SiO2-Ag Composite as a Highly Virucidal Material: A Roadmap that Rapidly Eliminates SARS-CoV-2

Abstract

COVID-19, as the cause of a global pandemic, has resulted in lockdowns all over the world since early 2020. Both theoretical and experimental efforts are being made to find an effective treatment to suppress the virus, constituting the forefront of current global safety concerns and a significant burden on global economies. The development of innovative materials able to prevent the transmission, spread, and entry of COVID-19 pathogens into the human body is currently in the spotlight. The synthesis of these materials is, therefore, gaining momentum, as methods providing nontoxic and environmentally friendly procedures are in high demand. Here, a highly virucidal material constructed from SiO2-Ag composite immobilized in a polymeric matrix (ethyl vinyl acetate) is presented. The experimental results indicated that the as-fabricated samples exhibited high antibacterial activity towards Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as well as towards SARS-CoV-2. Based on the present results and radical scavenger experiments, we propose a possible mechanism to explain the enhancement of the biocidal activity. In the presence of O2 and H2O, the plasmon-assisted surface mechanism is the major reaction channel generating reactive oxygen species (ROS). We believe that the present strategy based on the plasmonic effect would be a significant contribution to the design and preparation of efficient biocidal materials. This fundamental research is a precedent for the design and application of adequate technology to the next-generation of antiviral surfaces to combat SARS-CoV-2.

PVC-SiO2-Ag composite as a powerful biocide and anti-SARS-CoV-2 material

“…This is mainly due to the following factors: (i) the SPR adsorption and high electron trapping ability of Ag NPs are beneficial for promoting solar energy conversion [ 19 , 20 ], water splitting [ 21 , 22 ], photocatalytic [ 23 – 25 ] and antimicrobial [ 26 – 29 ] activities of the composites, (ii) the excellent conductivity of Ag NPs at the interface improve the transfer of charges from SPR metals to semiconductors, thus leading to enhanced activity[ 30 ]. Previously, we demonstrated an anti-SARS-CoV-2 activity, which efficiently hampered infection and transmission via surfaces; in particular, an antimicrobial coating, a polycotton fiber Ag based material, that could rapidly kill bacteria Staphylococcus aureus ( S. aureus ), Escherichia coli ( E. coli ), fungi ( Candida albicans ), and SARS-CoV-2 by contact was presented [ 31 ].…”

“…Taking advantage of SiO 2 as an efficient host for stabilizing Ag NPs and the SiO 2 -Ag heterojunction has attracted considerable attention due to its excellent properties [ 36 – 38 ], in the following study by our research group, Ag NPs were stabilized with semiconductor amorphous SiO 2 to form a SiO 2 -Ag heterojunction. This heterojunction was immobilized in a polymeric matrix (ethyl vinyl acetate), to render a highly virucide material [ 31 ]. In this study, we also confirmed, by using scavenger experiments, that hole (h + ), hydroxyl radical (⦁OH), and hydroperoxyl radical (⦁O 2 H) are the reactive species along the mechanism of the virus elimination process [ 31 ].…”

“…This heterojunction was immobilized in a polymeric matrix (ethyl vinyl acetate), to render a highly virucide material [ 31 ]. In this study, we also confirmed, by using scavenger experiments, that hole (h + ), hydroxyl radical (⦁OH), and hydroperoxyl radical (⦁O 2 H) are the reactive species along the mechanism of the virus elimination process [ 31 ]. It is assumed that the formation and separation of electrons, e − , and h + , are enhanced due to the synergistic interaction/effect generated at the surface of the SiO 2 semiconductor and the SPR of the Ag NPs at the interface.…”

“…In the semiconductor, the h + , at the valence band, reacts with H 2 O by decomposing it into ⦁OH and a proton (H + ). The e − migrates to the conduction band reacting with O 2 to form a superoxide radical (⦁O 2 − ), which in turn interacts with H + forming the radical ⦁O 2 H. These free radicals are capable of killing microorganisms by oxidizing and breaking down the cell walls and membranes of bacteria, fungi, and viruses, as demonstrated in different heterojunctions formed by Ag NPS and binary and ternary metal oxides [ 31 ].…”

“…The experimental results indicated that the as-fabricated samples exhibited high antibacterial activity towards E. coli and S. aureus as well as towards SARS-CoV-2 [ 31 ]. Furthermore, this activity can be functionalized as a new technology in the manufacture of medical devices, such as reusable masks and pharmaceutical packaging, food storage packaging materials, displaying high flexibility, biostability and easy processing [ 39 – 41 ].…”