Efficient inactivation of the contamination with pathogenic microorganisms by a combination of water spray and plasma-activated air

Abstract

The global pandemic caused by SARS-CoV-2 has lasted two and a half years and the infections caused by the viral contamination are still occurring. Developing efficient disinfection technology is crucial for the current epidemic or infectious diseases caused by other pathogenic microorganisms. Gas plasma can efficiently inactivate different microorganisms, therefore, in this study, a combination of water spray and plasma-activated air was established for the disinfection of pathogenic microorganisms. The combined treatment efficiently inactivated the Omicron-pseudovirus through caused the nitration modification of the spike proteins and also the pathogenic bacteria. The combined treatment was improved with a funnel-shaped nozzle to form a temporary relatively sealed environment for the treatment of the contaminated area. The improved device could efficiently inactivate the Omicron-pseudovirus and bacteria on the surface of different materials including quartz, metal, leather, plastic, and cardboard and the particle size of the water spray did not affect the inactivation effects. This study supplied a disinfection strategy based on plasma-activated air for the inactivation of contaminated pathogenic microorganisms.

Keywords: Bactericidal effects; Nitration modification; Plasma-activated air (PAA); Reactive species; SARS-CoV-2 Omicron variant.

Graphical abstract

Fig. 1

Experimental setup of the combined treatment of water spray and PAA. A. Scheme diagram of the experimental system. The ambient air was used as working gas to generate plasma and the plasma was flown with airflow to form PAA. For the combined treatment, the water spray and the PAA were introduced into the treatment chamber, respectively, and the samples were first treated with water spray and then with PAA. B. Photo of the experimental system. C. Gaseous components in the PAA detected by the FTIR.

Fig. 2

Prevention of the infection of Omicron-pseudovirus by the combined treatment. A. Inactivation effects on Omicron-pseudovirus by the water spray and 3-min or 6-min PAA treatment. B. Inactivation effects on the Omicron-pseudovirus at different distances to the outlet of the water spray and PAA. The Omicron-pseudovirus was treated with the combination of water spray and 3-min or 6-min PAA treatment, and untreated pseudovirus infected the HEK-293 T cells overexpressing human ACE2. After culturing for 48 h, the RLU values of the cells infected with pseudovirus were measured. C. Transmission electron microscopy (TEM) analysis of the Omicron-pseudovirus treated with the combined treatment. The Omicron-pseudovirus was treated with the combination of water spray and 3-min or 6-min PAA treatment, and untreated pseudovirus was negative-stained and examined by using TEM. The bars represent 200 nm.

Fig. 3

Inactivation of the Omicron-RBD by the combined treatment. A. Inactivation effects on the Omicron-RBD by the water spray and 3-min or 6-min PAA treatment. B. Inactivation effects on the Omicron-RBD at different distances to the outlet of the water spray and PAA. The binding curves of the untreated and treated Omicron-RBD to the immobilized hACE2 were analyzed by ELISA. C. Mass spectrum of the untreated peptide and the peptide treated with the combined treatment. The synthesized peptide PTYGVGHQ from the Omicron-RBD treated with the combined treatment and untreated were analyzed by LC-MS.

Fig. 4

Reactive species generated in the water spray after the PAA treatment. A. Long-lived species of H₂O₂, NO₂⁻, and NO₃⁻. B. Short-lived species determined by the fluorescent probes of TPT and tMVP, and the spin-adduct TEMPONE. The water spray after the PAA treatment for 6 min was recovered to measure the reactive species in the PAA-activated spray. The fluorescent probes TPT and tMVP were mixed with the recovered PAA-activated spray and incubated at room temperature for 10 min, then the fluorescence intensities were measured. The spin trap TEMPONE-H was mixed with the recovered PAA-activated spray and the concentrations of the spin-adduct TEMPONE were measured.

Fig. 5

Bactericidal effect of the combined treatment. A. Bactericidal effect on the bacteria by the water spray and 3-min or 6-min PAA treatment. B. Bactericidal effects on the bacteria at different distances to the outlet of the water spray and PAA. The dried P. aeruginosa or MRSA samples were treated with water spray for 1 min and with PAA for 3 min or 6 min. After treatment, the bacteria were resuspended in PBS buffer and the numbers of survival bacteria were determined by serial dilution, plating, and counting of the resulting CFU. The asterisks represent the numbers of survival bacteria lower than the limit of detection.

Fig. 6

The scheme of the improved combined treatment system. The treatment chamber was replaced by a funnel-shaped nozzle to form a temporary sealed space.

Fig. 7

Inactivation effects of the combined treatment on microorganisms on the surface of different materials. A. Omicron-pseudovirus. B. P. aeruginosa. C. MRSA. The asterisks represent the numbers of survival bacteria lower than the limit of detection.

Fig. 8

Inactivation effects of the combined treatment with the spray of different sizes. A. Photos and sizes of the spray particles prepared by the metal nozzle, medical nebulizer, and commercialized atomizer. B and C. Inactivation effects of the combined treatment with the spray prepared by the metal nozzle, medical nebulizer, and commercialized electric atomizer on the Omicron-pseudovirus (B), the bacteria of P. aeruginosa and MRSA (C). The asterisks represent the numbers of survival bacteria lower than the limit of detection.