OPEN ACCESS ARTICLE – Early Stages of Antibacterial Damage of Metallic Nanoparticles by TEM and STEM-HAADF – Current Nanoscience

Journal: Current Nanoscience

Author(s): Beatriz Liliana Espana-Sanchez, Carlos Alberto Avila-Orta, Luis Felipe Padilla-Vaca, Enrique Diaz Barriga-Castro, Florentino Soriano-Corral, Pablo Gonzalez-Morones, Diana Guadalupe Ramirez-Wong, Gabriel Luna-Barcenas

Graphical Abstract:



Background: Propagation of pathogens has considered an important health care problem due to their resistance against conventional antibiotics. The recent challenge involves the design of functional alternatives such as nanomaterials, used as antibacterial agents. Early stages of antibacterial damage caused by metallic nanoparticles (NPs) were studied by Transmission Electron Microscopy (TEM) and combined Scanning Transmission Electron Microscopy with High Angle Annular Dark Field (STEM-HAADF), aiming to contribute to the elucidation of the primary antibacterial mechanism of metallic NPs.

Methods: We analyze the NPs morphology by TEM and their antibacterial activity (AA) with different amounts of Ag and Cu NPs. Cultured P. aeruginosa were interacted with both NPs and processed by TEM imaging to determine NPs adhesion into bacteria wall. Samples were analyzed by combined STEM-HAADF to determine the NPs penetration into bacterium and elemental mapping were done.

Results: Both NPs displays AA depending on NPs concentration. TEM images show NPs adhesion on bacterial cells, which produces morphological changes in the structure of the bacteria. STEMHAADF also proves the NPs adhesion and penetration by intracellular localization, detecting Ag/Cu species analyzed by elemental mapping. Moreover, the relative amount of phosphorus (P) and sulfur (S) increases slightly in P. aeruginosa with the presence of NPs. These elements are associated with damaged proteins of the outer cell membrane.

Conclusions: Combined microscopy analyses suggest that the early stages of antibacterial damage caused by alteration of bacterial cell wall, and can be considered a powerful tool aiming to understand the primary antibacterial mechanism of NPs.

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Press Release for EurekAlert! Probiotics: Novel biosynthetic tool to develop metallic nanoparticles

This research article by Dr. Nida Akhtar et al has been published in Recent Patents on Drug Delivery & Formulation, Volume 11, Issue 1, 2017


Probiotics, being live microbes, exert numerous beneficial health effects on the host cells. Such probiotics are commercially available as dietary supplements, foods, pharmaceutical formulations. Yakult, Activia yogurt, DanActive fermented milk provide health benefits like boosting up the immune system, treating digestive problems, mental illness, neurological disorders, cancer, etc. However, the use of probiotic bacteria to develop metallic nanoparticles (MNPs) constitutes novel research nowadays. Research inputs and patent reports according to an article published in the journal Recent Patents on Drug Delivery and Formulation highlight their potential in the field of cosmetics, pharmaceuticals, medicine and biotechnology as well.

Prof. Kamla Pathak, the corresponding author said: “Our review findings reinstate the potential of probiotic bacteria to produce MNPs. Patents (US, EP and WIPO patents) during 2009-2016 reaffirm the research and inspire the scientific community worldwide for future exploration. This is the first review article in this aspect that systematically tracks the intellectual aspects of applications and synthesis of MNPs by probiotic bacteria. Prof. Pathak said, “Our study details the interventions on which research on MNPs is on. Gold, silver, magnetic, selenium, iron oxide, magnetic-optical iron oxide-gold core-shell, magnesium oxide, copper oxide, aluminum oxide, titanium dioxide, zinc oxide nanoparticles have applications ranging from their usage in analytical methodologies to treat and diagnose diseases. Specifically, gold NPs are suggested for drug delivery and treating lymphocytic leukemia; silver and copper NPs for antimicrobial activity and zinc oxide NPs as anti-corrosive, antifungal and as an additive in food products such as breakfast cereals. These NPs need to be explored more as no patent till date was found on them based on their biosynthesis, according to the author’s report.

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