People who come in contact with coronavirus disease 2019 (COVID-19) patients are high-risk individuals for becoming infected with its causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Viral transmission in hospitals is a particular area of concern, as the close interaction between the healthcare personnel and the patients helps the transmission of the virus – between them, their families and subsequently to their communities.

Despite various public health interventions implemented, such as adaptation of areas with negative air pressure, isolation areas for patients with COVID-19, and the mandatory use of personal protective equipment (PPE), controlling SARS-CoV-2's spread has had mixed results. In the absence of effective antiviral treatments, the ongoing vaccination campaign is the main strategy across the globe to prevent SARS-CoV-2.

In a recent study by a team of researchers in Mexico, Russia and Spain, silver nanoparticles (AgNPs) were found to inhibit SARS-CoV-2 in healthcare workers. They propose a non-pharmaceutical public health intervention consisting of mouthwash and nose rinse with an AgNPs solution to reduce morbidity among healthcare personnel exposed to the SARS-CoV-2 virus.

Study: Evaluation of silver nanoparticles for the prevention of SARS-CoV-2 infection in health workers: in vitro and in vivo. Image Credit: Pavelis / Shutterstock

The researchers demonstrated clinical evidence to confirm the prevention of SARS-CoV-2 infection in health personnel who performed mouthwash and nose rinse solution with AgNPs.

To our knowledge, this study is the first experimental in vitro and in vivo trial where AgNPs as mouthwash and nasal rinse solution are applied for SARS-CoV-2 contagion prevention," say the researchers.

The study, published on the preprint medRxiv* server, tested a mouthwash ARGOVIT® AgNPs which contains AgNPs and evaluated for prevention of SARS-CoV-2 infection in health workers.

This is an oral and nasal hygiene product registered and made in Russia. It contains metallic silver, polyvinylpyrrolidone, hydrolyzed collagen and distilled water. The hydrolyzed collagen stabilizes the AgNPs and reduces the cytotoxicity. AgNPs have been demonstrated to have robust antimicrobial, including antiviral, effects.

First, they demonstrated the antiviral activity of the AgNPs in Vero E6 cell cultures. The researchers observed a dose-dependent inhibitory effect of AgNPs over SARS-CoV-2 infectivity.

Second, the researchers designed a randomized controlled study of two-group (experimental vs. control) to evaluate the efficacy of the mouthwash and nasal rinse with AgNPs solution for preventing SARS-CoV-2 infection in the health personnel at the General Tijuana Hospital in Mexico. These individuals (n=231) work in high-risk areas with direct contact with patients infected and diagnosed with COVID-19 and/or atypical pneumonia.

This study was carried out for 9 weeks during the declaration of the pandemic in Mexico (beginning on April 7 through June 9, 2020). The researchers confirmed the diagnosis of COVID-19 among the participants by monitoring the symptoms, conducting RT-PCR, randomly selecting for CT chest scans and clinical evaluation.

Using logistic regression, the strong relationship between the fact of mouthwashes and nose rinse in the health personnel and the mitigation of the SARS-CoV-2 contagion with an efficiency of 84.8% is proved."

Significantly, the study also showed no harmful side effects in the participants who used AgNPs as a mouthwash and nasal rinse for 9 weeks. The researchers observed that the incidence of SARS-CoV-2 infection significantly reduced in the "experimental" group (two participants out of 114 were COVID-19 positive, 1.8%) compared to the "control" group (thirty-three participants out of 117 were COVID-19 positive, 28.2%). This calculated to an efficiency of 84.8%, suggesting that the mouthwash could be an effective use of AgNPs in preventing SARS-CoV-2 infection.

The researchers also recommended the application to prevent SARS-CoV-2 infection in high-risk areas such as dental procedures. Because the oropharynx and nasopharynx are the initial entry sites for SARS-CoV-2 and it replicates to produce a viral load of 1.2 × 108 infectious copies/per mL, it is a high risk of exposure for the odontologist.

The evidence presented in this study suggests that the application of mouthwashes and nose rinse can significantly reduce the viral load in these areas, to reduce transmission, in addition to the use of personal protective equipment by healthcare personnel," the researchers said.

This study presents a new non-pharmaceutical intervention using nanoparticles in a clinical setting to reduce the spread, and/or pathogenicity of SARS-CoV-2 associated with COVID-19.

Proving its inhibitory effect on SARS-CoV-2 infectivity in vitro it is inferred that the use of AgNPs as a mouthwash and nose rinse will be very useful as a prophylactic for the prevention of SARS-CoV-2, not only for healthcare personnel but also as additional protection for the general population, the researchers write.

*Important Notice

medRxiv 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.

Written by

Dr. Ramya Dwivedi

Ramya has a Ph.D. in Biotechnology from the National Chemical Laboratories (CSIR-NCL), in Pune. Her work consisted of functionalizing nanoparticles with different molecules of biological interest, studying the reaction system and establishing useful applications.