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In this study, we investigated whether ZnO coating on Ag nanoparticles (NPs) tunes electron flux and hole figuration at the metal-semiconductor interface under UV radiation. This effect triggers the photoactivity and generation of reactive oxygen species from Ag@ZnO NPs, which results in enhanced cytotoxic effects and apoptotic cell death in human breast cancer cells (MDA-MB231). In this context, upregulation of apoptotic cascade proteins (i.e., Bax/Bcl2 association, p53, cytochrome c, and caspase-3) along with activation of oxidative stress proteins suggested the occurrence of apoptosis by Ag@ZnO NPs in cancer cells through the mitochondrial pathway. Also, preincubation of breast cancer cells with Ag@ZnO NPs in dark conditions muted NP-related toxic effects and consequent apoptotic fate, highlighting biocompatible properties of unexcited Ag@ZnO NPs. Furthermore, the diagnostic efficacy of Ag@ZnO NPs as computed tomography (CT)/optical nanoprobes was investigated. Results confirmed the efficacy of the photoactivated system in obtaining desirable outcomes from CT/optical imaging, which represents novel theranostic NPs for simultaneous imaging and treatment of cancer.

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Highly resistant pathogens may be developed in patients with immune disorders after prolonged exposure to antibiotics, a growing threat worldwide. In order to overcome these problems, this study introduces a new class of engineered nanosystems comprising of tea tree oil nanoemulsion (TTO NE) loaded with Ag nanoparticles (NPs). Silver shows a strong toxicity towards a wide range of microorganisms. Also, TTO NE could be employed as a promising and safe antimicrobial agent for local therapies of bacterial infections. The nanosystem was prepared by low-energy method. Mean droplet size of the NE was found to be 17.7 nm. Results of the antibacterial assays showed promising ability of the designed nanosystem for eradication of Gram-positive and Gram-negative bacteria (95%). Also, it was shown that introducing colloidal Ag NPs to the TTO NE exerted a synergistic effect against Escherichia coli (FIC 0.48) while only an additive effect was observed against Staphylococcus aureus (FIC 0.75). The antibacterial effects of TTO NE+Ag NPs together with their compatibility with human cells can present them as a suitable candidate to fight against the antibacterial resistance threat.