Magnetic Iron Nanoparticles: Synthesis, Surface Enhancements, and Biological Challenges

Round 1

Reviewer 1 Report

The review articles “Magnetic nanoparticles: Synthesis, surface enhancements, and toxicological concerns”, the author focuses “on the role of magnetic nanoparticles (MNPs), their physicochemical properties, their potential applications, and their association with the consequent toxicological effects in complex biologic systems” focus on the role of magnetic nanoparticles (MNPs), their physicochemical properties, their potential applications, and their association with the consequent toxicological effects in complex biologic systems.

 

            In the Introduction part the authors emphasize the correlation between particle morphology and structure and their physicochemical properties, comparing their size with the entire spectrum of cells in the human body and also how their toxicology changes with nano structuring.

            The authors exemplify one of the most significant applications of nanoparticles in medical diagnostics as contrast agents for MRI and make a classification of their specific characteristics. The working mechanism as contrast agents of complexes of lanthanide elements like gadolinium or transition metal as manganese was has been briefly presented. At this point, the particular case of magnetic nanoparticles were introduced and exemplified in one sentence and in a form of a drawing the biomedical fields in which magnetic nanoparticles find their use.

                Personally, I think at this point it is important to describe the limitations of existing materials, especially in terms of their toxicity, and highlight the advantages that magnetic nanoparticles would have over conventional ones.

 

                The most suitable MNPs are magnetite and maghemite and the author consider that “the full impact of the nanoparticles in general and in the case of magnetic materials is yet to be fully understood”. The authors present a brief literature review on the toxicological impact of these particles on cell lines, in the bibliographies between 54-68. The as presented references are relatively new and present in general the potential toxicity of iron oxide magnetic nanoparticles.

 

            Why the authors believe that there is no comprehensive image of the toxicological impact of magnetic nanoparticles on biological cells. The literature is full of articles and reviews discussing toxicology aspects of MNPS systems used in biomedical applications.

 

What are the limitations of the analytical methods presented in these articles?

 

At the beginning of second chapter, Magnetic nanoparticle synthesis methods, the authors list and exemplify through a figure, the synthesis methods existing in the literature for the synthesis of magnetic nanoparticles, also mentioning their applications in various fields, not strictly related to the biomedical area.

 

            Personally, I believe that given the purpose of this article, which is a review of the synthesis and possible toxic effects of MNPs on human cells, the applications strictly in the biomedical area should be particularized and entered in detail in this aria.

            The drawing in Figure 3 shows the industrial applications of magnetic nanoparticles, which is not very relevant to the proposed topic.

            Table 1 presents in a very efficient and well-organized way the synthesis methods of magnetic nanoparticles. Subsequently, each of the synthesis methods exemplified in the table is described in detail, by mentioning some bibliographic sources (5-6) and briefly mentioning the advantages and disadvantages of the method.

           

            The organization of this chapter is not done properly.

            Subchapter 2.1 Aqueous methods should strictly contain methods that take place in water. 2.1.2.Thermal decomposition method, is not an aqueous method, also the authors say “Thermal decomposition of organo-metallic precursor compounds in organic solvents with high boiling points”. Please reorganize.

            A suggestive drawing of 2.1.5. Microemulsion synthesis method is shown in Figure 4. Is this drawing original, made by the authors?

 

In order to follow the classification made in Table 1, I personally consider that the methods exemplified as 2.1.6. Sonochemically assisted and 2.1.7. Microwave-assisted should be included in subchapter 2.2 Assisted routs and 2.2. Biological synthesis routes will become 2.3.

Subchapter 2.3. Surface Coating has been introduced, which would become 2.4.               I consider a short introduction here is necessary to emphasize the necessity of surface coverage of magnetic nanoparticles.

Except for the coprecipitation method, each of the listed methods provides MNPs already coated with some layers. Subsequent coatings may be necessary from the point of view of surface biocompatibility. A discussion is needed here.

 

In Chapter 3. Toxicological concerns, authors presents different toxicological assays in MNPs, well-structured in Table 2. What I think is missing from this table in the right of each reference, should have been mentioned the MNPs type and the shell of the particles, because the coating plays a particularly important role in the toxicology problem. In this way there is an overview of the types of MNPs and coatings that are the least toxic in biomedical applications.

            The most important methods for determining the toxicity of MNP samples are described below: in vitro, ex vivo, and in vivo. Each of these methods has been briefly described highlighting their advantages and disadvantages. Given that this article is a review of the toxicity of MNPs, I expected to see examples of a number of measurements by researchers in the field, with various results. There are no examples and articles cited at all.

            In Chapter 4. Regulation and control the author describe some regulation proposals that different organizations have made and claim that “even though research and toxicity approaches have been made to identify the potential toxicity of MNPs, there are no clear regulatory parameters to control these materials' production, interaction, and disposal”. Is this true?

           

            The Conclusions part is inconclusive, not correlate with the purpose of the article to closely follow the synthesis correlated with the toxicology of the samples thus prepared.

 

Author Response

Reviewer # 1

 

The review article “Magnetic nanoparticles: Synthesis, surface enhancements, and toxicological concerns”, the author focuses on the role of magnetic nanoparticles (MNPs), their physicochemical properties, their potential applications, and their association with the consequent toxicological effects in complex biologic systems.

 

• In the Introduction part the authors emphasize the correlation between particle morphology and structure and their physicochemical properties, comparing their size with the entire spectrum of cells in the human body and also, how their toxicology changes with nano structuring.

 

The authors exemplify one of the most significant applications of nanoparticles in medical diagnostics as contrast agents for MRI and make a classification of their specific characteristics. The working mechanism as contrast agents of complexes of lanthanide elements like gadolinium or transition metal as manganese had been briefly presented. At this point, the particular case of magnetic nanoparticles was introduced and exemplified in one sentence and in a form of a drawing the biomedical fields in which magnetic nanoparticles find their use.

 

Personally, I think at this point it is important to describe the limitations of existing materials, especially in terms of their toxicity, and highlight the advantages that magnetic nanoparticles would have over conventional ones.

 

 R: Thank you for your comments and recommendations. We have made the proper changes in the introduction section.

 

• The most suitable MNPs are magnetite and maghemite and the author consider that “the full impact of the nanoparticles in general and in the case of magnetic materials is yet to be fully understood”. The authors present a brief literature review on the toxicological impact of these particles on cell lines, in the bibliographies between 54-68. The as presented references are relatively new and present in general the potential toxicity of iron oxide magnetic nanoparticles.

 

Why the authors believe that there is no comprehensive image of the toxicological impact of magnetic nanoparticles on biological cells. The literature is full of articles and reviews discussing toxicology aspects of MNPS systems used in biomedical applications.

 

What are the limitations of the analytical methods presented in these articles?

 

R: We appreciate your comment. The proper changes have been added in lines 82 – 87.

 

• At the beginning of second chapter, Magnetic nanoparticle synthesis methods, the authors list and exemplify through a figure, the synthesis methods existing in the literature for the synthesis of magnetic nanoparticles, also mentioning their applications in various fields, not strictly related to the biomedical area.

 

Personally, I believe that given the purpose of this article, which is a review of the synthesis and possible toxic effects of MNPs on human cells, the applications strictly in the biomedical area should be particularized and entered in detail in this area.

 

R: Thank you for your remark; the proper changes have been made in lines 130-135.

 

• The drawing in Figure 3 shows the industrial applications of magnetic nanoparticles, which is not very relevant to the proposed topic.

 

R: We appreciate the observation. Changes have been made in Fig. 3.

 

• Table 1 presents in a very efficient and well-organized way the synthesis methods of magnetic nanoparticles. Subsequently, each of the synthesis methods exemplified in the table is described in detail, by mentioning some bibliographic sources (5-6) and briefly mentioning the advantages and disadvantages of the method.

The organization of this chapter is not done properly.

Subchapter 2.1 Aqueous methods should strictly contain methods that take place in water. 2.1.2. Thermal decomposition method is not an aqueous method, also the authors say “Thermal decomposition of organo-metallic precursor compounds in organic solvents with high boiling points”. Please reorganize.

 

R: Thank you for your comment. The reorganization of the section was done.

 

• A suggestive drawing of 2.1.5. Microemulsion synthesis method is shown in Figure 4. Is this drawing original, made by the authors?

 

R: The drawing was inspired by literature but is an original interpretation by the authors. We appreciate the observation.

 

• In order to follow the classification made in Table 1, I personally consider that the methods exemplified as 2.1.6. Sonochemically assisted and 2.1.7. Microwave-assisted should be included in subchapter 2.2 Assisted routs and 2.2. Biological synthesis routes will become 2.3.

 

R: We appreciate the observation. Changes in section numbering and organization have been made in the revised version of the MS.

 

• Subchapter 2.3. Surface Coating has been introduced, which would become 2.4. I consider a short introduction here is necessary to emphasize the necessity of surface coverage of magnetic nanoparticles.

 

Except for the coprecipitation method, each of the listed methods provides MNPs already coated with some layers. Subsequent coatings may be necessary from the point of view of surface biocompatibility. A discussion is needed here.

 

R: Thank you for the recommendation. Changes were made in lines 338-342 and 352-355.

 

• In Chapter 3. Toxicological concerns, authors present different toxicological assays in MNPs, well-structured in Table 2. What I think is missing from this table in the right of each reference, should have been mentioned the MNPs type and the shell of the particles, because the coating plays a particularly important role in the toxicology problem. In this way there is an overview of the types of MNPs and coatings that are the least toxic in biomedical applications.

 

R: Thank you for the remark. Changes have been made in lines 338-342, 352-355, and Table 2.

 

• The most important methods for determining the toxicity of MNP samples are described below: in vitro, ex vivo, and in vivo. Each of these methods has been briefly described highlighting their advantages and disadvantages. Given that this article is a review of the toxicity of MNPs, I expected to see examples of a number of measurements by researchers in the field, with various results. There are no examples and articles cited at all.

 

R: We have added Table 3 in the revised version of the MS. We thank you for the comment.

 

• In Chapter 4. Regulation and control the author describe some regulation proposals that different organizations have made and claim that “even though research and toxicity approaches have been made to identify the potential toxicity of MNPs, there are no clear regulatory parameters to control these materials' production, interaction, and disposal”. Is this true?

   

R: Thank you for your comment. Since 2011 several world organizations have discussed the possible regulations on nanomaterials. However, many of the regulations considered nanomaterials as their bulk counterparts or had no restrictions. Still, studies on the subject suggest that there are evident differences and must be regulated accordingly. We consider that the term “regulatory parameters” should be clarified to be aware that the NMs and bulk materials behave differently.

      

• The Conclusions part is inconclusive, not correlate with the purpose of the article to closely follow the synthesis correlated with the toxicology of the samples thus prepared.

 

R: Thank you for the observation. The proper changes have been made in lines 645-666.

Reviewer 2 Report

This paper reports on the Magnetic nanoparticles: Synthesis, surface enhancements, and 2 toxicological concerns. The English language needs to be thoroughly reviewed throughout the paper. The article is incomplete in parts, with some explanations and clarifications needed for better understanding. I do recommend that this article be published in Journal of Processes after Major revision.

 

1)      The English writing in the paper also needs to be improved as there are many grammatical errors and incomplete sentences throughout the paper that made it difficult to read.

2)      In the abstract section, the main findings of the research should be written numerically and quantitatively.

3)      At the end of the abstract, write a general conclusion.

4)      In the introduction and discussion sections, use the content of the following articles and refer to them in the references section: 0.1016/j.jece.2021.105889; 10.1080/01932691.2021.1947847; 10.1007/s13399-021-01668-7

5)      In the introduction section, a number of similar studies should be mentioned.

6)      In the methods section, the inclusion and exclusion criteria from study should be written.

7)      The entire text of the article should be written according to the journal format (introduction, methods, results, discussion and conclusion).

8)      In the methods section, how many articles were reviewed and what was the criteria for inclusion and exclusion from the study?

9)      Research innovation should be written.

10)  In the Methods, the type of study to be written.

11)  The discussion section of the article is poorly written. Must be upgraded with new articles.

12)  The strengths and weaknesses of this study compared to other studies should be written.

 

Author Response

Reviewer # 2

 

This paper reports on the Magnetic nanoparticles: Synthesis, surface enhancements, and toxicological concerns. The English language needs to be thoroughly reviewed throughout the paper. The article is incomplete in parts, with some explanations and clarifications needed for better understanding. I do recommend that this article be published in Journal of Processes after Major revision.

 

• The English writing in the paper also needs to be improved as there are many grammatical errors and incomplete sentences throughout the paper that made it difficult to read.

 

R: We appreciate the recommendation and have made several changes throughout the MS's revised version to improve the language's quality.

 

• In the abstract section, the main findings of the research should be written numerically and quantitatively.

 

R: Thank you for the remark. The abstract has been improved in the revised version of the MS.

 

• At the end of the abstract, write a general conclusion.

 

R: Thank you, the abstract has been improved in the revised version of the MS (lines 26-32).

 

• In the introduction and discussion sections, use the content of the following articles and refer to them in the references section: 10.1016/j.jece.2021.105889; 10.1080/01932691.2021.1947847; 10.1007/s13399-021-01668-7

 

R: We thank you for the comment. The relevant information was added in line 131 (references 71-73).

 

• In the introduction section, a number of similar studies should be mentioned.

 

R: We appreciate the suggestion. Following the author´s guide for the “Review paper”, similar studies and comparisons between them are presented in the following sections (2-4) in the revised version of the MS.

 

• In the methods section, the inclusion and exclusion criteria from study should be written.

 

R: Thank you for your comment. Following the author´s guide for the “Review paper”, the revised version of the MS does not include a methodology section. Nevertheless, we had included a paragraph indicating the main porpoise of the MS (lines 114-123).

 

• The entire text of the article should be written according to the journal format (introduction, methods, results, discussion, and conclusion).

 

R:  We appreciate the observations regarding this matter. Nevertheless, we considered that the way the revised version of the MS is presented has an adequate structure to display the information for better understanding.

 

• In the methods section, how many articles were reviewed and what was the criteria for inclusion and exclusion from the study?

 

R: Thanks for the comment. The information has been added in lines 114-123.

 

• Research innovation should be written.

 

R: The proper modification has been done in lines 114-123.

 

• In the Methods, the type of study to be written.

 

R: The proper modification has been done in lines 114-123.

 

• The discussion section of the article is poorly written. Must be upgraded with new articles.

 

R: Thank you for the comment. New articles were added throughout the revised version of the MS.

 

• The strengths and weaknesses of this study compared to other studies should be written.

 

R: We appreciate the observation. The proper modification has been done in lines 114-123.

Reviewer 3 Report

The study is really interesting and the reviewer believes that the manuscript can be published in this journal. 

I suggest to include SEM imagens of magnetic nanoparticles and if possible to show he structure of these particles inside the particles in order to see the density of the particles and also analyse if this particle is a structure of closed cells or open cells.

These particles are used for coating and reinforcement of polymers, I suggest to include information about the adhesion of these particles to polymers. The level of adhesion to different materials.

Author Response

Reviewer # 3

 

The study is really interesting, and the reviewer believes that the manuscript can be published in this journal.

 

• I suggest to include SEM imagens of magnetic nanoparticles and if possible to show the structure of these particles inside the particles in order to see the density of the particles and also analyze if this particle is a structure of closed cells or open cells.

 

R: Thank you for the suggestion. An illustrative diagram can be seen in the revised version of the MS in Fig. 3, depicting the different shapes of the materials and a representative TEM image.

 

• These particles are used for coating and reinforcement of polymers, I suggest to include information about the adhesion of these particles to polymers. The level of adhesion to different materials.

 

R: Thank you for your comment. Information was added in lines 422-427.

Reviewer 4 Report

In this Review paper, synthesis methods, surface treatment and toxicology issues of magnetic nanoparticles are reviewed. The authors did a good effort, and some corrections are needed to make this better than it is now. First of all, if you analyze only iron oxide nanoparticles, and not cobalt or nickel (which are also magnetic), why don’t you specify this in the title of your manuscript?

More comments are below:

The introduction seems to contain more than 1000 words. This is not needed. Something like 800-900 words would be more than sufficient.

Try not to make too sudden or too fast transitions in your text. Already in the first paragraph of the Introduction you speak about NPs, a bit about magnetism, then about the human body and about the sizes of the cells. Better try to write a more smooth text, with slower transitions between different things.

Page 2, line number 52: Heating efficiency is sometimes increased a lot when using anisotropic morphologies of iron oxide NPs, such as flower-like structures, instead of spherical particles. Please see and site: ACS Appl. Mater. Interfaces Vol 13, page 45870 (2021).

Line 49: ‘single dominion’ or ‘single domain’?

Line 56: why is ZnO there? The review is mostly about magnetic NPs, isn’t it?

Lines 57-60: Not so clear: If you increase the particle size, the number of atoms on the surface will be reduced. So in the first part you write ‘can be toxic’ while in the last part you write ‘thus reducing the harmful effects’? This is not so clear, the whole phrase I mean. Not coherent, not concise. The two parts of the whole phrase seem a bit contradictory to each other.

At line 53-54 and at line 64 you write the same thing: that NPs generate agglomerates to reduce their energy. Please, avoid repetitions, especially within such a short space of lines!

Figure 1 does not look so nice. Fuzzy shapes, unclear and dark letter fonts on a dark grey background and so on. Improve it, please.

Line 107: Which magnetic characteristics and which size range? Please be clear! The word ‘significant’ means nothing, when used alone.

Figure 2, on the top: It is not correct to write ‘aqueous route’. When you use thermal decomposition synthesis up to 300 C of temperature, you need an organic solvent, and not water. I would change it to ‘colloidal routes’, or ‘wet-chemical routes’. Figure 2 bottom-left: Change ‘sonochemestry’ to ‘sonochemistry’.

Section 2 is supposed to describe synthesis methods. You have a figure there, Figure 2, and under the Figure you write about properties and applications! Go 'directly' to the synthesis methods, instead. This section’s title is about synthesis, not about applications! Have a better order in your writing. OK, then you continue writing about some synthesis methods, later, but as I wrote above, please keep a better order in your text and remove redundant content.

Line 153: Iron oxide magnetic NPs can be also used in sensing applications. You can see and cite: Electrochim. Acta, Vol 360, Page 136981 (2020)

Figure 3: Does the black circle in the middle look nice, what do you think? I don’t understand its use there. At the top-left part of the Figure, correct ‘vacumm’ to ‘vacuum’.

Line 181: Is it common to use an inert gas atmosphere during the water-based coprecipitation synthesis? I don’t think so. For example, the reference 122 that you cite, speaks about any such gas atmosphere?

Line 194: A typical example for additives (surfactants) used in thermal decomposition synthesis is the oleic acid-oleylamine ligand pair. Please see and cite: Nanoscale Horiz. Vol 7, Page 941 (2022) (- you mention oleic acid also at line 299). For a general review on ligands in nanoparticle synthesis, see also: Chem. Rev. 119, 4819 (2019).

In general, try to write more insights in your manuscript. Do not just ‘mention’ things but try to show what we learn from those different synthetic techniques, what insights we gain.

Line 196: It is not aqueous medium, they are organic solvents!

Line 233: You write ‘due to’ twice in the same line. Don’t do that. Replace one by ‘thanks to’ or ‘because of’.

Line 285: For bacteria used as reducing agents for nanoparticle synthesis, you can see and cite this chapter:

https://pubs.rsc.org/en/content/chapter/9781839163623-00316/978-1-83916-362-3

Line 300: For the roles of PVP in (magnetic) nanoparticle synthesis see also: Dalton Trans. 44, 17883 (2015).

Line 337: For silica-coated magnetic NPs as well as other magnetic nanocomposites (e.g. carbon-coated, metal-coated), you can see their synthesis, properties, advantages, applications and cite this Review: Adv. Sci. Vol 8, 2004951 (2021).

Figure 5 at page 13: You write at the caption ’75 nm’ but at the Figure image it is 70 nm. Check and correct.

Line 450: Be careful, please. Probably you mean ‘in vitro’ there, and not ‘in vivo’.

Table 3 seems to have the same title with Table 2. Something wrong is there.

Line 497: How in practice can you separate an organ from general circulation? The heart is always working and sends blood everywhere, doesn’t it?

Line 594: For the fate of magnetic NPs in the environment, for example after their use in water treatment, see also: Environ. Sci.: Water Res. Technol. Vol 2, Page 43 (2016).

References list:

Ref 65 is the same with Ref 248. So delete the Ref 248 and re-arrange the numbering of references in both main manuscript and list of references.

Ref 111 is the same with Ref 142. Remove the ref 142, please.

Ref 138: The author is not named ‘A. Review’. Correct it.

Ref 215 is the same with Ref 216. Remove the 216, please.

Ref 268: Write it better please. C. Environmental and P. Act seem like author names in the way they are written! They are not authors! Check and correct.

Author Response

Reviewer # 4

 

In this Review paper, synthesis methods, surface treatment and toxicology issues of magnetic nanoparticles are reviewed. The authors did a good effort, and some corrections are needed to make this better than it is now. First of all, if you analyze only iron oxide nanoparticles, and not cobalt or nickel (which are also magnetic), why don’t you specify this in the title of your manuscript? More comments are below:

 

R: We appreciate the observation. The proper changes have been added in the revised version of the MS, along with the appropriate modification in the MS title.

 

• The introduction seems to contain more than 1000 words. This is not needed. Something like 800-900 words would be more than sufficient.

 

R: Thank you for the comment. We narrowed the information to 1000 words trying to fulfill all the reviewers’ requests.

 

• Try not to make too sudden or too fast transitions in your text. Already in the first paragraph of the Introduction you speak about NPs, a bit about magnetism, then about the human body and about the sizes of the cells. Better try to write a more smooth text, with slower transitions between different things.

 

R: Thank you for the suggestion. Changes were made throughout the text to a better connection between sections.

 

• Page 2, line number 52: Heating efficiency is sometimes increased a lot when using anisotropic morphologies of iron oxide NPs, such as flower-like structures, instead of spherical particles. Please see and site: ACS Appl. Mater. Interfaces Vol 13, page 45870 (2021).

 

R: Thank you for the observation. The information was added in lines 49-51 (Ref. 14).

 

• Line 49: ‘single dominion’ or ‘single domain’?

 

R: Thank you for your correction. The mistake was mended in line 45.

 

• Line 56: why is ZnO there? The review is mostly about magnetic NPs, isn’t it?

 

R: We appreciate the observation. The information has been corrected in lines 51-54.

 

• Lines 57-60: Not so clear: If you increase the particle size, the number of atoms on the surface will be reduced. So, in the first part you write ‘can be toxic’ while in the last part you write ‘thus reducing the harmful effects’? This is not so clear, the whole phrase I mean. Not coherent, not concise. The two parts of the whole phrase seem a bit contradictory to each other.

 

R: Thank you for the remark. The idea was rephrased and corrected in lines 59-66.

 

• At line 53-54 and at line 64 you write the same thing: that NPs generate agglomerates to reduce their energy. Please, avoid repetitions, especially within such a short space of lines!

 

R:  Thank you for the observation. The integration of the information was made in lines 59-66.

 

• Figure 1 does not look so nice. Fuzzy shapes, unclear and dark letter fonts on a dark grey background and so on. Improve it, please.

 

R: Fig. 1 has been changed in the revised version of the MS. We appreciate the observation.

 

• Line 107: Which magnetic characteristics and which size range? Please be clear! The word ‘significant’ means nothing, when used alone.

 

R: We appreciate the observation. Additional information was added in lines 94-96.

 

• Figure 2, on the top: It is not correct to write ‘aqueous route’. When you use thermal decomposition synthesis up to 300 C of temperature, you need an organic solvent, and not water. I would change it to ‘colloidal routes’, or ‘wet-chemical routes’. Figure 2 bottom-left: Change ‘sonochemestry’ to ‘sonochemistry’.

 

R: Thank you for your comment. Changes were made in Fig. 2 in the revised version of the MS.

 

• Section 2 is supposed to describe synthesis methods. You have a figure there, Figure 2, and under the Figure you write about properties and applications! Go 'directly' to the synthesis methods, instead. This section’s title is about synthesis, not about applications! Have a better order in your writing. OK, then you continue writing about some synthesis methods, later, but as I wrote above, please keep a better order in your text and remove redundant content.

 

R: Changes were made in lines 130-135 for a better transition along the information. We appreciate the observation.

 

• Line 153: Iron oxide magnetic NPs can be also used in sensing applications. You can see and cite: Electrochim. Acta, Vol 360, Page 136981 (2020)

 

R: We appreciate the suggestion. The reference was added in line 129 (Ref. 66).

 

• Figure 3: Does the black circle in the middle look nice, what do you think? I don’t understand its use there. At the top-left part of the Figure, correct ‘vacumm’ to ‘vacuum’.

 

R: Thank you for your observation. Figure 3 was modified in the revised version of the MS.

 

• Line 181: Is it common to use an inert gas atmosphere during the water-based coprecipitation synthesis? I don’t think so. For example, the reference 122 that you cite, speaks about any such gas atmosphere?

 

R: We thank you for the observation. The proper changes were made in lines 174-176.

 

• Line 194: A typical example for additives (surfactants) used in thermal decomposition synthesis is the oleic acid-oleylamine ligand pair. Please see and cite: Nanoscale Horiz. Vol 7, Page 941 (2022) (- you mention oleic acid also at line 299). For a general review on ligands in nanoparticle synthesis, see also: Chem. Rev. 119, 4819 (2019).

 

R: We appreciate the suggestion. The information has been added in lines 192-195 (Ref. 123).

 

• In general, try to write more insights in your manuscript. Do not just ‘mention’ things but try to show what we learn from those different synthetic techniques, what insights we gain.

 

R: The proper changes have been marked throughout section 2 in the revised version of the MS.

 

• Line 196: It is not aqueous medium, they are organic solvents!

 

R: The proper modification has been made in lines 186-187.

 

• Line 233: You write ‘due to’ twice in the same line. Don’t do that. Replace one by ‘thanks to’ or ‘because of’.

 

R: Thank you for the correction. The change has been made in line 237 in the revised version of the MS.

 

• Line 285: For bacteria used as reducing agents for nanoparticle synthesis, you can see and cite this chapter:

https://pubs.rsc.org/en/content/chapter/9781839163623-00316/978-1-83916-362-3

 

R: Thank you for your suggestion. The reference was added in line 300 along with the existing ones (Ref. 149).

 

• Line 300: For the roles of PVP in (magnetic) nanoparticle synthesis see also: Dalton Trans. 44, 17883 (2015).

 

R: Thank you for the suggestion. The reference was added in line 315 (Ref. 154).

 

• Line 337: For silica-coated magnetic NPs as well as other magnetic nanocomposites (e.g. carbon-coated, metal-coated), you can see their synthesis, properties, advantages, applications and cite this Review: Adv. Sci. Vol 8, 2004951 (2021).

 

R: Thank you for your suggestion. The reference was added in line 354 (Ref. 175).

 

• Figure 5 at page 13: You write at the caption ’75 nm’ but at the Figure image it is 70 nm. Check and correct.

 

R: The modification has been done in Fig. 5 caption. We appreciate the observation.

 

• Line 450: Be careful, please. Probably you mean ‘in vitro’ there, and not ‘in vivo’.

 

R: We appreciate the remark. The proper modifications were done in lines 487-492 in the revised version of the MS.

 

• Table 3 seems to have the same title with Table 2. Something wrong is there.

 

R: Thank you for your correction; it has been changed.

 

• Line 497: How in practice can you separate an organ from general circulation? The heart is always working and sends blood everywhere, doesn’t it?

 

R: According to your observation, it is correct. And to clarify how the ex vivo analysis is carried out, additional information was added in lines 499-504.

 

• Line 594: For the fate of magnetic NPs in the environment, for example after their use in water treatment, see also: Environ. Sci.: Water Res. Technol. Vol 2, Page 43 (2016).

 

R: Thank you for the suggestion. The reference was added in line 643 (Ref. 286).

 

• References list:

 

Ref 65 is the same with Ref 248. So delete the Ref 248 and re-arrange the numbering of references in both main manuscript and list of references. (59)

 

Ref 111 is the same with Ref 142. Remove the ref 142, please. (109)

 

Ref 138: The author is not named ‘A. Review’. Correct it. (137)

 

Ref 215 is the same with Ref 216. Remove the 216, please. (221)

 

Ref 268: Write it better please. C. Environmental and P. Act seem like author names in the way they are written! They are not authors! Check and correct. (278)

 

R: Thank you for the observations. Changes were made and marked in the revised version of the MS reference section.

 

Round 2

Reviewer 2 Report

Accepted.

Author Response

We appreciate the time invested in this reviewer process to improve our work. Thank you.