imaging owing to prolonged blood circulation time and enhanced accumulation in tumors. Moreover, in vivo studies revealed that the PF nanoparticles achieved an excellent photothermal ablation effect on tumors with a low dose of NIR-II dye and light irradiation, and the process can be traced by NIR fluorescence imaging.