Ag-Containing Carbon Nanocomposites: Physico-Chemical Properties and Antimicrobial Activity

Round 1

Reviewer 1 Report

1. It must be necessarily emphasized in the paper how the described research focuses on environmental, social and economic goals of sustainability.  

2. The paper is too long. The discussion should be more concise, brief, especially the part concerning the analysis of nano structures (lines 283 – 404) is worded in a long-winded way.

3. I think it would be good to compare the antibacterial activity of obtained composites with standard antibiotics against Gram‐negative and Gram‐positive bacteria.

Minor editing of English language required

Author Response

We would like to thank the reviewer for the time spent on the review, and the insightful, constructive comments towards improving our manuscript. All remarks were taken into account in the revised version of the manuscript. The corrections in the text of the manuscript were marked with color. Detailed point-by-point response to comments were given separately.

Reviewer 1

It must be necessarily emphasized in the paper how the described research focuses on environmental, social and economic goals of sustainability.

Authors' response: Additional information describing the environmental, social and economic sustainability objectives of the work has been added to the Introduction and Conclusion section.

2. The paper is too long. The discussion should be more concise, brief, especially the part concerning the analysis of nano structures (lines 283 – 404) is worded in a long-winded way.

Authors' response: The part of text has been edited and shortened.

3. I think it would be good to compare the antibacterial activity of obtained composites with standard antibiotics against Gram‐negative and Gram‐positive bacteria.

Authors' response: The antibiotic susceptibility of bacterial strains from the ATCC collection selected for testing is well described. However, before starting our experiments, we determined the sensitivity to cefepime (4^th generation cephalosporin) using the disc diffusion method.

The tested strains were sensitive to cefepime, except Acinetobacter, the growth inhibition zones were: E. coli 33 mm, S. aureus 28 mm, P. aeruginosa 26 mm, K. pneumoniae 24 mm and A. baumanii 14 mm.

We hope that the revised version of the article fulfils the requirements.

Author Response File: Author Response.docx

Reviewer 2 Report

In the manuscript entitled “Ag-CONTAINING CARBON NANOCOMPOSITES: PHYSICO-CHEMICAL PROPERTIES AND ANTIMICROBIAL ACTIVITY” the authors reported the development of a nanostructured hybrid Ag-containing carbon sorbent with antimicrobial activity. The study is interesting, but I highlighted some points that can be taken into consideration by the authors to improve the manuscript. The introduction can be more specific and the discussion of results must be based on data published in the scientific literature.

1. Line 18: It is important to avoid using too many acronyms in the manuscript abstract.

2. Lines 22-23: Please, include the scientific name of the bacteria in full (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii).

3. Lines 24-26: I suggest including the main results (inhibition zones) of the antimicrobial activity of the synthesized composites. This will make the abstract more attractive to the reader.

4. Lines 31-125: The introduction is very long and comprehensive. I suggest that authors be more specific in presenting the manuscript.

5. Lines 134-136: Why did the authors choose the Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii strains to carry out the antimicrobial tests? Are all these microorganisms identified as potential water contaminants? It is important to justify this in the text.

6. Lines 211-221: Didn't the authors follow another well-established methodology in the literature to evaluate the antimicrobial activity of carbon composites? Please, cite the reference.

7. Lines 471-518: This information included in the manuscript results must be discussed based on evidence and data published in the scientific literature.

8. In the conclusion section, I suggest that the authors make clear the practical application of the carbon composites developed in this study. In which sector can they be applied? Can they be used on a large scale for water disinfection? What are the costs and benefits?

Author Response

We would like to thank the reviewer for the time spent on the review, and the insightful, constructive comments towards improving our manuscript. All remarks were taken into account in the revised version of the manuscript. The corrections in the text of the manuscript were marked with color. Detailed point-by-point response to the comments were given separately.

Reviewer 2

The introduction can be more specific and the discussion of results must be based on data published in the scientific literature.

Authors' response: The "Introduction" section was edited according to the comments of the reviewers and summarized.

MG 1. Line 18: It is important to avoid using too many acronyms in the manuscript abstract.

Authors' response: Abstract was edited.

MG 2. Lines 22-23: Please, include the scientific name of the bacteria in full (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii). 

Authors' response: The scientific name of the bacteria in full was added in the Antibacterial Activity Determination section.

3. Lines 24-26: I suggest including the main results (inhibition zones) of the antimicrobial activity of the synthesized composites. This will make the abstract more attractive to the reader.

Authors' response: Thank you, this fragment was edited.

4. Lines 31-125: The introduction is very long and comprehensive. I suggest that authors be more specific in presenting the manuscript.

Authors' response: The Introduction section was revised and summarized.

5. Lines 134-136: Why did the authors choose the Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, andAcinetobacter baumannii strains to carry out the antimicrobial tests? Are all these microorganisms identified as potential water contaminants? It is important to justify this in the text.

Authors' response: The bacterial strains selected for our tests come from the ATCC ( American Type Culture Collection) and are standardly used in drug sensitivity tests and other antibacterial compounds according to EUCAST recommendation (The European Committee on Antimicrobial Susceptibility Testing).

Strains S. aureus ATCC 25923 and E. coli ATCC 25922 (susceptible phenotypes) are commonly used as a control strain for susceptibility testing to antibiotics. E. coli is a species of fecal coliform bacteria that has a direct link to water quality, and it is used as a measure of microbial contamination of water quality level.

1. pneumoniae, P. aeruginosa and A. baumannii are multidrug resistant opportunistic pathogens that can cause nosocomial infections. Mechanisms of antibiotic resistance are described for the remaining strains K. pneumoniae ATCC 700603 ( ESBL positive SHV-18 producing), P. aeruginosa ATCC 27853 (inducible AmpC β-lactamase), A. baumanii ATCC 19606 (β-lactam resistant, susceptible to third-generation cephalosporins and carbapenems).

We found it advisable to check the activity of nanoparticles against drug-resistant strains of bacteria due to the fact that several recent studies have reported the development of bacterial resistance to broad-spectrum antimicrobial silver nanoparticles [Mc Neilly et al. 2023*]. Moreover, the main mechanisms of action of AgNPs have been confirmed and described for these strains [Taha et al. 2020**]

*McNeilly O, Mann R, Cummins ML, Djordjevic SP, Hamidian M, Gunawan C. Development of Nanoparticle Adaptation Phenomena in Acinetobacter baumannii: Physiological Change and Defense Response. Microbiol Spectr. 2023 Feb 14;11(1):e0285722. doi: 10.1128/spectrum.02857-22

** Taha, A.; Ben Aissa, M.; Da’na, E. Green Synthesis of an Activated Carbon-Supported Ag and ZnO Nanocomposite for Photocatalytic Degradation and Its Antibacterial Activities. Molecules 2020, 25, 1586, doi:10.3390/molecules25071586.

6. Lines 211-221: Didn't the authors follow another well-established methodology in the literature to evaluate the antimicrobial activity of carbon composites? Please, cite the reference.

Authors' response:

Appropriate literature references to the method was added.

Balouiri M, Sadiki M, Ibnsouda SK. Methods for in vitro evaluating antimicrobial activity: A review.

J Pharm Anal. 2016 Apr;6(2):71-79. doi: 10.1016/j.jpha.2015.11.005.

Rajeshkumar S, Malarkodi C. In Vitro Antibacterial Activity and Mechanism of Silver Nanoparticles against Foodborne Pathogens. Bioinorg Chem Appl. 2014;2014:581890. doi: 10.1155/2014/581890.

7. Lines 471-518: This information included in the manuscript results must be discussed based on evidence and data published in the scientific literature.

Authors' response: Appropriate literature references to the method was added.

8. In the conclusion section, I suggest that the authors make clear the practical application of the carbon composites developed in this study. In which sector can they be applied? Can they be used on a large scale for water disinfection? What are the costs and benefits?

Authors' response: Additional information was added to the Introduction and Conclusion section. The benefits of approaches and methods for synthesising carbon composites and raw materials as a carbon source is discussed.

We hope that the revised version of the article fulfils the requirements.

Author Response File: Author Response.docx

Reviewer 3 Report

This paper developed a successful procedure for synthesis of Ag-containing carbon nano-sorbents, and analyzed the structural and morphological properties of the resulting composites, and further studied their practical application in water purification and disinfection. Altogether, this study is organized well. However, there are several flaws should be addressed.

 1. In Abstract: it is batter to provide the full names of the microbes mentioned in lines 22-23, like listed in lines 213-215.

2. The ‘Silver NPs’ in line 102 should be ‘silver nanoparticles (AgNPs)’ because of its first appearance. And subsequently, ‘silver nanoparticles (AgNPs)’ in line 109 could be abbreviated as ‘AgNPs’.

3. The sentence “4-chlorophenol (≥99%, Sigma-Aldrich).” in line 132 is incomplete and need to rewrite.

4. Some bars or scales in Figure 4 in page 8 are unclear.

Author Response

We would like to thank the reviewer for the time spent on the review, and the insightful, constructive comments towards improving our manuscript. All remarks were taken into account in the revised version of the manuscript. The corrections in the text of the manuscript were marked with color. Detailed point-by-point response to comments were given separately.

Reviewer 3

1. In Abstract: it is batter to provide the full names of the microbes mentioned in lines 22-23, like listed in lines 213-215.

Authors' response: The fragment was edited

2. The ‘Silver NPs’ in line 102 should be ‘silver nanoparticles (AgNPs)’ because of its first appearance. And subsequently, ‘silver nanoparticles (AgNPs)’ in line 109 could be abbreviated as ‘AgNPs’.

Authors' response: Thank you for your comments, the error was corrected.

3. The sentence “4-chlorophenol (≥99%, Sigma-Aldrich).” in line 132 is incomplete and need to rewrite.

Authors' response: The fragment was edited.

4. Some bars or scales in Figure 4 in page 8 are unclear.

Authors' response:  Figure 4 was edited.

We hope that the revised version of the article fulfils the requirements.

Reviewer 4 Report

The authors synthesized a series of Ag-containing carbon sorbents and analyzed their structural and morphological properties, the performance of composites was thereafter tested via adsorption of phenolic derivative 4-chlorophenol and antibacterial against both Gram-positive and Gram-negative pathogens. This work is well organized and structured, with enough experimental and analytical data supporting the key points raised by the authors. Thus, I suggest the acceptance of this paper after carefully considering the following comments:

1.    Sample synthesis, on what basis did the author choose the content of AgNO3 of 0.2, 0.5 and 1 mmol/g?

2.    Table 1, citations should be included for all theoretical models correspondingly.

3.    Figure 4f, What does 0.236 nm mean? lattice fringe for facet (111)? If so, slight difference from 0.235 nm in Figure 4e, could it be the measurement error?

4.    Figures 6 and 8, both figures should be rearranged to enable more clearly presentation.

5.    For carbon-based materials on pollutant adsorption anti antimicrobial applications, some new references are suggested for a broader readership, e.g., 10.1016/j.carbpol.2023.120537; 10.1039/d1nh00633a.

Author Response

We would like to thank the reviewer for the time spent on the review, and the insightful, constructive comments towards improving our manuscript. All remarks were taken into account in the revised version of the manuscript. The corrections in the text of the manuscript were marked with color. Detailed point-by-point response to the comments were given separately.

Reviewer 4

1. Sample synthesis, on what basis did the author choose the content of AgNO₃ of 0.2, 0.5 and 1 mmol/g?

Authors' response:  Based on our previous research, the proposed concentrations allow to obtain samples with a uniform distribution of the modifier in the silica matrix. And this, in turn, leads to a monodisperse uniform distribution of particles in the matrix. Thus, small concentrations of the modifier make it possible to obtain X-ray amorphous active nanoparticles that have high bactericidal properties.

2. Table 1, citations should be included for all theoretical models correspondingly.

Authors' response: Relevant references have been added in the Table 1.

3. Figure 4f, What does 0.236 nm mean? lattice fringe for facet (111)? If so, slight difference from 0.235 nm in Figure 4e, could it be the measurement error?

Authors' response: Thank you for your comment. Yes, it was incorrectly stated. The fragment was edited. Figure 4 was corrected.

4. Figures 6 and 8, both figures should be rearranged to enable more clearly presentation.

Authors' response: Figure 6 and Figure 8 were rearranged and compressed.

5. For carbon-based materials on pollutant adsorption antimicrobial applications, some new references are suggested for a broader readership, g., 10.1016/j.carbpol.2023.120537; 10.1039/d1nh00633a.

Authors' response: The link was added to the text.

We hope that the revised version of the article fulfils the requirements.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors completed all my recommendations.