Silver nanoparticles are broad-spectrum bactericidal and virucidal compounds

Abstract

The advance in nanotechnology has enabled us to utilize particles in the size of the nanoscale. This has created new therapeutic horizons, and in the case of silver, the currently available data only reveals the surface of the potential benefits and the wide range of applications. Interactions between viral biomolecules and silver nanoparticles suggest that the use of nanosystems may contribute importantly for the enhancement of current prevention of infection and antiviral therapies. Recently, it has been suggested that silver nanoparticles (AgNPs) bind with external membrane of lipid enveloped virus to prevent the infection. Nevertheless, the interaction of AgNPs with viruses is a largely unexplored field. AgNPs has been studied particularly on HIV where it was demonstrated the mechanism of antiviral action of the nanoparticles as well as the inhibition the transmission of HIV-1 infection in human cervix organ culture. This review discusses recent advances in the understanding of the biocidal mechanisms of action of silver Nanoparticles.

Figure 1

Transmission electron microscopy (TEM) images of silver nanoparticles with diameters of 20 nm (Aldrich), 60 nm (Aldrich), and 100 nm (Aldrich), respectively. Scale bars are 50 nm.

Figure 2

Time-of-addition experiment. HeLa-CD4-LTR-β-gal cells were infected with HIV-1_IIIB and exposed to silver nanoparticles (1 mg/mL). Different antiretrovirals were added at different times post infection. Activity of silver nanoparticles was compared with (A) fusion inhibitor (Tak-779, 2 μM), (B) RT inhibitor (AZT, 20 μM), (C) protease inhibitor (Indinavir, 0.25 μM), and (D) integrase inhibitor (118-D-24, 100 μM). Dashed lines indicate the moment when the activity of the silver nanoparticles and the antiretroviral differ. The assays were performed in triplicate; the data points represent the mean and the colored lines are nonlinear regression curves performed with SigmaPlot 10.0 software. http://www.jnanobiotechnology.com/content/8/1/1/figure/F2

Figure 3

Human cervical culture model. a) To rule out possible leaks in the agarose seal, Dextran blue was added to the upper chamber on day 6 of the culture. Its presence in the lower chamber was determined 20 h later to all Transwells used in the experiments, along with the negative control well with agarose only, b) the other negative control alone, with tissue and virus but without treatment or challenge and c) positive control well with tissue alone, infected with only the HIV-1 virus. d) Inhibition of HIV-1 transmission; the cervical tissue was treated with PVP-coated AgNPs at different concentrations in a Replens gel or RPMI + 10% FCS media, which was then infected with HIV-1_IIIB. HIV transmission or inhibition of transmission across the mucosa was determined in the lower chamber by formation of syncytia using indicator cells (MT-2). http://www.jnanobiotechnology.com/content/8/1/15/figure/F3

Figure 4

Protection from HIV-1 infection following pre-treatment of the cervical explant with PVP-coated AgNPs. a) Cervical explants were exposed to 0.1 or 0.15 mg/mL PVP-coated AgNPs in RPMI + 10% FCS media for 20 minutes. After thoroughly washing extracellular PVP-coated AgNPs from the cervical explant, and after 1 minute, 24 h, 48 h and 72 h, cell-free virus (HIV-1_IIIB) [(5 × 10⁵ TCID₅₀)] was added to the upper chamber. To verify the neutralization of HIV-1 transmission, we cultured the indicator cells (MT-2) in the lower chamber and evaluated the inhibition of the HIV-1 infection. b) Cervical explants were exposed to HIV-1 in the absence of PVP-coated AgNPs as a control and to 0.1 or 0.15 mg/mL of PVP-coated AgNPs as pretreatment. Graphs show values of the means ± standard deviations from three separate experiments. Graphs were created using the SigmaPlot 10.0 software. http://www.jnanobiotechnology.com/content/8/1/15/figure/F5