dChan - Q Origins Project Archive

Silver Nanoparticles as Potential Antiviral Agents

2.6. Poxviridae

Monkeypox virus (MPV), an orthopoxvirus similar to variola virus, is the causative agent of monkeypox in many species of non-human primates, but it is also a human pathogen with a clinical presentation similar to that of smallpox. MPV is considered a big threat to human life and therefore research is being carried out to develop drugs and therapeutic agents against this virus [74].

Different size nanoparticles were produced by plasma gas synthesis and used by Rogers et al. [45] in a plaque reduction assay of MPV. The silver nanoparticles used in this work were 25 (Ag-NP-25), 55 (Ag-NP-55) and 80 (Ag-NP-80) nm, and some nanoparticles were also coated with polysaccharide, 10 (Ag-PS-10), 25 (Ag-PS-25) and 80 (Ag-PS-80) nm nanoparticles. These nanoparticles, at concentrations ranging from 12.5 to 100 μg/mL, were evaluated for MPV inhibitory efficacy using a plaque reduction assay. The main results showed that the Ag-PS-25 (polysaccharide-coated, 25 nm) and Ag-NP-55 (non-coated, 55 nm) exerted a significant dose-dependent inhibition of MPV plaque formation, but the mechanism by which this inhibition occurs has not been further investigated. Poxviruses enter cells by endocytosis or direct fusion at the plasma membrane, and at least 9 or 10 envelope proteins are involved in the entry mechanism, this is followed by a regulated sequence of events that allow virus replication. Many steps in the virus life cycle are still unknown, and this report on the activity of silver nanoparticles is too preliminary to attempt to give a satisfactory explanation of their mechanism of action. Probably the silver nanoparticles may intervene in the early steps of binding and penetration by blocking virus-host cell binding by physical obstruction or, if internalised, they can disrupt intracellular pathways important for virus replication.

Rogers et al. [45] also described that AgNO3 was active as a MPV inhibitor, but at the concentration of 100 µg/mL its toxic effect on Vero cells impeded the evaluation of the antiviral activity. Interestingly, some of the nanoparticles analysed in the study promoted an increase in the mean number of MPV plaques/well at the highest concentrations used. A potential explanation for these contrasting results could lie in the fact that nanoparticles may tend to aggregate and consequently create on cells areas available for increased contacts between viral particles and the cell membrane, therefore augmenting internalization and plaque formation. However, these data are preliminary and need a more in-depth analysis to draw more significant conclusions.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264685/