Metallic Structures: Effective Agents to Fight Pathogenic Microorganisms

Abstract

The current worldwide pandemic caused by coronavirus disease 2019 (COVID-19) had alerted the population to the risk that small microorganisms can create for humankind's wellbeing and survival. All of us have been affected, directly or indirectly, by this situation, and scientists all over the world have been trying to find solutions to fight this virus by killing it or by stop/decrease its spread rate. Numerous kinds of microorganisms have been occasionally created panic in world history, and several solutions have been proposed to stop their spread. Among the most studied antimicrobial solutions, are metals (of different kinds and applied in different formats). In this regard, this review aims to present a recent and comprehensive demonstration of the state-of-the-art in the use of metals, as well as their mechanisms, to fight different pathogens, such as viruses, bacteria, and fungi.

Keywords: antimicrobial agents; bacteria; fungi; metals; virus.

Figure 1

Representative mechanism of the antiviral properties of Au-NPs. On the left, a normal mechanism by which a virus infects a host cell (in this case, a eukaryotic cell) can be seen: firstly, viral attachment to the cell membrane occurs, followed by penetration into the cytoplasm; then the virus proceeds to use the cellular mechanisms to replicate its genetical material, generating virions to continue the infectious cycle. On the right, is shown a mechanism of inhibition by which Au-NPs can intervene, either by attaching themselves to the virus, blocking its attachment to the cell and consequent entry in the cell and ultimately interfering with the mechanisms of viral replication inside the cell (adapted from [88]).

Figure 2

Representative illustration of the interaction between antibiotics and Ag-NPs and their combined action inside both Gram-negative (left) and Gram-positive (right) bacteria. Although there is a thicker path for Ag-NPs and antibiotics to travel through with the Gram-negative bacteria membrane, once, inside the cell, the mechanisms are the same as for Gram-positive bacteria: accumulation of particles inside the cell; production of ROS; and ultimately cell death by damaging the bacterial DNA (adapted from [111]).