Cationic Surfactants as Disinfectants against SARS-CoV-2

Abstract

The virucidal activity of a series of cationic surfactants differing in the length and number of hydrophobic tails (at the same hydrophilic head) and the structure of the hydrophilic head (at the same length of the hydrophobic n-alkyl tail) was compared. It was shown that an increase in the length and number of hydrophobic tails, as well as the presence of a benzene ring in the surfactant molecule, enhance the virucidal activity of the surfactant against SARS-CoV-2. This may be due to the more pronounced ability of such surfactants to penetrate and destroy the phospholipid membrane of the virus. Among the cationic surfactants studied, didodecyldimethylammonium bromide was shown to be the most efficient as a disinfectant, its 50% effective concentration (EC50) being equal to 0.016 mM. Two surfactants (didodecyldimethylammonium bromide and benzalkonium chloride) can deactivate SARS-CoV-2 in as little as 5 s.

Keywords: COVID-19; SARS-CoV-2; cationic surfactants; disinfectants; quaternary ammonium compounds; virucidal activity.

Figure 1

Molecular structure of cationic surfactants under study.

Figure 2

Effects of hydrophobicity on the virucidal activity of cationic surfactants against SARS-CoV-2: (left) effect of the length of the hydrophobic tail (for C8Py, C12Py, and C16Py surfactants having the same hydrophilic pyridinium head group) and (right) effect of the number of hydrophobic tails (for C12DMA and C12-C12DMA surfactants) on the values of the inhibition coefficient, observed at 0.28 mM concentration of each surfactant.

Figure 3

Inhibition coefficient as a function of: (a) critical micelle concentration cmc and (b) hydrophile-lipophile balance HLB of different cationic surfactants for SARS-CoV-2 inactivation by 0.28 mM surfactant solutions (contact time 1 h).

Figure 4

50% effective concentrations EC50 for SARS-CoV-2 inactivation as a function of critical micelle concentration cmc of different cationic surfactants in semi-logarithmic representation.

Figure 5

Kinetics of SARS-CoV-2 inactivation by 0.14 mM benzalkonium chloride at different virus-disinfectant contact times.

Figure 6

Micrographs displaying the time course of the development of SARS-CoV-2-induced cytopathic effects CPE in the Vero E6 cell monolayer. The CPE were visually scored for each well in a blinded fashion by two independent observers. Wells with 0, 25, 50, 75, and 100% cells exhibiting CPE or viability loss were scored, respectively, CPE–, CPE+, CPE++, CPE+++, and CPE++++. The photo in Panel (A) shows non-infected cells (no-virus control) after 72 h of incubation (no CPE or dead cells). Panels (B) and (C) show, respectively, cells inoculated with 10³ TCID₅₀/mL 36 and 72 h post-infection. About 50% of cells in Panel B exhibit CPE or loss of viability (score: CPE++). In Panel (C), all cells are dead (score: CPE++++). The photos were taken using an inverted microscope (×200 magnification; Leitz Diavert, Wetzlar, Germany).

Figure 7

Polarity parameter of pyrene I₁/I₃ as a function of the concentration of cationic surfactants: benzalkonium chloride BAC and benzyldimethyldodecylammonium chloride C12BAC.