Zinc-Silver Doped Mesoporous Hydroxyapatite Synthesized via Ultrasonic in Combination with Sol-Gel Method for Increased Antibacterial Activity
, Pongtanawat Khemthong 6, Teera Butburee 6, Saran Youngjan 6, Jeremiah C. Millare 7 and Orrasa Prasitnok 8,*
Round 1
Reviewer 1 Report
The paper aims to develop a HA material doped with Zn-Ag using the ultrasonic assisted sol-gel technique. The obtained results are relevant for to predict the application area of these materials. The paper is well structured with appropriate content and references.
There are few comments:
- in the title is mentioned that the synthetised materials are appropriate for “increased bacterial activity in water purification”
- although the obtained properties (i.e. specific surface , antibacterial activity) for some sample of materials are relevant for the application in water purification process, the tests on the water samples are not included.
- In this context I suggest to modify the title of manuscript as: Zinc-silver doped mesoporous hydroxyapatite synthesized via ultrasonic in combination with sol-gel method with increased bacterial activity and in the conclusions section, as it is already mentioned, to be emphasized the potential application area of these materials (i.e. water purification)
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 1 comments
Thank you very much for your valuable suggestion. Here we provide a point-by point response to your comments.
The paper aims to develop a HA material doped with Zn-Ag using the ultrasonic assisted sol-gel technique. The obtained results are relevant for to predict the application area of these materials. The paper is well structured with appropriate content and references.
There are few comments:
- In the title is mentioned that the synthesized materials are appropriate for
“increased bacterial activity in water purification”
Answer: We have modified the title to “Zinc-silver doped mesoporous hydroxyapatite synthesized via ultrasonic in combination with sol-gel method for increased anti-bacterial activity in water purification”. Thus, we have revised the title accordingly.
- Although the obtained properties (i.e. specific surface, antibacterial activity) for some
sample of materials are relevant for the application in water purification process, the tests on the water samples are not included.
Answer: This manuscript displays preliminary results that focuses on physicochemical properties and antibacterial activity of Zn-Ag doped HA. Please note that water purification in this paper focuses on the aspect of the removal of biological contaminants in water bodies and wastewater, hence, the anti-bacterial activity was examined. Other contaminants removed under water purification will be part of our further studies.
- In this context I suggest to modify the title of manuscript as: Zinc-silver doped mesoporoushydroxyapatite synthesized via ultrasonic in combination with sol-gel method with increasedbacterial activity and in the conclusions section, as it is already mentioned, to beemphasized the potential application area of these materials (i.e. water purification)
Answer: The title of this manuscript has been revised to “Zinc-silver doped mesoporous hydroxyapatite synthesized via ultrasonic in combination with sol-gel method for increased anti-bacterial activity” as per suggestion of the reviewer.
We also attached a PDF file of our response to your comments. Please see the attachment
Author Response File: Author Response.pdf
Reviewer 2 Report
The manuscript is well-written and carries scientific significance in the field of sustainability. The study aimed to synthesize mesoporous zinc and silver-doped hydroxyapatite nanoparticles via the sol-gel method assisted by ultrasonic radiations. The materials were calcined at two different calcination temperatures for different time intervals. The prepared materials were successfully characterized by XRD, FTIR, BET, and TEM analysis. Finally, the antibacterial activity was established using five different bacteria following qualitative standard test protocols.
In general, I recommend the manuscript for further consideration to be published in Sustainability but I still carry some questions to be answered by the authors with reference to recent novelties in the area of research.
1. Why the authors use two different calcination temperatures (600 C and 1100 C) and time intervals (1 hr and 4 hrs)?
2. Regarding your XRD patterns, What do (*) and (o) signify in your measurements?
3. You need EDX measurements for the better characterization of elemental analysis of your prepared materials.
4. On what basis you state that your material is adsorbent material?
5. You can add at least one quantitative antibacterial evaluation for all the prepared samples, if possible.
Overall, the manuscript needs major revisions to be considered further.
Author Response
Response to Reviewer 2 comments
Thank you very much for your valuable suggestion. Here we provide a point-by point response to your comments. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
I have two recommendations.
Add information in the introduction about the application of this material (Zinc-silver doped mesoporous hydroxyapatite) for water purification.
Other studies are cited in the results, however, it is recommendable to compare the results with other studies to highlight the advantages of Zinc-silver doped mesoporous hydroxyapatite with other materials.
Comments for author File: Comments.pdf
Author Response
Response to Reviewer 3 comments
Thank you very much for your valuable suggestion. Here we provide a point-by point response to your comments.
I have carefully read the manuscript. In my opinion, the research may be interesting for readers, however it needs some minor changes before publication. I have two recommendations. Add information in the introduction about the application of this material (Zinc-silver doped mesoporous hydroxyapatite) for water purification. Other studies are cited in the results; however, it is recommendable to compare the results with other studies to highlight the advantages of Zinc-silver doped mesoporous hydroxyapatite with other materials.
Answer: Review of related literature such as the application of HA and metallic doped HA particles for water purification has already mentioned in the Introduction, pg. 2, lines 83-91. Water contaminants like dyes, Fe(II) and Al(III) have been removed using Ag-doped HA, Hydroxyapatite combined with copper and ferrite, Fe-substituted HA and Co-substituted HA. However, the specific material in the present work, which is Zn-Ag doped HA, synthesized via sol-gel method combined with ultrasonic irradiation for water purification application (anti-bacterial activity) has never been investigated.
We also attached a PDF file of our response. Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Some answers of the authors seem to be satisfactory. However, the authors didn't examine the adsorption property of their synthesized material and thus the statement "a suitable adsorbent material" in the abstract part is not supported. A similar statement "a promising adsorbent material in water purification" in the conclusion part also needs modification. It is not only the surface area that plays a major role in the adsorption of the contaminants rather there are several other too.
I would also clarify here that, in quantitative antibacterial assessment the number of bacterial colonies is measured and compared with the control. Thus, as a result, you can get a percent antibacterial activity of the material.
Your antibacterial measurement is a qualitative method where you measured the zone of inhibition in agar plate.
Author Response
Responses to reviewer:
- Some answers of the authors seem to be satisfactory. However, the authors didn't examine the adsorption property of their synthesized material and thus the statement "a suitable adsorbent material" in the abstract part is not supported. A similar statement "a promising adsorbent material in water purification" in the conclusion part also needs modification. It is not only the surface area that plays a major role in the adsorption of the contaminants rather there are several other too.
Answer: Thank you for your valuable suggestion and comment. The authors agree with the reviewer that adsorption property of the synthesized material has not yet been examined. So, we have removed the word “adsorbent” from the sentence in both Abstract and Conclusion as follows:
Abstract (pg. 1, line 41)
The original sentence: “This material showed inhibition zones ranging from 7-11 mm, implying that it is a suitable adsorbent material with an antibacterial action for environmental applications specifically for water purification”.
The revised sentence: “This material showed inhibition zones ranging from 7-11 mm, implying that it is a suitable material with an antibacterial action for environmental applications specifically for water purification”.
Conclusion (pg. 14, line 337-338)
The original sentence: “Hence, Zn0.75Ag0.25 doped HA1100 displayed excellent anti-bacterial property, which makes it a promising adsorbent material in water purification”.
The revised sentence: “Hence, Zn0.75Ag0.25 doped HA1100 displayed excellent anti-bacterial property, which makes it a promising material in water purification”.
- I would also clarify here that, in quantitative antibacterial assessment the number of bacterial colonies is measured and compared with the control. Thus, as a result, you can get a percent antibacterial activity of the material.
Your antibacterial measurement is a qualitative method where you measured the zone of inhibition in agar plate.
Answer: Thanks for the comment! The antibacterial activity of the synthesized material in our study is examined via their clear zone, MIC and MBC values that is classified as a qualitative method as the reviewer suggested. For the quantitative method of antibacterial activity, this would be part of our further studies.
Author Response File: 
Author Response.docx
