Atmospheric Plasma Sources as Potential Tools for Surface and Hand Disinfection

Round 1

Reviewer 1 Report

Comments for author File: Comments.docx

Author Response

Response to Reviewer 1 comments:

The authors would like to thank reviewer 1 for his constructive and valuable comments as well as taking the time to review this manuscript. We have carefully considered all comments and hope to have replied to them adequately. Please find the detailed responses below in red and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments:

The result of the study can be summarized as follows: With the CAP plasma jet at 50 W lg reduction of 0.34 on silicone and 0.45 on stainless steel was reached. At 90 W, these values rise to 0.88 lg and 1.12 lg.

Citicism: The title of the publication is misleading because neither disinfection nor germ count reduction of a soap wash (2 lg) is achieved with the jet. Therefore, the title must be changed.

The title has been changed to reflect that CAP may have the potential as a tool in this field

Significance of the study: On hands, an air hand dryer reduced the number of faecal coliforms by 0.4 lg.  Since the investigation with the CAP jet in this study was only carried out on inanimate surfaces, it is questionable whether an analogous efficacy is achieved on the skin and whether the effect of hand drying is surpassed. This must be listed as a limitation.

The following statements are not correct:

• “Hand hygiene, a very simple action, has been well documented to be one of the primary modes of 39 measures for enhancing public safety..”

Only hand antisepsis has been shown to have an impact on reducing the infection rate in the community, but not hand washing [8]. The statement must be changed.

The authors thank the reviewer for their valuable comment. In the statement we gave, we have referred to a study published by Nicolaides et al (2019) that started the following: “From those actions, hand washing is simple and therefore is regularly mentioned as the first recommendation during disease spreading (World Health Organisation, 2009). A scientific study on the effects of hand washing on the bacterial contamination of hands showed that, after a deliberate contamination of individuals by touching door handles and railings in public places, bacteria were found in 44% of the sample. This percentage was reduced to 23% after hand washing with water alone, and to 8% after hand washing with water and plain soap (Burton et al., 2011). The same study showed that the effect of hand washing does not depend on the bacteria species.”

• „Using only electricity and air CAP could, with further optimization, replace or complement current hand disinfection methods...“ The efficacy does not come close to the effectiveness of hand antisepsis, not even that of hand washing. The statement must be corrected.

The statement has been changed to “Using only electricity and air CAP could, with further optimization to increase its efficacy, replace or complement current hand disinfection methods, and mitigate the economic burden of public health crises in the future.”

Only the statement, that the technology can integrated into a hand dryer, is true.

• “Research has shown that CAP can be safely applied to the skin if the energy is well controlled.”

This statement is limited to acute skin tolerance, not to the risks associated with years of use on hands.

Reasons: Depending on the exposure or treatment intensity, which are influenced by the plasma medical device, treatment and target parameters, plasma can have cell inhibitory effects or induce sub-lethal cellular damage, a principle similar to the concepts of ‘oxidative eustress’ promoting physiological and ‘oxidative distress’ causing pathophysiological signaling proposed in redox biology [1]. The question whether plasma exposure is safe, particularly with regards to cell toxic, immunogenic or sensitizing side effects or genotoxicity and therefore carcinogenic potential, has been key for applications on skin. The special problem in the evaluation of safety of CAP is the presence of different radicals in the plasma, whose interaction can lead to different risks than the effect of the single components. I.e. ozone alone and in conjunction with 4-(N-ethyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone or with dibutyl phthalate induce oviductal carcinomas in B6C3F1 mice [2].

Findings on mutagenicity [3-5] and transient expression of pre-mutagenic active compounds, even though the latter was as result of directly exposing DNA [6], suggest that the current risk assessment for plasma applications is still incomplete and there is a need to consider also energy, penetration depth, and the body’s detoxification capacity must also be considered.

Peroxynitrite (ONOO-) induces oxidative and nitrosative DNA damage [3]. Therefore, the dose-dependent risk of a possible carcinogenic risks must be excluded. This applies in particular to the multi-component mixture in CAP. The ability of plasma reactive species to induce damage in DNA molecules has been shown in a number of studies using different types of plasma devices, treatment parameters and gas types [7].

Therefore, it must be clearly stated in the publication that use for hand hygiene is only possible if the risk of carcinogenesis and mutagenesis has been excluded by long-term studies.

This limitation has now been added in the paper: “However, long-term studies still need to be performed to conclusively exclude the risk of carcinogenesis and mutagenesis of CAP [12].”

1. Sies H. On the history of oxidative stress: Concept and some aspects of current development. Curr Opin Toxicol 2018; 7: 122–6.
2. Kim MY, Myc HO. Toxicity and carcinogenicity of ozone in combination with 4-(n-methyl-n-nitrosamino)-1-(3-pyridyl)-1-butanone and dibutyl phthalate in B6C3F1 mice for 16 and 32 weeks. Biomed Environm Sci, 2009, 22(3): 216-22.
3. Kalghatgi SU, Fridman G, Cooper M, Nagaraj G, Peddinghaus M, Balasubramanian M, et al. Mechanism of blood coagulation by non-thermal atmospheric pressure dielectric barrier discharge plasma. IEEE Transact Plasma Sci 2007; 35:1559–66.
4. Ptasinska S, Bahnev B, Stypczynska A, Bowden M, Mason NJ, Braithwaite NSJ. DNA strand scission induced by a non-thermal atmospheric pressure plasma jet. Phys Chem Chem Phys 2010; 12: 7779–81.
5. Garcia-Alcantara E, López-CallejasR, Serment-Guerrero J, Peña-Eguiluz R, MuñozCastro AE, Rodríguez-Méndez BG, et al. Toxicity and genotoxicity in HELA and E. coli cells caused by a helium plasma needle. Appl Phys Res 2013; 5: 21–8.
6. Morales-Ramírez P, Cruz-Vallejo V, Peña-Eguiluz R, López-Callejas R, Rodríguez Méndez B G, Valencia-Alvarado R, et al. Assessing cellular DNA damage from a helium plasma needle. Radiat Res 2013; 179: 669–73.
7. Kim MY, Dong M, Dedon PC, Wogan GN. Effects of peroxynitrite dose and dose rate on DNA damage and mutation in the supF shuttle vector. Chem Res Toxicol 2005;18(1):76-86.
8. Kampf G, Kramer A. Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs. Clin Microbiol Rev. 2004 Oct;17(4):863-93,

Author Response File: Author Response.docx

Reviewer 2 Report

This research presents surface and hand desifenction using atmospheric plasma sources. Paper is very well written with easy to read. There are no major complaints on paper.

Some minor remarks are related to Figure 2 where some parts of the figure needs to be translated to English.

Also in Conclusions part it would be interesitng to put some sentence on economic aspects of this type of desinfection, like cost price, profitability...

Minor editing of English language required.

Author Response

Response to Reviewer 2 comments:

The authors would like to thank reviewer 2 for his constructive and valuable comments as well as taking the time to review this manuscript. We have carefully considered all comments and hope to have replied to them adequately. Please find the detailed responses below in red and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments:

This research presents surface and hand desifenction using atmospheric plasma sources. Paper is very well written with easy to read. There are no major complaints on paper.

Some minor remarks are related to Figure 2 where some parts of the figure needs to be translated to English.

The French parts of the figure have been erased as the explanation is given in the figure legend.

Also in Conclusions part it would be interesitng to put some sentence on economic aspects of this type of desinfection, like cost price, profitability...

We thank the reviewer for this interesting comment. However, we unfortunately did not calculate and costs or economic aspects in this study.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Authors,

Your article entitled " Surface and hand disinfection using Atmospheric Plasma Sources" brings a useful contribution to the research in the field of surface disinfection, so much brought into discussion during the COVID-19 pandemic, from a medical, economical and social point of view.

In my opinion, the paper needs some improvements for the purpose of publication. Please find below my observations:

In the Abstract section:

-the abbreviations should be explained the first time they appear in text (RF, DC).

In the Introduction section:

-line 55 - please remove the comma between "Alternative" and "technologies", as it changes the meaning of the phrase.

In the Materials and methods section:

-line 93 - please mention the name of the author; the same for line 96;

-subsection 2.4, line 133 - please complete the phrase "After disks were ...";

-please specify the value of the statistical cut-off point "p".

In the Results section:

-subsection 3.2.1, line 189 - please consider "the influence of drying" instead of "dying";

-Table 1 - please pay attention to the numerical expression in English (for example, 5.65 instead of 5,65 etc).

In the Discussion section:

-please check the expression "the lipic bilayer of cells" - line 257;

-please add study limitations in the end of this section.

In the Conclusion section: 

-please add a clearer expression of the study main results.

The article needs moderate editing of English language.

Author Response

Response to Reviewer 3 comments:

The authors would like to thank reviewer 3 for his constructive and valuable comments as well as taking the time to review this manuscript. We have carefully considered all comments and hope to have replied to them adequately. Please find the detailed responses below in red and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments:

Your article entitled " Surface and hand disinfection using Atmospheric Plasma Sources" brings a useful contribution to the research in the field of surface disinfection, so much brought into discussion during the COVID-19 pandemic, from a medical, economical and social point of view.

In my opinion, the paper needs some improvements for the purpose of publication. Please find below my observations:

In the Abstract section:

-the abbreviations should be explained the first time they appear in text (RF, DC).

Abbrevieations are now explained the first time they appear

In the Introduction section:

-line 55 - please remove the comma between "Alternative" and "technologies", as it changes the meaning of the phrase.

Comma was removed

In the Materials and methods section:

-line 93 - please mention the name of the author; the same for line 96;

Names were added before the reference number for those lines

-subsection 2.4, line 133 - please complete the phrase "After disks were ...";

Phrase was changed to “Afterwards, disks were were exposed…”

-please specify the value of the statistical cut-off point "p".

In line 203, the phrase “Using a cutoff (α) for statistical significance of 0.05,I it was…” has been added to indicate the cutoff point for p.

In the Results section:

-subsection 3.2.1, line 189 - please consider "the influence of drying" instead of "dying";

Done

-Table 1 - please pay attention to the numerical expression in English (for example, 5.65 instead of 5,65 etc).

The numerical expressions were changes in the figure.

In the Discussion section:

-please check the expression "the lipic bilayer of cells" - line 257;

This has been changed to “lipid bilayer”

-please add study limitations in the end of this section.

In the Conclusion section: 

-please add a clearer expression of the study main results.

The results and limitations of the technology presented here have been outlined more clearly.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

no comments