A recent study posted to the bioRxiv* preprint server indicated that combining a hydrogen peroxide (H2O2)-based disinfectant and cellulosic copper (Cu) nanoparticles lowered human coronaviruses’ (HuCoVs) infectivity.
Background
The viral respiratory infection, severe acute respiratory syndrome (SARS), is caused by HuCoVs such as the Middle East respiratory syndrome CoV (MERS-CoV), SARS-CoV, and SARS-CoV-2. Although their principal mechanism of transmission is via contaminated respiratory droplets from virus-infected carriers, the viral transmission may also be aided by the deposition of expelled virus particles on fomites and surfaces.
Prior reports demonstrated that the disinfection of high-touch non-porous surfaces lowers the chances of SARS-CoV-2 transmission through fomites. Viruses and bacteria are effectively inactivated by Cu alloys comprising at least 70% Cu and Cu-based surfaces.
The release of redox-active Cu ions from the Cu-based surfaces is responsible for their antimicrobial activities. The lipid bilayer membrane of viruses and bacteria is severely damaged by continuous Cu release. Increased inflow of Cu ions into the viral particle or cell due to the breakdown of membrane integrity promotes oxidative damage to nucleic acids, proteins, and lipids. Microbe-Cu interactions are essential for Cu-based surface-facilitated microbial killing, even though the pathways leading to microbial cell death differ depending on the kind of microorganism.
About the study
In the present study, the researchers analyzed spike (S)-facilitated HCoVs entry into the substrate cells using pseudo viral particles of replication-deficient murine leukemia virus (MLV) expressing MERS-CoV, SARS-CoV-2, and SARS-CoV S proteins on their surface.
Carboxymethyl cellulose (CMC) nanofibers coupled with copper (Cu) possess potent antimicrobial characteristics. The team employed the nanostructure of CMC as a physical template to stabilize and generate nanoparticles containing Cu. The researchers estimated these Cu-containing nanoparticles’ employability as an antimicrobial nanocomposite towards enveloped MLV-based pseudovirions harboring the three aforesaid HCoVs S proteins.
The cellulosic Cu nanoparticles’ effect on S protein-mediated entry of pseudovirion was estimated using a 15-minute or 30-second treatment of CMC-Cu on the MLV-based pseudovirions. In line with the American Society for Testing and Materials (ASTM) International standard (E-1052), a 30-second CMC-Cu treatment was performed, addressing the hand hygiene techniques against enveloped viruses like SARS-CoV-2. The second 15-minute CMC-Cu treatment was used to see if the virucidal impact was comparable to the 30-second treatment.
To compare the potency of CMC-Cu in inactivating S-expressing pseudovirions, the researchers utilized SaberTM, an H2O2-based disinfectant, at dilutions of 1:100 and 1:250. SaberTM contains sodium dodecylbenzenesulfonate, an anionic surfactant, additional to H2O2 to boost its virucidal activity. Further, the antimicrobial activity of CMC-Cu coupled with SaberTM was also estimated in the study.
Results and discussions
The results indicated that a 30-second treatment of CMC-Cu substantially inactivated the MERS-CoV-, SARS-CoV-2-, and SARS-CoV-S pseudotyped particles. The luciferase activity of S-pseudovirions was reduced from 86% to 98% when treated with 1:100 dilution of CMC-Cu. Further, the infectivity of S-pseudovirions was virtually eliminated when treated with the 1:25 dilution of CMC-Cu. These data equate to a clear decrease in viral infectivity in the context of SARS-CoV-2-S pseudovirions, with a 1.6 log10, 2.4 log10, and 3.2 log10 drops at 1:100, 1:50, and 1:25 dilutions, respectively.
Moreover, a 30-second CMC-Cu treatment was as efficacious as a 15-minute exposure for pseudoviral particle inactivation. According to the current findings, the benefit of employing CMC-Cu was that it offers a quick virucidal impact on S-pseudoviral particles, prompting inactivation after just 30-seconds.
MERS-CoV-, SARS-CoV-2-, and SARS-CoV-S were susceptible to 30-second exposure to SaberTM. Following treatment with 0.4% SaberTM, the infectivity of S-pseudoviral particles reduced from 99.4% to 98.7%. SARS-CoV-2-S pseudovirions treated with 0.4% and 1% SaberTM for 30-seconds demonstrated 2.2- and 2.5-log10 or more inactivation, respectively. These reductions in reporter activity indicate that the S-pseudoviral particles infectivity was abolished by treatment with 1% and 0.4% SaberTM for 30 seconds.
The S-pseudovirions were more susceptible to SaberTM-CMC-Cu cocktail than CMC-Cu or SaberTM alone. SaberTM-CMC-Cu treatment resulted in a 2.8-log10 drop in SARS-CoV-2 S-pseudotyped particles, which was a 100% decrease relative to background concentrations of infectivity reported with Δenv pseudoviral particles in Vero E6 cell experiments.
Further, a comparable Cu1+-dependent reactive oxygen species (ROS)-catalyzed nanoparticles-induced microbial death since the hydroxyl radical quencher Tiron and Cu1+ chelator tetrathiomolybdate (TTM) shielded S-pseudovirions from CMC-Cu action.
Conclusions
The study findings demonstrated that when S-pseudovirions were treated with CMC-Cu nanoparticles for 30 seconds, their capacity to infect target Vero E6 cells was dramatically reduced, resulting in nearly 97% lower infectivity than untreated pseudovirions. On the contrary, treatment with the Cu chelator TTM protected S-pseudovirions against CMC-Cu-facilitated deactivation.
The infectivity of S-pseudovirions was drastically decreased by around 98% when they were exposed to an H2O2-based disinfectant called SaberTM at 1:16 dilution. Nonetheless, in Vero E6 cell experiments, combining CMC-Cu and SaberTM was the most efficient way to limit infectivity of MERS-CoV, SARS-CoV-2, and SARS-CoV-S pseudovirions.
The present study revealed that cellulosic Cu nanoparticles boost the efficiency of diluted SaberTM sanitizer, paving the way for a more effective method to reduce the likelihood of enveloped respiratory virus transmission through fomites and surfaces.
*Important notice
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
