Widespread bacterial resistance induced by the abuse of antibiotics eagerly needs the exploitation of novel antimicrobial agents and strategies. Gold nanoclusters (Au NCs) have recently emerged as an innovative nanomedicine, but study on their antibacterial properties especially toward multidrug resistant (MDR) bacteria is scarce. Herein, we demonstrate that a novel class of Au NCs, mercaptopyrimidine conjugated Au NCs, can act as potent nanoantibiotics targeting these intractable superbugs in vitro and in vivo, without induction of bacterial antibiotic resistance and noticeable cytotoxicity to mammalian cells. The Au NCs kill these superbugs through a combined mechanism including cell membrane destruction, DNA damage, and reactive oxygen species (ROS) generation, and exhibit excellent treatment effects in both macrophages and animal infection models induced by methicillin-resistant Staphylococcus aureus as representative. Moreover, the induction of intracellular ROS production in bacterial cells mainly attributed to the Au NCs' intrinsic oxidase- and peroxidase-like catalytic activities has been demonstrated for the first time.

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Cancer remains one of the most challenging diseases to treat. For accurate cancer diagnosis and targeted therapy, it is important to assess the localization of the affected area of cancers. The general approaches for cancer diagnostics include pathological assessments and imaging. However, these methods only generally assess the tumor area. In this study, by taking advantage of the unique microenvironment of cancers, we effectively utilize in situ self-assembled biosynthetic fluorescent gold nanocluster-DNA (GNC-DNA) complexes to facilitate safe and targeted cancer theranostics. In in vitro and in vivo tumor models, our self-assembling biosynthetic approach allowed for precise bioimaging and inhibited cancer growth after one injection of DNA and gold precursors. These results demonstrate that in situ bioresponsive self-assembling GNC-PTEN (phosphatase and tensin homolog) complexes could be an effective noninvasive technique for accurate cancer bioimaging and treatment, thus providing a safe and promising cancer theranostics platform for cancer therapy.

Cancer treatment has a far greater chance of success if the neoplasm is diagnosed before the onset of metastasis to vital organs. Hence, cancer early diagnosis is extremely important and remains a major challenge in modern therapeutics. In this contribution, facile and new method for rapid multimodal tumor bioimaging is reported by using biosynthesized iron complexes and gold nanoclusters via simple introduction of AuCl and Fe ions. The observations demonstrate that the biosynthesized Au nanoclusters may act as fluorescent and computed tomography probes for cancer bioimaging while the iron complexes behave as effective contrast agent for magnetic resonance imaging. The biosynthesized iron complexes and gold nanoclusters are found biocompatible in vitro (MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay) and in vivo for all the vital organs of circulatory and excretory system. These observations raise the possibility that the biosynthesized probes may find applications in future clinical diagnosis for deep seated early neoplasms by multimodal imaging.

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious superbug that is potentially lifethreatening. Among conventional antibiotics, vancomycin is a "gold standard" agent used to treat serious MRSA infections. Such therapy, however, is often ineffective because of the emergence of less-susceptible strains. Therefore, the exploration of new antimicrobial agents, especially nonantibiotic drugs, to cope with the growing threat of MRSA has become an urgent necessity. Herein, we have investigated the possibility to develop a metallacarborane antimicrobial agent, cobalt bis(1,2-dicarbollide) alkoxy derivative (K121), and we have evaluated the relevant anti-MRSA behaviors. We demonstrated that K121 has a dose-dependent anti-MRSA activity with a low minimal inhibitory concentration of 8 μg/mL and a high selectivity over mammalian cells. In particular, a high bacteria-killing efficiency was observed with eradication of all MRSA cells within 30 min. In addition, K121 showed a high inhibition effect on the formation of bacterial biofilm. More importantly, unlike vancomycin, a repeated use of K121 would not induce drug resistance even after 20 passages of MRSA. The mechanistic study showed that K121 kills MRSA by inducing an increase in the reactive oxygen species (ROS) production and consequentially inducing irreversible damage to the cell wall/ membrane, which ultimately leads to the death of MRSA. Our results suggested that K121 may be used as a promising nonantibiotic therapeutic agent against MRSA infections in future clinical practices.