Antibacterial Activity of Polypropylene Meshes for Hernioplasty with Ag and (Ag,Cu) Coatings Deposited via Magnetron Sputtering

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript addresses an important area in surgical implant technology by investigating antibacterial coatings on hernioplasty meshes. The authors present experimental findings on the effectiveness of Ag and Ag,Cu coatings in enhancing antimicrobial properties. However, the manuscript requires a Major Revision before being considered for publication to enhance the study's rigor and clarity. Below are detailed comments, including critical questions and suggestions for improving the manuscript's scientific quality and presentation:

Major issues: 

1. Were polypropylene meshes without any coating tested as a control group? If not, please include an uncoated control in all tests, as it is essential for distinguishing the net effect of the coatings.

2. How does the chosen magnetron sputtering technique compare to alternative methods, such as electrochemical or sol-gel coatings, regarding efficiency and outcomes? Including a brief comparison would help readers contextualize the technology's novelty and relevance.

3. The literature review is limited in scope regarding the applications of Cu and Ag in biomedical coatings. An expanded review on integrating copper and silver in implant coatings would strengthen the manuscript’s context and relevance. Specifically, recent studies have demonstrated that combining Cu and Ag enhances the antimicrobial and biocompatibility properties of implants, which could inform both the rationale and interpretation of your findings: https://doi.org/10.1016/j.matchemphys.2021.125436; https://doi.org/10.3390/ma13061415.

4. The study uses only Staphylococcus aureus as the test strain. Given the clinical significance of other pathogens (e.g., Escherichia coli, Pseudomonas aeruginosa) in surgical infections, why were these not included? Adding tests with a broader range of clinically relevant bacteria would strengthen the manuscript’s findings.

5. The manuscript mentions a reduction in microbial contamination percentage but lacks statistical analysis to confirm the significance of these reductions. Can you provide statistical analysis to validate the antimicrobial effects of each coating type?

6. The authors should address how these coatings impact bacterial biofilm formation. The discussion on biofilm-resistant properties, especially against biofilm-forming pathogens, could further emphasize the utility of the coatings in preventing implant-related infections.

7. Can you include a hypothesis or supporting literature explaining the mechanisms by which Ag and Cu ions contribute to bacterial inhibition? Adding this would provide clarity on how these coatings prevent bacterial growth.

8. The SEM and TEM images presented could be better explained regarding structural differences between Ag-only and (Ag,Cu) coatings. How does the thickness and grain structure correlate with the observed antibacterial properties?

9. Polypropylene-based meshes in hernioplasty undergo significant mechanical stress. Has the durability of these coatings under simulated physiological conditions been assessed? If not, this is a critical area for future research.

10. The manuscript notes the potential overheating of polypropylene during coating application. How do the temperature cycles affect polypropylene’s mechanical properties and structure? Please clarify whether any weakening of the mesh is expected from the coating process.

Minor Comments and Suggestions:

1. The manuscript contains some grammatical and syntactical errors. A thorough language edit is recommended to improve readability and comprehension.

2. Expand all acronyms upon their first use. For example, the term "CFU" should be defined (Colony-Forming Units) when initially introduced to aid readers less familiar with microbiological terminology.

3. Figures 2 and 3 could benefit from annotations or labels indicating critical features, such as coating layers or specific morphological characteristics. This would improve readers' ability to interpret the structural differences.

4. The manuscript references several studies in the introduction but could benefit from a clearer linkage to recent advancements in antimicrobial coatings for medical implants. Including more current studies (e.g., post-2020) on advances in coating technologies or infection resistance in biomaterials could provide a broader context for your work.

Comments on the Quality of English Language

There are several grammatical errors and awkward phrasing throughout the manuscript. I recommend that the authors have the manuscript professionally proofread or thoroughly revised to ensure readability and clarity.

Author Response

R1: Comments and Suggestions for Authors

R: The manuscript addresses an important area in surgical implant technology by investigating antibacterial coatings on hernioplasty meshes. The authors present experimental findings on the effectiveness of Ag and Ag,Cu coatings in enhancing antimicrobial properties. However, the manuscript requires a Major Revision before being considered for publication to enhance the study's rigor and clarity. Below are detailed comments, including critical questions and suggestions for improving the manuscript's scientific quality and presentation:

A: The authors are grateful to the reviewer for his attention to the manuscript and a number of valuable recommendations to improve its quality.

Major issues: 

R: 1. Were polypropylene meshes without any coating tested as a control group? If not, please include an uncoated control in all tests, as it is essential for distinguishing the net effect of the coatings.

A: Unfortunately, the uncoated mesh sample was not tested, since the object of the study was a commercially available polypropylene mesh manufactured by UNISUR (Karnataka, India) without any antibacterial properties (according to the information provided by the manufacturer). In addition, we were unable to find any information in the literature that polypropylene itself has antibacterial properties. Repeating the experiments and comparing with uncoated samples would require a long time (due to the preparation of coated samples), and creating the same conditions (nutrient medium with the same contamination - the number of bacterial colonies) only for the uncoated mesh is practically impossible. However, we are grateful to the Reviewer and will definitely take this remark into account in further studies.

R: 2. How does the chosen magnetron sputtering technique compare to alternative methods, such as electrochemical or sol-gel coatings, regarding efficiency and outcomes? Including a brief comparison would help readers contextualize the technology's novelty and relevance.

A: The magnetron sputtering method is a fundamentally different coating formation technology. This article shows that this method can also impart antibacterial properties to medical devices. We did not aim to compare the properties of coatings obtained by different methods, but only indicated the achievability of the antibacterial result of coatings obtained by magnetron sputtering. This method of coating deposition allows for high adhesion strength with the substrate and is not yet widely used for depositing antibacterial coatings on a polymer base.

R: 3. The literature review is limited in scope regarding the applications of Cu and Ag in biomedical coatings. An expanded review on integrating copper and silver in implant coatings would strengthen the manuscript’s context and relevance. Specifically, recent studies have demonstrated that combining Cu and Ag enhances the antimicrobial and biocompatibility properties of implants, which could inform both the rationale and interpretation of your findings: https://doi.org/10.1016/j.matchemphys.2021.125436; https://doi.org/10.3390/ma13061415.

A: The authors are grateful to the Reviewer for recommendations, the review part of the article was expanded, a review of studies aimed at describing the effect of Ag/Cu coatings on the properties of meshes was added. The article recommended by the Reviewer was taken into account in the review part.

R: 4. The study uses only Staphylococcus aureus as the test strain. Given the clinical significance of other pathogens (e.g., Escherichia coli, Pseudomonas aeruginosa) in surgical infections, why were these not included? Adding tests with a broader range of clinically relevant bacteria would strengthen the manuscript’s findings.

A: The authors are grateful to the reviewer for recommendations. The aim of this study was to obtain a coating with antibacterial properties on a polypropylene mesh using magnetron sputtering. The antibacterial properties were tested in the laboratory for the prevention and treatment of bacterial infections of the A.V. Vishnevsky National Medical Research Center of Surgery of the Ministry of Health of the Russian Federation (Moscow, Russia). At the same time, the vast majority of scientific articles devoted to studies of the antibacterial properties of medical devices use this particular test strain (Staphylococcus aureus), and this strain is resistant to various types of broad-spectrum antibiotics. Therefore, it was decided to begin the research with this strain. In the future, we plan to expand our research to other strains that cause infection during surgical intervention. The authors added a justification for their choice of strain for the study.

R: 5. The manuscript mentions a reduction in microbial contamination percentage but lacks statistical analysis to confirm the significance of these reductions. Can you provide statistical analysis to validate the antimicrobial effects of each coating type?

A: The authors are grateful to the Reviewer for the recommendation. Unfortunately, this analysis was not carried out, since these were exploratory studies (the samples were in one copy, only the coating compositions varied). In future works, we will conduct more detailed work (on a larger number of samples of the same type) and evaluate the statistical significance of the decrease in antibacterial activity.

 

R: 6. The authors should address how these coatings impact bacterial biofilm formation. The discussion on biofilm-resistant properties, especially against biofilm-forming pathogens, could further emphasize the utility of the coatings in preventing implant-related infections.

A: Undoubtedly, the authors agree with the importance and necessity of these studies, but the purpose of this article was to study the possibility of forming antibacterial coatings on a polypropylene substrate using magnetron sputtering, which was established. How these coatings affect the formation of bacterial biofilm, as well as a discussion of the resistance properties of medical devices to pathogens that form biofilms will be the subject of research in our future works. The authors are grateful to the Reviewer for the recommendation for future studies.

R: 7. Can you include a hypothesis or supporting literature explaining the mechanisms by which Ag and Cu ions contribute to bacterial inhibition? Adding this would provide clarity on how these coatings prevent bacterial growth.

A: Explanations have been added as per the Reviewer's recommendations.

R: 8. The SEM and TEM images presented could be better explained regarding structural differences between Ag-only and (Ag,Cu) coatings. How does the thickness and grain structure correlate with the observed antibacterial properties?

A: Unfortunately, we did not conduct a study on the correlation of the thickness and granularity of the coating structure with the observed antibacterial properties within the framework of this work. The coatings were of the same type in morphology and architecture. But we will take this remark into account in further studies.

R: 9. Polypropylene-based meshes in hernioplasty undergo significant mechanical stress. Has the durability of these coatings under simulated physiological conditions been assessed? If not, this is a critical area for future research.

A: Thank you for the recommendations. Yes, in this work we did not evaluate the durability of coated meshes in simulated physiological environments. We plan to devote further research to this.

R: 10. The manuscript notes the potential overheating of polypropylene during coating application. How do the temperature cycles affect polypropylene’s mechanical properties and structure? Please clarify whether any weakening of the mesh is expected from the coating process.

A: The authors are grateful to the Reviewer for the question. Yes, weakening of the mesh during the coating process is possible, but we plan to check this in the future.

Minor Comments and Suggestions:

R: 1. The manuscript contains some grammatical and syntactical errors. A thorough language edit is recommended to improve readability and comprehension.

A: The text of the manuscript was checked and corrected with the help of professional proofreading by a native speaker.

R: 2. Expand all acronyms upon their first use. For example, the term "CFU" should be defined (Colony-Forming Units) when initially introduced to aid readers less familiar with microbiological terminology.

A: Thanks for the recommendation! Fixed!

R: 3. Figures 2 and 3 could benefit from annotations or labels indicating critical features, such as coating layers or specific morphological characteristics. This would improve readers' ability to interpret the structural differences.

A: Figure 3 has been supplemented and provided with additional explanations.

R: 4. The manuscript references several studies in the introduction but could benefit from a clearer linkage to recent advancements in antimicrobial coatings for medical implants. Including more current studies (e.g., post-2020) on advances in coating technologies or infection resistance in biomaterials could provide a broader context for your work.

A: Section 1 has been expanded in accordance with the Reviewer's recommendations and provides an overview of silver- and copper-based antibacterial coatings.

Comments on the Quality of English Language

R: There are several grammatical errors and awkward phrasing throughout the manuscript. I recommend that the authors have the manuscript professionally proofread or thoroughly revised to ensure readability and clarity.

A: The text of the manuscript was checked and corrected with the help of professional proofreading by a native speaker.

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer’s comments

The present work investigates the possibility of modifying mesh polymer prostheses by applying a silver-containing nano-coating via magnetic spraying to increase their antibacterial effect. The study topic is very interesting and is a scientific addition in this field. The results obtained are derived from experimental procedures that were implemented with high professionalism and the discussion of the results is convincing. The manuscript is well prepared and in its current form is very good so it can be recommended for acceptance for publication in a journal Sci.

Comments for author File: Comments.pdf

Author Response

R2: Comments and Suggestions for Authors

Reviewer’s comments

R: The present work investigates the possibility of modifying mesh polymer prostheses by applying a silver-containing nano-coating via magnetic spraying to increase their antibacterial effect. The study topic is very interesting and is a scientific addition in this field. The results obtained are derived from experimental procedures that were implemented with high professionalism and the discussion of the results is convincing. The manuscript is well prepared and in its current form is very good so it can be recommended for acceptance for publication in a journal Sci.

A: The authors are grateful to the Reviewer for his attention to the manuscript and high assessment of the work.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors

I have read your work with interest and, in my opinion, it is worthy of publication. My main objection is that such a paper should show a more detailed study concerning the materials characterization and the influence of deposition parameters on the features of deposited materials. This is needed to evaluate the mechanisms for improving the material properties properly. I think this is worth considering in the following experiments. You have proven that using a specific combination of metal coatings improves the biocidal properties, but we do not know why that is the case. I also think that the paper needs significant improvements before it gets published. Here is a detailed list of my comments.

1.      Introduction

1.1 The volume of the introduction section is way too long, according to the topic. It was written with a lecturing style, concentrating too much on the basics instead of the current state of coatings manufacturing for biocidal activity. I do not see a point in:

·         listing endoprostheses manufacturers,

·         listing methods of endoprostheses production,

·         listing the properties of endoprostheses since the paper discusses antimicrobial properties only

·         keeping the fragment of health complications that long

·         such a thorough full explanation of enhancing the biocompatibility of endoprostheses

·         discussing in such an extensive manner materials for endoprostheses

I understand that the motivation behind the experiment is essential to be shown in the Introduction but not more as necessary; many of these issues are not studied in the experiment. An introduction should concentrate on the topic taken in the study. There are two pages of irrelevant information versus half of the page concerning the crucial technology of depositing metallic layers in a low-temperature regime.

1.2  What is MRS? No explanation is given about what is behind the abbreviation.

1.3  "Intensive overheating of the substrates does not allow increasing the sputtering rate by increasing the operating voltage." – Are you sure this is how your power system for magnetron sputtering works? The voltage during sputtering stabilizes as so-called breakdown voltage depending on the pressure, electrode distance, working gas, etc. Increasing the voltage at the power supply does not affect the breaking voltage significantly. Power growth is usually caused by increasing the current density from the power supply.

1.4  "In a magnetron sputtering system (MSS), secondary electrons are captured by a magnetic trap and do not bombard the substrate, which ensures its relatively low temperature." – I cannot agree. Magnetic field lines do not trap the whole population of glow discharge electrons, so they don't prevent the substrate from being bombarded by electrons. Some approaches limit plasma interaction with the substrate, but not entirely.

1.5  Discussion on various metals listed in Table 1 seems irrelevant to me

1.6  There are no references to latest studies in the field of this material systems Ag/Cu coatings on polymers deposited by magnetron sputtering.

 

2.      Materials and Methods

What is the carrier frequency of power during the sputtering? Is it 13.56 MHz (line 185) or 15 KHz (192)?

How was the "glow discharge operation realized? No information is given in the text.

What was the motivation for using nitrogen as a sputtering gas? It is an uncommon approach.

3.      Results

3.1 Line 250 – 251: "(…) it was revealed that the coatings formed in an argon environment (sample N1) have a finer-grained structure (…)". Do you not have the impression that observed microrelief (wrinkles) is not a feature of the coating structure but a pattern that forms during the energetic interaction of plasma with the polymer? Your coatings are <100nm thin, but the wrinkles are ~10 µm wide. I cannot explain their creation from the coating that is that thin. Is there an SEM image of the uncoated mesh that can be used to compare the surfaces?

3.2 Since any differences in the structure of the surface were observed, like coatings created during the deposition in Ar versus N₂, they should also be interpreted. Why the samples deposited from N₂ are more wrinkled?

3.3 Fig. 3. I cannot figure out what is actually on the images from the text and captions. Are there both Ag+Cu coatings or not? A description is confusing. Explain also the differences in structures.

3.4 Fig. 4 explains observed differences. Why is there more Cu content on the back side of the mesh?

3.5 lines 277 – 282. So, was a pulsating operation applied to all the processes? Would it be worth adding that information to the Material and Methods section?

3.6 line 282 – spraying – a common mistake for online translators for sputtering

3.7 line 286 "The coating thickness was determined by the coating formation parameters." How is that possible? Also, there is no need to give numbers for thickness with two decimal places.

3.8 EDS study – The problem with the EDS on thin layers is that it analyses the signal from a relatively significant layer volume and the substrate. That is why we should look for different methods instead. However, if there are no optional techniques, we should discuss the results according to each sublayer layer's thickness. I want to encourage the authors to reconstruct Table 3. Remove the Ar column. Add a column with the thickness of each sublayer. Simplify the decimal places in values. Again, the results will be analyzed according to the sublayer thickness. Give all needed explanations of the differences. I also find all the assumptions about "mixing"/diffusing specific elements to the surface speculative. EDS sees elements as well as good deep below the surface as on the surface (see the high C content).

3.9 There is no reference to the results in the literature. Where are the biocidal properties of coatings fabricated by the authors compared with other works? Are they comparable? Better?

Author Response

R3: Comments and Suggestions for Authors

Dear authors

R: I have read your work with interest and, in my opinion, it is worthy of publication. My main objection is that such a paper should show a more detailed study concerning the materials characterization and the influence of deposition parameters on the features of deposited materials. This is needed to evaluate the mechanisms for improving the material properties properly. I think this is worth considering in the following experiments. You have proven that using a specific combination of metal coatings improves the biocidal properties, but we do not know why that is the case. I also think that the paper needs significant improvements before it gets published. Here is a detailed list of my comments.

A: The authors are grateful to the Reviewer for the high evaluation of the work and a number of valuable recommendations to improve the quality of the manuscript. Of course, since the work is only at the beginning, we were not able to consider all aspects of this topic, but in the future the authors plan to continue this work. A number of experiments have already been conducted, the results of which we plan to present in subsequent publications.

1. Introduction

R: 1.1 The volume of the introduction section is way too long, according to the topic. It was written with a lecturing style, concentrating too much on the basics instead of the current state of coatings manufacturing for biocidal activity. I do not see a point in:

• listing endoprostheses manufacturers,
• listing methods of endoprostheses production,
• listing the properties of endoprostheses since the paper discusses antimicrobial properties only
• keeping the fragment of health complications that long
• such a thorough full explanation of enhancing the biocompatibility of endoprostheses
• discussing in such an extensive manner materials for endoprostheses

I understand that the motivation behind the experiment is essential to be shown in the Introduction but not more as necessary; many of these issues are not studied in the experiment. An introduction should concentrate on the topic taken in the study. There are two pages of irrelevant information versus half of the page concerning the crucial technology of depositing metallic layers in a low-temperature regime.

A: Thank you for your comment. The introduction substantiated the object of the study (mesh for hernioplasty), as well as the method of forming the coating. In addition, the new version of the publication contains an expanded justification for the choice of the coating composition. A semantic analysis of publications indexed in Scopus was conducted with the keywords “mesh”, “hernioplast”, “antibacterial”. It was possible to find and analyze about 40 articles. Most of them are written by medical works and describe the experience of clinical use of products and complications arising from their use. In connection with this, the authors considered that this article needs more detailed review information describing the essence of the problem and possible directions for its solution. We believe that such information will allow us to more reasonably formulate the goals and objectives of the study, as well as substantiate the scientific novelty of this work.

R: 1.2  What is MRS? No explanation is given about what is behind the abbreviation.

A: The typo has been corrected. The authors apologize.

R: 1.3  "Intensive overheating of the substrates does not allow increasing the sputtering rate by increasing the operating voltage." – Are you sure this is how your power system for magnetron sputtering works? The voltage during sputtering stabilizes as so-called breakdown voltage depending on the pressure, electrode distance, working gas, etc. Increasing the voltage at the power supply does not affect the breaking voltage significantly. Power growth is usually caused by increasing the current density from the power supply.

A: Since this phrase does not carry the key meaning for the article and, at the same time, contains a reason for discussion that is not within the scope of this article, we decided to remove this phrase without prejudice to the understanding of the article.

 

R: 1.4  "In a magnetron sputtering system (MSS), secondary electrons are captured by a magnetic trap and do not bombard the substrate, which ensures its relatively low temperature." – I cannot agree. Magnetic field lines do not trap the whole population of glow discharge electrons, so they don't prevent the substrate from being bombarded by electrons. Some approaches limit plasma interaction with the substrate, but not entirely.

A: Since this phrase does not carry the key meaning for the article and, at the same time, contains a reason for discussion that is not within the scope of this article, we decided to remove this phrase without prejudice to the understanding of the article.

R: 1.5  Discussion on various metals listed in Table 1 seems irrelevant to me

A: The authors understand the Reviewer's position, but believe that the information contained in Table 1 is useful for better understanding the properties of various materials and their deposition characteristics. We would like to retain this table.

 

R: 1.6  There are no references to latest studies in the field of this material systems Ag/Cu coatings on polymers deposited by magnetron sputtering.

A: A careful examination of the SCOPUS data on this topic revealed very few articles, mostly related to the topic of solar cell production. References to these articles and the corresponding references have been added.

Zakharov, A.N., Kovsharov, N.F., Oskomov, K.V., Rabotkin S.V., Solovyev, A.A., Sochugov, N.S. Properties of low-emission coatings based on ag and cu deposited on polymer film by magnetron sputtering. Inorganic Materials: Applied Research, 2012, 3(5), 433–439

 

Sendova-Vassileva, M., Dikov, H., Popkirov, G., Lazarova E., Gancheva V., Grancharov G., Tsocheva D. Mokreva, P., Vitanov, P. Transparent back contacts for P3HT:PCBM bulk heterojunction solar cells. Journal of Physics: Conference Series, 2014, 514(1), 012018

 

Chung, Y.M., Jung, M.J., Han, J.G. Mechanical Properties of Ti-Me-N Coated Polymer. IEEE International Conference on Plasma Science, 2003, 424

 

 

 

 

2. Materials and Methods

R: What is the carrier frequency of power during the sputtering? Is it 13.56 MHz (line 185) or 15 KHz (192)?

A: Magnetron output data has been clarified. The error has been corrected. The frequency is 15 kHz. The authors apologize for the inattention.

R: How was the "glow discharge operation realized? No information is given in the text.

A: This process is implemented on the RITM-SP experimental setup, the corresponding references have been added (to Table 2).

Meisner, S.N., Meisner, L.L. Effects of Electron Beam Processing on Fatigue Fracture Propagation Pattern and Formation of Deformation Zone on the Fracture Surface in Titanium Nickelide. Inorganic Materials: Applied Research, 2023, 14(5-6), 1141–1151

Fedorov, S.V., Aleshin, S.V., Swe, M.H., Abdirova, R.D. Kapitanov, A.V., Egorov, S.B. Comprehensive surface treatment of high-speed steel tool. Mechanics and Industry, 2017,18(7), 2017066

 

R: What was the motivation for using nitrogen as a sputtering gas? It is an uncommon approach.

A: Our team of authors has extensive experience in depositing coatings of pure metals (argon is used as the working gas for this process) and nitride coatings (nitrogen is used as the working gas for this process) on various metal products of mechanical engineering and other industries. Nitride coatings are characterized by high strength, hardness and chemical resistance (including in aggressive environments of the human body) due to the formation of a cubic face-centered structure. In the proposed article, we consider a new area of ​​possible application of coatings for our group - polymers for medical purposes. We proceeded from the assumption that nitride coatings, having a set of valuable properties, can also be effectively used in this area.

 

3. Results

R: 3.1 Line 250 – 251: "(…) it was revealed that the coatings formed in an argon environment (sample N1) have a finer-grained structure (…)". Do you not have the impression that observed microrelief (wrinkles) is not a feature of the coating structure but a pattern that forms during the energetic interaction of plasma with the polymer? Your coatings are <100nm thin, but the wrinkles are ~10 µm wide. I cannot explain their creation from the coating that is that thin. Is there an SEM image of the uncoated mesh that can be used to compare the surfaces?

A: The authors agree with the Reviewer - the statement about "finer-grained structure" requires additional research, so the phrase was changed to: " Thus, the (Ag,Cu) coatings formed in an argon environment (sample N1) have a relief with more frequent and fine ribbing (Figures 2c, 2e, 2g) than those formed in a nitrogen environ-ment (sample N4 – Figures 2d, 2f, 2h). "

R: 3.2 Since any differences in the structure of the surface were observed, like coatings created during the deposition in Ar versus N₂, they should also be interpreted. Why the samples deposited from N₂ are more wrinkled?

A: Unfortunately, this issue requires further research. The first idea is the difference in temperature, depending on which a more or less pronounced warping of the polymer substrate occurs. However, the plasma flow (argon or nitrogen) can have a significant effect. The following sentence has been added to the text of the manuscript: «The reasons for the more pronounced wavy relief in samples formed in a nitrogen environment require separate study and may lie both in the difference in temperatures and in the characteristics of the plasma flows».

R: 3.3 Fig. 3. I cannot figure out what is actually on the images from the text and captions. Are there both Ag+Cu coatings or not? A description is confusing. Explain also the differences in structures.

A: Figure 3 has been supplemented with images that allow a better understanding of the coating structure, designations of the polymer substrate and coating layers have been added, and the description has been expanded and modified accordingly.

 

R: 3.4 Fig. 4 explains observed differences. Why is there more Cu content on the back side of the mesh?

A: This effect is explained by the fact that the coating is layered: a layer of copper on the polymer, and then a layer of silver. The polymer is transparent enough, so the copper on the back side shines through it.

R: 3.5 lines 277 – 282. So, was a pulsating operation applied to all the processes? Would it be worth adding that information to the Material and Methods section?

A: The authors agree and are grateful to the reviewer for the recommendation. Information added.

R: 3.6 line 282 – spraying – a common mistake for online translators for sputtering

A: The authors agree and are grateful to the reviewer for pointing out the inaccuracy. The term "spraying" has been replaced with "sputtering".

R: 3.7 line 286 "The coating thickness was determined by the coating formation parameters." How is that possible? Also, there is no need to give numbers for thickness with two decimal places.

A: The wording has been changed to: «The coating thickness was determined by the deposition time». Excessive decimal places have been removed (The authors agree with the Reviewer; it is hardly possible to talk about an accuracy of more than 1 nm here). It is impossible to remove extra decimal places directly in the Figure (they are determined by the program), but changes have been made in the text.

R: 3.8 EDS study – The problem with the EDS on thin layers is that it analyses the signal from a relatively significant layer volume and the substrate. That is why we should look for different methods instead. However, if there are no optional techniques, we should discuss the results according to each sublayer layer's thickness. I want to encourage the authors to reconstruct Table 3. Remove the Ar column. Add a column with the thickness of each sublayer. Simplify the decimal places in values. Again, the results will be analyzed according to the sublayer thickness. Give all needed explanations of the differences. I also find all the assumptions about "mixing"/diffusing specific elements to the surface speculative. EDS sees elements as well as good deep below the surface as on the surface (see the high C content).

A: Unfortunately, in this case we did not have the opportunity to use a more accurate method than EDS. Values ​​are rounded to one decimal place. The Ar column has been removed, the authors agree with the Reviewer that it is not possible to accurately measure argon content using this method. The Ag content in the coating composition is in obvious correlation with the thickness of the Ag layer in the coatings. The greater the thickness of the Ag layer, the higher the content of this element.

Table 3 has been supplemented and the description has also been supplemented.

R: 3.9 There is no reference to the results in the literature. Where are the biocidal properties of coatings fabricated by the authors compared with other works? Are they comparable? Better?

A: In accordance with the Reviewer's recommendations, the section on the results of studies of the antibacterial properties of coatings containing Ag and/or Cu has been expanded in the Introduction. The purpose of this paper was to study the possibility of forming antibacterial coatings on a polypropylene substrate using magnetron sputtering. Unfortunately, we were unable to find any articles on polymer networks with coatings containing Ag and/or Cu formed by magnetron sputtering to conduct these comparisons (several articles on magnetron sputtering of coatings containing Ag and/or Cu on polymers relate to the production of solar battery elements - see above). In addition, the work did not aim to compare the properties of coatings obtained by different methods, but only considered the possibility of achieving the result of antibacterial coatings obtained by magnetron sputtering. In the future, we will try to take into account the Reviewer's recommendation and conduct comparative tests.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for taking into account the suggestion of this reviewer. Most of the changes have been done, and the rest have been justified clearly. The revised article can be published in its current form.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors

Thank you for your time and efforts to consider my entire review helpfull to rise the quality of the paper