Biosynthesis of Zinc Oxide Nanoparticles Using Garlic Peel Extract and Their Antibacterial Potential

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors present an interesting study on the biosynthesis of zinc oxide nanoparticles (ZnO NPs) using garlic peel extract. Although the study is clear, well-written, and well-structured, I have some suggestions and questions that could further enhance the quality and comprehensiveness of the paper:

 

1. Initial Inoculum for Antibacterial Assay: The manuscript does not specify the initial inoculum of bacteria used in the antibacterial assay. Including this information in the Materials and Methods section would be beneficial for the reproducibility of the results.

 

2. Antimicrobial Quantitative Assay: To strengthen the findings on antibacterial activity, it is recommended to conduct an antimicrobial quantitative assay in triplicate at least. This will provide more robust data and allow for statistical validation of the results.

 

3. Figure 2 and Nanoparticle Morphology: The authors state that the ZnO NPs have a spherical surface in the abstract. However, Figure 2 shows that the nanoparticles have an irregular surface. This discrepancy should be addressed by either revising the description in the abstract or improving the quality and clarity of Figure 2 to reflect the actual morphology of the nanoparticles better.

 

4. Antioxidant Assay Comparison: The antioxidant assay results could be more informative if the authors had tested under the same conditions as the antimicrobial assay, specifically including negative control (1), plant extract (2), zinc sulfate (3), and ZnO NPs (4). This would provide a clearer understanding of the relative antioxidant activity of ZnO NPs compared to the plant extract and zinc sulfate alone.

 

5. Cytotoxicity of ZnO NPs: In conclusion, the authors suggest potential applications of ZnO NPs in food and medicine. However, the manuscript does not discuss the cytotoxicity of ZnO NPs in contact with human cells. It would be important to include any cytotoxicity assays performed, or at least discuss the potential cytotoxic effects, to assess the safety of ZnO NPs for these applications.

 

6. Comparison with Other Studies: Adding a discussion that compares the results of this study with other studies involving metal nanoparticles synthesized using plant extracts would enhance the context and relevance of your findings. This could include a comparison of nanoparticle size, shape, antibacterial, and antioxidant activities, and any other relevant properties.

 

Incorporating these suggestions would improve the scientific rigour and depth of the study, making it a more valuable contribution to the field.

Comments on the Quality of English Language

Minor editing of English

Author Response

Comments Reviewers 1

1. Initial Inoculum for Antibacterial Assay: The manuscript does not specify the initial inoculum of bacteria used in the antibacterial assay. Including this information in the Materials and Methods section would be beneficial for the reproducibility of the results.

Response: the initial inoculum of bacterial strains have been added in the methodology as CFU/ml

Comments 2

2. Antimicrobial Quantitative Assay: To strengthen the findings on antibacterial activity, it is recommended to conduct an antimicrobial quantitative assay in triplicate at least. This will provide more robust data and allow for statistical validation of the results.

Response: Indeed, the experiments were conducted in three replicates and this was mentioned in the methodology (please see Line 179)

Line 179: The experiments were done in triplicates and the results of the antibacterial activity of ZnO NPs were expressed as mean± SD  (please see Result section)

Comments 3

3. Figure 2 and Nanoparticle Morphology: The authors state that the ZnO NPs have a spherical surface in the abstract. However, Figure 2 shows that the nanoparticles have an irregular surface. This discrepancy should be addressed by either revising the description in the abstract or improving the quality and clarity of Figure 2 to reflect the actual morphology of the nanoparticles better.

Response:  The surface shape of the synthesized ZnO NPs was modified from spherical to irregular in the abstract and the results sections

Comments 4

4. Antioxidant Assay Comparison: The antioxidant assay results could be more informative if the authors had tested under the same conditions as the antimicrobial assay, specifically including negative control (1), plant extract (2), zinc sulfate (3), and ZnO NPs (4). This would provide a clearer understanding of the relative antioxidant activity of ZnO NPs compared to the plant extract and zinc sulfate alone.

Response:  the antioxidant activity of zinc sulfate was estimated and included in Figure 7.  On the other han, with respect to the negative control: the DPPH method relies on the use of a negative control, which is used in the equation to calculate the percentage of the free radical scavenging activity or % of DPPH inhibition.

% of DPPH inhibition= (( A0 – As)/A0)×100

Where A0 refers to the control reading and As refers to the sample reading at 517 nm to determine % of inhibition.  (please see material and methods section)

Plant extract: regarding the plant extract, we used a crud aqueous extract for the biosynthesis of nanoparticles, thus it was not possible to prepare different concentrations of it to estimate its antioxidant activity. (please see material and methods section)

Comments 5

5. Cytotoxicity of ZnO NPs: In conclusion, the authors suggest potential applications of ZnO NPs in food and medicine. However, the manuscript does not discuss the cytotoxicity of ZnO NPs in contact with human cells. It would be important to include any cytotoxicity assays performed, or at least discuss the potential cytotoxic effects, to assess the safety of ZnO NPs for these applications.

 Response: it has been discussed in the section of antibacterial activity (please see Results and conclusion sections).

Comments

6. Comparison with Other Studies: Adding a discussion that compares the results of this study with other studies involving metal nanoparticles synthesized using plant extracts would enhance the context and relevance of your findings. This could include a comparison of nanoparticle size, shape, antibacterial, and antioxidant activities, and any other relevant properties.

Response: results of other studies were added in the discussion of several sections including:

Biosynthesis of nanoparticles using plant extract, SEM (shape), the size of ZnO NPs, Antibacterial activity, and Antioxidant activity (please see discussion section).

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The author has done a good job with current study including biosythesis of zinc oxide nanoparticles using garlic peel extract and assessing their antibacterial properties. The paperis well written and elaborated extensively such that it is easily understandable by the readers.

I have a couple minor suggestions for the author;

1. The DPPH radical scavending assay for analyzing the antioxidant property of nanoparticle is most extensively used but their is another assay called FRAP assay which could also be done to compare the results. I dont know if author knows about it or they just wanted to do DPPh assay.

2. I personally like to see the molecular docking resultd on a 2D platform as it makes it easy for the reader to see the bonds and binding enerrgies clearly between two aminoacids. I have used Ligplot to do so. May be author could consider to do that. Its just a suggestion, but it would add extra value to the paper.

3. Test corrections:

      Line 150 - "As well as" can be written as "ALso", as it makes more sense when you read it.

      Line 178 - "Socked" with "Soaked" 

4. Some places like in Line 205, the author has mentioned a reference as a numer, may be they should write First author's name et al. and then mention the reference as a number.

Author Response

SECOND REWIERS

Comments 1

1. The DPPH radical scavending assay for analyzing the antioxidant property of nanoparticle is most extensively used but their is another assay called FRAP assay which could also be done to compare the results. I dont know if author knows about it or they just wanted to do DPPh assay.

Response: Both DPPH and FRAP are used for determination of antioxidant activity, however, DPPH assay is widely used to study the radical scavenging activity of green synthesized Nps.

Comments 2

2. I personally like to see the molecular docking resultd on a 2D platform as it makes it easy for the reader to see the bonds and binding enerrgies clearly between two aminoacids. I have used Ligplot to do so. May be author could consider to do that. Its just a suggestion, but it would add extra value to the paper.

Response: We appreciate the recommendation. We do not agree with the necessity of integrating 2D platform into the analysis. Although I acknowledge that 2D platform (such as LigPlot, Discovery Studio Visualizer) is a compelling element in illustrating the connections and binding energies distinctly between two amino acids, the interactions in the present research focus solely on hydrogen bonds between the ZnO nanoparticles and the amino acids. Instead, we have adjusted Figures 8 & 10 to facilitate the reader in identifying the established polar bonds between the ZnO nanoparticles and the targeted proteins.

Comments 3

3. Test corrections:

 

      Line 150 - "As well as" can be written as "ALso", as it makes more sense when you read it.

 

      Line 178 - "Socked" with "Soaked"

Response: it has been modified as mentioned above.

Comments 4

4. Some places like in Line 205, the author has mentioned a reference as a numer, may be they should write First author's name et al. and then mention the reference as a number.

Response: it has been modified as mentioned above (please see references 28 and 29).

 

 

 

 

Author Response File: Author Response.docx