Study on the ZrN/Ag₂O Micro–Nano Gradient Composite Structure Constructed on Pure Ti for Biomaterials

Round 1

Reviewer 1 Report

The paper is a typical material chemistry study. TIn et al. developed ZrN/Ag₂O which can be introduced as a coating material for implants in the medical use. The material was characterized by several methods as (SEM, XRD, etc), along with cytotoxicity and activity against bacteria. 

The authors repeat several times the word "finely". Hope it's a typo and they meant "finally". 

The labeling of Figure 9, in particular b and c should be enlarged and updated before publication. 

Generally, paper is well written and might find readers. Experiments well described. Conclusions supported by the results.

The paper is publishable after a minor revision.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The 16-page article contains 11 figures, 3 tables and 39 references.

     This article is devoted to the preparation and study of a biocompatible ZrN / Ag2O coating in the form of a composite structure on pure titanium. The Ag2O component allows for increased cytocompatibility with controlled release of Ag + compared to metals, and ZrN is expected to provide high hardness, wear resistance and corrosion resistance of the coating.

1. The content of the work to a certain extent corresponds to the subject and profile of the journal.
2. The originality and novelty of the material proposed by the authors of the article are at a good level. Nitride coatings based on TiN and ZrN, including multilayer and multicomponent ones, have been known for a long time and are used in various fields. At the same time, the ZrN / Ag2O combination obtained by the ion implantation method is relatively new. An original proposal is also on the use of Ag2O to increase cytocompatibility upon release of Ag + in comparison with silver alloys.
3. The theoretical and practical significance of the work is due to the possibility of using the results obtained in the article in the conduct of research and development and R&D, associated with an increase in the properties of already produced implants from first-generation alloys (pure titanium and its traditional alloys).
4. The quality of the analysis of the problem and the validity of its relevance in the introductory part of the manuscript are at a good level.
5. The task has been completely solved.
6. Discussion of the reviewed literature data was carried out in accordance with existing scientific concepts.
7. The consistency (consistency) of the presentation does not require revision to the standard requirements of scientific journals.
8. The literacy of the presentation is sufficiently good, the style of presentation corresponds to the scientific nature of the material, and the terminology used is accepted.
9. The design of the article and its volume correspond to the accepted norms, figures and tables correspond to the stated topic and are appropriate for illustrating the text, most of the literary sources are recent publications in specialized scientific journals. The degree of self-citation is acceptable.

 

Notes:

There are no significant fundamental remarks on the content of the article. There are a number of clarifying notes on some of the authors' conclusions:

1. The studied ZrN / Ag2O coating is composite, but the use of the term “multilayer” is not entirely correct. Such a term could be used if there were other layers in addition to the ZrN layer. In this case, the ZrN coating after implantation of Ag + ions is usually designated as gradient.
2. At the end of the section “1. Introduction ”(page 2, lines 94-94) there is a sentence“ The results show that the newly developed ZrN / Ag2O multifunctional coating can finely satisfy the requirement of the metallic implants in clinical application. ” This formulation is not entirely correct. Already developed and industrially produced alloys of the second generation for implants (the article "Assessment of mechanical, chemical, and biological 3 properties of Ti-Nb-Zr alloy for medical applications" was recently published in Materials), for which such a coating is no longer required. Even more advanced third-generation biocompatible alloys are currently being developed. In addition, the use of ceramic coatings always carries the risk of cracking and flaking. Therefore, it is better for the authors to more objectively reflect the fact that their coating can improve the consumer properties of implants made of pure titanium or Ti-6Al-4V alloys.
3. Section 3.1 (page 7, lines 244-248) states that “Ag exists exactly in the oxidized state (Ag2O phase) on the surface layer”. However, it does not explain why all the available silver has oxidized. According to the results obtained by the authors, it would be correct to indicate that «Ag exists exactly in the oxidized state (Ag₂O phase) on coating surface.»

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

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Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Dear Authors,

The results presented are important and should be published. However, my major concerns are the descriptions of the methods, especially ICP-MS for determination of silver ions release. In addition, references for in vitro antibacterial evaluation and silver ions release are missing.

In addition, and in more detail, other concerns are:

Lines 10-25: In the abstract an introduction is missing and the used methods for testing are not stated. The description of the results in the abstract could be shorter.

Lines 34-35: What is meant by “so on”. It should be described in more detail.

Lines 54-57: The possible effects on eukaryotic cells should be describe in more detail.

Lines 94-95: The results should be summarized in the conclusions. Instead the importance of this study should be emphasizes.

Lines 150-152: The references for the method are missing. The names of bacteria should be in italic.

Lines 170-172: The method should be described in more detail. In addition, the reference for the method should be added.

Lines 188-189: It is not clear if the reference number 36 refers only to the Kc calculated or for the whole method. This should be specified.

Lines 390-391: E coli and S. aureus should be in italic.

Overall, mine suggestion is that the manuscript would be acceptable with major revision. Substantial changes should be carried out before acceptance.

Good luck

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 4 Comments

 

 

Point 1: The results presented are important and should be published. However, my major concerns are the descriptions of the methods, especially ICP-MS for determination of silver ions release. In addition, references for in vitro antibacterial evaluation and silver ions release are missing.

 

Response 1:

To examine the release behavior of Ag⁺ from the ZrN/Ag₂O composite coatings, each coated specimen was immersed in 10 mL Ringer’s solution at 37 ± 0.5°C. The solution containing the released Ag⁺ was sampled at time of 30 days and analyzed by inductively-coupled plasma mass spectroscopy (ICP-MS, Nexion 300X, PerkinElmer, Massachusetts, USA).

References for in vitro antibacterial evaluation and silver ions release have been added in the revised manuscript and are showed as below.

Liu, Y., Zhong, Z., Zara, J. N., et al. The antimicrobial and osteoinductive properties of silver nanoparticle/poly (DL-lactic-co-glycolic acid)-coated stainless steel[J]. Biomaterials, 2012, 33(34):8745-8756.

Li, J.H., Qiao, Y.Q., Zhu, H.Q., Meng, F.H., Liu, X.Y. Existence, release, and antibacterial actions of silver nanoparticles on Ag–PIII TiO2 films with different nanotopographies[J]. Int. J. Nanomed. 2014, 9, 3389-3402.

 

Point 2: Lines 10-25: In the abstract an introduction is missing and the used methods for testing are not stated. The description of the results in the abstract could be shorter.

 

Response 2: Following the reviewer’s suggestion, we have updated the abstract in the revised manuscript.

 

Point 3: Lines 34-35: What is meant by “so on”. It should be described in more detail.

 

Response 3: Following the reviewer’s suggestion, we have described “so on” in more detail in revised manuscript.

The revised “Lines 34-35” are showed as below:

However, their application and development are restricted to a certain extent by their poor hardness, wear resistance and antibacterial properties.

 

Point 4: Lines 54-57: The possible effects on eukaryotic cells should be describe in more detail.

 

Response 4: In fact, it has been reported that Ag-containing coatings can kill bacteria observably by the release of silver ions. The Ag-containing coatings can release silver ions and generate reactive oxygen species (ROS), which interact with membrane proteins affecting their correct function and facilitate the increase of membrane permeability and the loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication.

 

Point 5: Lines 94-95: The results should be summarized in the conclusions. Instead the importance of this study should be emphasizes.

 

Response 5: Following the reviewer’s suggestion, we have emphasized the importance of this study in the revised manuscript. The change is highlighted in red in the revised manuscript.

 

Point 6: Lines 150-152: The references for the method are missing. The names of bacteria should be in italic.

 

Response 6: Following the reviewer’s suggestion, we have added reference for in vitro antibacterial evaluation in the revised manuscript, and we have modified the names of bacteria to italic.

Liu, Y., Zhong, Z., Zara, J. N., et al. The antimicrobial and osteoinductive properties of silver nanoparticle/poly (DL-lactic-co-glycolic acid)-coated stainless steel[J]. Biomaterials, 2012, 33(34):8745-8756.

 

Point 7: Lines 170-172: The method should be described in more detail. In addition, the reference for the method should be added.

 

Response 7: Following the reviewer’s suggestion, we have added reference for in vitro antibacterial evaluation in the revised manuscript.

Li, J.H., Qiao, Y.Q., Zhu, H.Q., Meng, F.H., Liu, X.Y. Existence, release, and antibacterial actions of silver nanoparticles on Ag-PIII TiO₂ films with different nanotopographies[J]. Int. J. Nanomed. 2014, 9, 3389-3402.

 

Point 8: Lines 188-189: It is not clear if the reference number 36 refers only to the Kc calculated or for the whole method. This should be specified.

 

Response 8: Following the reviewer’s suggestion, the reference number 36 (number 38 in the revised manuscript) refers to the whole method, we have updated in the revised manuscript.

 

Point 9: Lines 390-391: E coli and S. aureus should be in italic.

 

Response 9: Following the reviewer’s suggestion, we have modified the names of bacteria to italic. The change is highlighted in red in the revised manuscript.

Author Response File: Author Response.docx

Round 2

Reviewer 4 Report

Dear Authors,

In my opinion the manuscript could be now acceptable for publication.

Good luck!