DNA molecules are attached onto carboxylate-terminated alkanethiol self-assembled monolayers (SAMs) preformed at gold surfaces via the N-hydroxysulfosuccinimide (NHS)/1-(3-(dimethylamino)propyl)-3ethylcarbodiimide hydrochloride (EDC) cross-linking reaction. Cyclic voltammetry, quartz crystal microbalance (QCM), and atomic force microscopy (AFM) were used to probe the surface coverage and molecular orientation of the immobilized DNA molecules. The DNA attachment is attributed to the formation of amide bond between the carboxylate groups and the amino groups on the DNA bases since the possibility of nonspecific adsorption of DNA onto preformed SAMs or NHS ester monolayers was studied and excluded. Our voltammetric results indicate a significant blockage of the sites originally available in the alkanethiol SAMs for facile heterogeneous electron transfer by the attached DNA molecules. QCM provided a semiquantitative measurement of the amount of immobilized DNA. The AFM images, for the first time, revealed that relatively ordered DNA films can be formed in the covalent attachment with DNA molecules stretched by the underlying terminal carboxylate groups of the SAMs. However, certain fragmentation appears to have occurred upon immobilization. The fragmentation is probably due to the strong interaction between the DNA molecules and the carboxylate groups whose spatial distribution does not fit perfectly well with the separation and distribution of the amino groups on the bases within the DNA double helix.

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Nanozyme‐based chemodynamic therapy (CDT) for fighting bacterial infections faces several major obstacles including low hydrogen peroxide (H2O2) level, over‐expressed glutathione (GSH) in infected sites, and inevitable damage to healthy tissue with abundant nonlocalized nanozymes. Herein, a smart ultrasmall Fe3O4‐decorated polydopamine (PDA/Fe3O4) hybrid nanozyme is demonstrated that continuously converts oxygen into highly toxic hydroxyl radical (•OH) via GSH‐depleted cascade redox reactions for CDT‐mediated bacterial elimination and intensive wound disinfection. In this system, photonic hyperthermia of PDA/Fe3O4 nanozymes can not only directly damage bacteria, but also improve the horseradish peroxidase‐like activity of Fe3O4 decorated for CDT. Surprisingly, through photothermal‐enhanced cascade catalytic reactions, PDA/Fe3O4 nanozymes can consume endogenous GSH for disrupting cellular redox homeostasis and simultaneously provide abundant H2O2 for improving •OH generation, ultimately enhancing the antibacterial performance of CDT. Such PDA/Fe3O4 can bind with bacterial cells, and reveals excellent antibacterial property against both Staphylococcus aureus and Escherichia coli. Most interestingly, PDA/Fe3O4 nanozymes can be strongly retained in infected sites by an external magnet for localized long‐term in vivo CDT and show minimal toxicity to healthy tissues and organs. This work presents an effective strategy to magnetically retain the therapeutic nanozymes in infected sites for highly efficient CDT with good biosafety.

Combined therapeutic strategies for bacterial infection have attracted worldwide attention owing to their faster and more effective therapy with fewer side effects compared with monotherapy. In this work, gold–platinum nanodots (AuPtNDs) are simply and quickly synthesized by a one-step method. They not only exhibit powerful peroxidase-like activity but also confer a higher affinity for hydrogen peroxide (H2O2), which is 3.4 times that of horseradish peroxidase. Under 808 nm laser irradiation, AuPtNDs also have excellent photothermal conversion efficiency (50.53%) and strong photothermal stability. Excitingly, they can combat bacterial infection through the combination of chemodynamic and photothermal therapy. In vitro antibacterial results show that the combined antibacterial strategy has a broad-spectrum antibacterial property against both Escherichia coli (Gram negative, 97.1%) and Staphylococcus aureus (Gram positive, 99.3%). Animal experiments further show that nanodots can effectively promote the healing of bacterial infection wounds. In addition, owing to good biocompatibility and low toxicity, they are hardly traceable in the main organs of mice, which indicates that they can be well excreted through metabolism. These results reveal the application potential of AuPtNDs as a simple and magic multifunctional nanoparticle in antibacterial therapy and open up new applications for clinical anti-infective therapy in the near future.