Technological watch

Viral outbreaks impact global health and healthcare systems; researchers and healthcare professionals advocate using antiviral agents to decrease the spread of viral pathogens. Research published in the journal Emergent Materials has explored the antiviral properties of intermetallic nanoparticles incorporated into polymeric fibers.



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Viruses are the most abundant life form, spreading easily between individuals through direct or indirect contact to cause infectious disease. Their core genetic material is composed of RNA or DNA, surrounded by a proactive protein coat.

There are numerous vaccines designed against viruses, with some leading to the eradication of viral infections like measles and smallpox. However, there are still many pathogens with no available treatment. 

Scientists and pharmaceuticals turn to antiviral agents, which reduce the spread and likelihood of the viruses’ causing infections.

Nanomaterials have the potential to be used in infection treatment as they possess antimicrobial properties.

Intermetallic materials, a kind of metallic alloy composed of two or more elemental metals, exhibit strong antimicrobial properties, particularly copper-based alloys.

This research analyzed the antiviral properties of copper-zinc and copper-silver alloy composites for the first time, as both zinc and silver demonstrated promising antimicrobial activity. Previous work has often concentrated on analyzing the antiviral properties of single elemental nanoparticles.

Experiments were performed in bacteriophages, viruses that infect bacterial cells, as they are showcase structural features similar to animal and human viruses.

MethodologyThe researchers obtained intermetallic copper-silver and copper-zinc nanoparticles. Morphologies were examined with scanning electron microscopy (SEM), and images were processed with built-in software.

A full list of available Scanning Electron Microscopes are listed here.Fourier-transform infrared (FTIR) spectra of the nanoparticles were obtained with a PerkinElmer Frontier FT-IR/FIR spectrometer, and Raman spectra were acquired by a Renishaw inVia Raman microscope. The samples were prepared for elemental and metal trace analysis.

The study used Escherichia coli bacteriophage T4 (to model DNA viruses) and Escherichia coli bacteriophage MS2 (to model RNA viruses) as the model organisms. The viruses were cultured and antiviral activity was determined.

Nanocomposite fibers were developed from poly(methyl methacrylate) (PMMA) employing pressurized gyration. Copper-silver and copper-zinc nanoparticles were introduced into the fibers, and antiviral properties of the fibers were analyzed against bacteriophage T4.

ResultsSEM analysis revealed the morphology of the two intermetallic nanoparticles.

Intermetallic copper-silver and copper-zinc nanoparticles are shown in Figure 1 to be spherical shaped and are agglomerated. The average size of copper-silver was found to be 90–95 nm and copper-zinc was 100–120 nm.



Figure 1. Scanning electron micrographs of (a) copper-silver and (b) copper-zinc nanoparticles. Image Credit: Matharu, et al., 2021. Image Credit: Matharu, R. K., et al (2021)

Figure 2 displays both FTIR (red) and Raman (blue) spectra of the intermetallic nanoparticles.



Figure 2. FTIR and Raman spectra of (a) copper-silver and (b) copper-zinc nanoparticles. Image Credit: Matharu, et al., 2021

Detectable amounts of metal ions and concentrations of major ions (silver, copper, and zinc) evaluated from wholly digested copper silver and copper-zinc samples are displayed in Table 1.

Table 1. ICP-OES metal trace and elemental analysis of intermetallic copper-silver (CuAg) and copper-zinc (CuZn). Source: Matharu, et al., 2021

ICP digested sample CuAg CuZn Traced ion Ca, Mn, Zn, Br Fe, Ni, W, Br Main ion Cu Ag Cu Zn Mean (ppm) 0.08035 5.752 4.1860 2.2561 wt% 1.38 98.62 65.0 35.0 Mole ratio 0.022 0.914 1.023 0.535 Calculated formula Cu0.60Ag25 Cu21Zn11 Standardised formula CuAg42 Cu2Zn The viricidal properties of copper-zinc and copper-silver nanoparticles were evaluated against bacteriophages T4 and MS2. The number of infectious viral particles was quantified by a plaque assay before and after treatment.

Figure 3 depicts the antiviral activity of all concentrations analyzed. Researchers found that the nanoparticles were highly effective against bacteriophage MS2 rather than bacteriophage T4.



Figure 3. Antiviral activity of copper-silver and copper-zinc intermetallic nanoparticles at 0.05, 0.1, 0.25, 0.5, 1.0, and 2.0 w/v% against (a) bacteriophage MS2 for 3 and 24 hours and (b) bacteriophage T4 for 3 and 24 hours. Error bars represent standard deviation. 0.0 w/v% is the negative control. Image Credit: Matharu, et al., 2021

Copper-silver intermetallic nanoparticles, in particular, were highly potent against bacteriophage T4 than copper-zinc nanoparticles.

Figure 4 displays the antiviral properties of nanocomposite polymeric fibers when evaluated against T4 bacteriophage.



Figure 4. Antiviral activity of intermetallic nanocomposite fibers after 3 hours incubation. Error bars represent standard deviation. Negative control represents pure PMMA fibers. Image Credit: Matharu, et al., 2021

DiscussionNanoparticles used in these investigations were characterized by various techniques. For instance, SEM analysis exposed that copper-zinc intermetallic nanoparticles were somewhat bigger than copper-silver nanoparticles, while FTIR analysis revealed that copper-zinc and copper-silver were free from organic contaminants.

Antiviral activity tests revealed that the nanoparticles were more efficient against RNA viruses when compared to DNA viruses; however, this analysis needs further evaluation.

The presence of zinc or silver in the compounds is attributed to a difference in potency. The viricidal activity of the intermetallic nanoparticles depends on the nanoparticles’ interaction with viral envelope glycoproteins, which inhibits viral diffusion and penetration into the host cell.

Intermetallic copper-silver nanoparticles exhibit greater antiviral properties when compared to single elemental nanoparticles, supported by previous and current research. Copper-zinc intermetallic nanoparticles showed synergistic antiviral properties of all three concentrations analyzed.

Antiviral agents and carrier polymeric matrices enhance the usability of the material enabling its use in commercial, industrial, and consumer applications. For this reason, copper-zinc and copper-silver intermetallic nanoparticles were introduced into polymeric fibers to evaluate their efficacy against viruses.

It was noticed that pure polymer (PMMA) fibers exhibited a moderate decrease in virions. Fibers with copper-silver nanoparticles showed slightly greater antiviral properties compared to fibers having copper-zinc intermetallic nanoparticles. The toxicity of intermetallic nanoparticles against viruses is evident, but its effect on human cells needs further investigation.

ConclusionThe current study details the antiviral properties of intermetallic copper-zinc and copper-silver nanoparticles. Antiviral analyses showed that both nanoparticles are effective against RNA viruses, while copper-silver nanoparticles were much potent against DNA viruses.

Also, their ability to be effective when introduced into polymeric fibers shows the potential of these nanoparticles in numerous applications, from environmental to biomedical engineering.

Continue reading: NANO-LLPO: Using Nanomaterials to Heal Wounds.

Journal Reference:Matharu, R. K., Cheong, Y.-K., Ren, G., Edirisinghe, M., Ciric, L. (2021) Exploiting the antiviral potential of intermetallic nanoparticles. Emergent Materials. Available at: https://doi.org/10.1007/s42247-021-00306-2

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Megan CraigMegan graduated from The University of Manchester with a B.Sc. in Genetics, and decided to pursue an M.Sc. in Science and Health Communication due to her passion for combining science with content creation. As part of her studies, Megan partnered with Jodrell Bank Discovery Centre as a Digital Marketing Assistant, producing content and updating sections of their website. In her spare time, she loves to travel, exploring each location's culture and history - including the local cuisine. Her other interests include embroidery, reading fiction, and practicing her Japanese language skills.

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