Simple Spin-Coating Preparation of Hydrogel and Nanoparticle-Loaded Hydrogel Thin Films

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The work on the simple preparation of thin films of hydrogels and nanoparticle-loaded hydrogels using the spin-coating technique, using alginate gelation with a calcium salt and loaded with silver nanoparticles. Despite the variety of work in this field, the authors are seeking a suitable way to obtain these materials. However, the manuscript requires a series of essential characterizations in the area of ​​materials production, and it is not clear what the application of the obtained material would be for it to be accepted. My revisions are listed below.
1. There is no characterization of the polymer matrix, such as the mannurate:gluconate ratio of the polymer, FTIR characterization, and NMR.
2. What is the molecular weight of the polymer used? 3. Characterization analyses are missing, such as thermogravimetry, which is essential for these materials.
4. FTIR characterization is missing.
5. The size of the silver particles obtained is not mentioned.
6. How do the mechanical properties of the obtained material vary?
7. If they are hydrogel films, how do they characterize the hydrogels? Water absorption capacity is missing, or contact angle tests are not performed.
8. Figure 2 is not clear. It needs to be improved for better understanding.
9. Further discussion is missing in the results and discussion section, but this is related to the poor characterization of the obtained materials.

Author Response

The work on the simple preparation of thin films of hydrogels and nanoparticle-loaded hydrogels using the spin-coating technique, using alginate gelation with a calcium salt and loaded with silver nanoparticles. Despite the variety of work in this field, the authors are seeking a suitable way to obtain these materials.

 

Dear reviewer, thank you very much for your observations, very precise and useful. We think that you have identified the weaknesses of our work and this has allowed us to try to correct them. Here you can find our answers to your points that we hope will be convincing.

 

However, the manuscript requires a series of essential characterizations in the area of materials production, and it is not clear what the application of the obtained material would be for it to be accepted.

As for applications, it is difficult to answer precisely, also because it was not our main goal to identify and test real applications of our samples. What we can say is that alginate-based hydrogels, and in particular those loaded with nanoparticles, have numerous applications in the biomedical field, particularly in wound healing, drug delivery, and tissue engineering. In addition, hydrogels in film form can exhibit the same properties as in bulk form, but also exhibit faster response speed and excellent ability to adapt appropriately to external environments and situations, great ability to integrate with other components and materials. Silver particles are well known for their excellent bactericidal and antibiotic properties and there is a vast literature on the subject. It is easy to imagine that these properties are preserved even when they are embedded in thin films of hydrogels. We therefore think that calcium alginate thin films prepared in this way, that is with a simple, rapid and inexpensive technique, can certainly be applied in this sector and this is our final goal. However, a rigorous demonstration of these capabilities is very complex, requires in-depth studies, it would also be necessary to verify the effects of different parameters, such as the concentration of nanoparticles or the rigidity of the film, its ability to allow gas exchanges and so on. Our primary goal was rather to show the possibility of obtaining materials with an innovative method. the study of real applications is absolutely important, but deserves dedicated research.

 

My revisions are listed below.

1. There is no characterization of the polymer matrix, such as the mannurate:gluconate ratio of the polymer, FTIR characterization, and NMR.

We agree with the reviewer that a characterization of the polymer matrix is very important. It is also true that the scientific literature is very consistent that alginate gels form very easily and very quickly when solutions of divalent cations (calcium as in this case) and sodium alginate come into contact. Therefore it would be surprising if this case was an exception. We have in any case, following your request, characterized our samples by FTIR spectroscopy and modified the manuscript text to describe the results thus obtained and added a figure to show the spectra. In general, they are in good agreement with the data reported in the literature, indicating that the gel matrix is indeed constituted by calcium alginate. The sodium alginate we used is a commercial product and often information about the ratio of the units constituting the chains is not available. However, it is possible to estimate this ratio from the absorbance of two specific bands, allowing for quantification of their relative proportions. In particular, the band at about 1030 cm⁻¹ is associated with the O-H bending vibration in mannuronate (M) units, while the band at 1080 cm⁻¹ is associated with the C-O-C stretching vibration in guluronate (G) units. From their ratio, at least an indicative estimate of the composition can be made. Having measured the spectra, we also evaluated the ratio of the monomeric units

On the contrary, although NMR is generally a very useful technique, we did not perform these analyses on our samples. There are two main reasons for this choice. Classical NMR requires working in solution, possibly using a deuterated solvent. Even if a suitable solvent is available, information on the film would be lost, which would obviously be destroyed by solubilization. Alternatively, a solid-state NMR could be used, which would probably be more suitable, since these samples are solid due to the high gelation rate. However, these types of analyses are extremely complex and time-consuming. A solid-state NMR is not available to us.

 

2. What is the molecular weight of the polymer used?

This is a very important question. We have not measured the PM directly, but an average molecular weight is in the range 20,000–60,000 Da, according to the manufacturer’s specifications. Again, we have added this information to the main text.

 

3. Characterization analyses are missing, such as thermogravimetry, which is essential for these materials.

We agree again that thermal analyses are an important tool to investigate these materials, in particular to determine their thermal stability and to have important information to establish the polymerization and gelation mechanism. They also allow to know the mode of water release. However, in this specific case, we did not perform them mainly for reasons similar to those regarding NMR. One of the main problems is not to destroy the film and its structure, which could happen if you try to detach it from the support. Furthermore, the subsequent analyses were performed on dehydrated films, so the specific way of water loss is relatively unimportant. A more in-depth investigation of the thermal properties is however certainly very important and deserves adequate efforts, independent of this work which is mainly of synthesis.

4. FTIR characterization is missing.

We have answered this question previously.

 

5. The size of the silver particles obtained is not mentioned.

You are right that the size of the particles is important. They are very uniform, indicating that they formed rapidly, all or nearly all at the same time. We have evaluated the particle size distribution curve from the image analysis and have modified the main text accordingly and added a figure to illustrate this distribution curve.

 

6. How do the mechanical properties of the obtained material vary?

Again we agree with you that knowing the mechanical properties of these materials is very important, especially for possible applications, but as in the case of thermal properties, they deserve a deep and specific study. Future investigations will be necessary

 

7. If they are hydrogel films, how do they characterize the hydrogels? Water absorption capacity is missing, or contact angle tests are not performed.

Again we agree with you that knowing the mechanical properties of these materials is very important, especially for possible applications, but as in the case of thermal properties, they deserve a deep and specific study. Future investigations will be necessary. We have, however, studied the swalling behavior and added a figure to show it.

 

8. Figure 2 is not clear. It needs to be improved for better understanding.

For clarity and precision, we have combined figure 1 and figure 2, to try to better clarify the structure of the gel and the gelation process.

 

9. Further discussion is missing in the results and discussion section, but this is related to the poor characterization of the obtained materials.

We have tried to expand the discussion to respond as best as possible to these comments. The main text has been modified in accordance

 

Also, whenever it was necessary we added references to better support our work. With our best regards.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article presents a straightforward and accessible method for fabricating thin hydrogel films, including those embedded with silver nanoparticles, using a simple spin-coating technique. This approach stands out for its practicality—it avoids the need for pre-treated substrates or complex procedures, making it attractive for wider adoption. The in situ formation of nanoparticles directly within the hydrogel matrix adds further value by streamlining the fabrication process. The experimental setup is clear, and the authors effectively demonstrate how adjusting concentrations and spin speed can influence the film quality. They also apply a solid range of analytical techniques—SEM, UV-Vis, and XRD—to confirm the successful formation and even distribution of silver nanoparticles. Overall, the paper offers a practical contribution with promising implications for applications such as antimicrobial coatings and wound care materials.

However, I have a few questions or improvement suggestions:

The authors mention the homogeneity of the obtained films, but there is a lack of specific thickness measurements that would allow for a better assessment of their structure – for example, profilometry data would be useful here.

Although the physical cross-linking mechanism has been signaled, there is a lack of a broader perspective on how exactly the gelation process proceeds in time and space during centrifugation.

The work does not include information on the adhesion of the film to the substrate, its roughness or mechanical stability – and these are important features if we think about practical applications. In one place the authors write "good adhesion at the interface with the substrate" - but nowhere do they present the measurement methodology, results and their analysis leading to this conclusion

 

Author Response

The article presents a straightforward and accessible method for fabricating thin hydrogel films, including those embedded with silver nanoparticles, using a simple spin-coating technique. This approach stands out for its practicality—it avoids the need for pre-treated substrates or complex procedures, making it attractive for wider adoption. The in situ formation of nanoparticles directly within the hydrogel matrix adds further value by streamlining the fabrication process. The experimental setup is clear, and the authors effectively demonstrate how adjusting concentrations and spin speed can influence the film quality. They also apply a solid range of analytical techniques—SEM, UV-Vis, and XRD—to confirm the successful formation and even distribution of silver nanoparticles. Overall, the paper offers a practical contribution with promising implications for applications such as antimicrobial coatings and wound care materials.

The authors would like to thank the reviewer for his positive judgment on our work and for his useful comments. We are pleased that our ideas have been understood and appreciated and the reviewer's suggestions allow us to improve the quality of our work. In particular, we wanted to study the possibility of preparing nanoparticles in situ, directly in the matrix of a gel in the form of a film and to analyze the effects of the experimental conditions on their formation. We believe and hope that this approach in the future can be useful also for other types of nanoparticles and not "just" silver nanoparticles, which however have very interesting useful.

Hopefully, this type of materials could be useful in various sectors including the biomedical one.

 

However, I have a few questions or improvement suggestions:

The authors mention the homogeneity of the obtained films, but there is a lack of specific thickness measurements that would allow for a better assessment of their structure – for example, profilometry data would be useful here.

We agree with the reviewer's point about the importance of profilometry for these samples. Profilometry analysis is important to measure and analyze the surface topography of a material and in this way determine the main features a surface, including roughness, step heights, and other morphological features. The most efficient ways to perform profiling analyses is the atomic force microscopy, AFM. Unfortunately, at the present, we do not have the possibility to perform this type of analysis. However, we have used digital optical microscopy for this purpose and we have measured the thickness of the films. We have modified the main text according to these new results.

 

Although the physical cross-linking mechanism has been signaled, there is a lack of a broader perspective on how exactly the gelation process proceeds in time and space during centrifugation.

We have developed the explanation of the gelation process in this case based on the information available in the scientific literature and have therefore modified the main text accordingly.

 

The work does not include information on the adhesion of the film to the substrate, its roughness or mechanical stability – and these are important features if we think about practical applications. In one place the authors write "good adhesion at the interface with the substrate" - but nowhere do they present the measurement methodology, results and their analysis leading to this conclusion

Again, the study of mechanical properties is really very important, especially what concerns the adhesion of the films to the substrate. Initially, the statement about the good adhesion of the films was just an empirical observation. To better support it, we performed adhesion tests, described both in the experimental part and in the results. It should also be noted that the edge of the films is clean, there are no defects or damages. There are no traces of detachment of the film from the substrate in any area and this supports the idea that the films are well adhered.

In general, we have edited the manuscript text and figures, adding references where necessary to better support our claims.

 

With our best regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents an interesting approach to fabricating hydrogels and nanoparticle-loaded hydrogels via spin-coating. While the proposed method is promising, the manuscript contains numerous issues that must be addressed prior to consideration for publication. In particular, there are pervasive language problems, lack of clarity in expression, and insufficient supporting data. A major revision is required. Please consider the following specific comments:

1. The manuscript contains numerous grammatical and syntactical errors throughout. A thorough and professional English proofreading is essential.

2. (In abstract) The abstract should not merely describe the experimental procedure. It must clearly describe the background problem, how this study addresses it, and the significance of the results. These are currently lacking.

3. (In abstract) The expressions such as “If the viscosity is high and the rotation is slow” and “If the viscosity is low and the rotation is fast” are vague and imprecise. These statements should be rewritten to include quantitative or more scientifically rigorous descriptions.

4. (In introduction) The introduction lacks a proper review and analysis of relevant previous work. A concise summary of prior research and its limitations should be provided.

5. (In introduction) The novelty and contribution of this work are not clearly stated. 

6. Figures 1-3 can be merged into a single composite figure for conciseness and improved description.

7. Optical microscopy (or photographic) images of each process step are necessary for clear understanding of the fabrication procedure.

8. Basic mechanical property testing of the synthesized hydrogels (e.g., stress-strain curves) should be included.

9. Fundamental chemical characterization, such as FT-IR spectroscopy, is necessary to confirm hydrogel composition.

10. The SEM images presented in Figure 4 are out of focus and should be re-acquired with improved imaging quality.

11. Figures 6 and 7 lack explanations for subfigures (a, b, c, d); appropriate figure dscription should be provided.

12. There are two figures labeled as Figure 7. Additionally, the boundaries of the figures are cut off. The data should be re-plotted professionally with corrected figure labeling and resolution.

13. While SEM and XRD are used to confirm the presence of silver nanoparticles, additional optical microscopy (OM) data should be included to further support these findings.

Author Response

This manuscript presents an interesting approach to fabricating hydrogels and nanoparticle-loaded hydrogels via spin-coating. While the proposed method is promising, the manuscript contains numerous issues that must be addressed prior to consideration for publication. In particular, there are pervasive language problems, lack of clarity in expression, and insufficient supporting data. A major revision is required. Please consider the following specific comments:

We would like to thank the reviewer for appreciating the idea behind our work. We have tried to respond positively to all the comments that have been made, starting with the English of our manuscript

 

1. The manuscript contains numerous grammatical and syntactical errors throughout. A thorough and professional English proofreading is essential.

We have tried to improve the text, paying attention to all these errors and we have tried to improve the accuracy and precision of the text.

 

2. (In abstract) The abstract should not merely describe the experimental procedure. It must clearly describe the background problem, how this study addresses it, and the significance of the results. These are currently lacking.
3. (In abstract) The expressions such as “If the viscosity is high and the rotation is slow” and “If the viscosity is low and the rotation is fast” are vague and imprecise. These statements should be rewritten to include quantitative or more scientifically rigorous descriptions.

We have partially rewritten the abstract to accommodate these requests and observations, although we have tried to respect the maximum number of words allowed by the Journal for the abstract.

 

4. (In introduction) The introduction lacks a proper review and analysis of relevant previous work. A concise summary of prior research and its limitations should be provided.
5. (In introduction) The novelty and contribution of this work are not clearly stated. 

Based on the current scientific literature we have modified the text to add this requested information. However, it should be noted that the spin coating method has already been used for hydrogel films, but less frequently the gelation occurs during rotation, by direct reaction between the chemical components. Furthermore, what we consider an interesting element of novelty is that we have managed to prepare the nanoparticles directly in situ. In the future, one could even imagine that other particles of materials more complex than silver could be obtained with the same method, widening the range of possible applications

 

6. Figures 1-3 can be merged into a single composite figure for conciseness and improved description.

We agree with the fact that the first two figures can be merged together, because they concern the structure of the material itself and the gelation process and in this way we can be clearer and more precise, also for the understanding of a future potential reader. However, figure 3 is about the preparation method, which is specific to these samples. Therefore we think it is better to keep them separate. However, we have made some changes to make it clearer and more understandable as well.

 

7. Optical microscopy (or photographic) images of each process step are necessary for clear understanding of the fabrication procedure.

We agree that optical characterization is very useful to describe well the preparation process of our samples. Therefore we have added some figures and modified the main text accordingly.

8. Basic mechanical property testing of the synthesized hydrogels (e.g., stress-strain curves) should be included.

We have added some information about the mechanical properties of our materials. This also allows us to better evaluate the uniformity of the samples. However, the stress-strain curve is not trivial and easy to perform, because the samples are connected and bound to the substrate, which is much more rigid and resistant than the films. Therefore, the measurements would be affected by its presence.

 

9. Fundamental chemical characterization, such as FT-IR spectroscopy, is necessary to confirm hydrogel composition.

Again, we are in strong agreement on the importance of a spectroscopic characterization of the gel matrix. We have in any case, following your request, characterized our samples by FTIR spectroscopy and modified the manuscript text to describe the results thus obtained and added a figure to show the spectra. In general, they are in good agreement with the data reported in the literature, indicating that the gel matrix is indeed constituted by calcium alginate.

 

10. The SEM images presented in Figure 4 are out of focus and should be re-acquired with improved imaging quality.

We improved the quality of these figures

 

11. Figures 6 and 7 lack explanations for subfigures (a, b, c, d); appropriate figure dscription should be provided.

We have tried to improve the description of the figures by adding all the useful information

 

12. There are two figures labeled as Figure 7. Additionally, the boundaries of the figures are cut off. The data should be re-plotted professionally with corrected figure labeling and resolution.

We have corrected

 

13. While SEM and XRD are used to confirm the presence of silver nanoparticles, additional optical microscopy (OM) data should be included to further support these findings.

We add optical images

 

 

With our best regards

 

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript titled "A Simple Preparation of Thin Film of Hydrogels and Nanoparticle-loaded Hydrogels by Spin Coating Technique" explores the preparation and characterization of alginate-based hydrogel thin films by utilizing a spin-coating method. The films incorporate silver nanoparticles formed via an in-situ redox reaction, providing potential utility in biomedical and sensing applications. Overall, the manuscript is methodologically sound and systematically addresses film formation parameters, morphological characteristics, and nanoparticle distribution. However, several points require clarification, deeper analysis, or additional experiments to enhance the manuscript's completeness and impact.

 

Comment #1. The manuscript demonstrates a straightforward methodology for producing alginate-based hydrogel films via spin coating. However, the novelty of the spin-coating method applied here could be enhanced by explicitly discussing how the presented approach significantly differs or improves upon previously established techniques. The reviewer recommends adding a comparative analysis with other methods to highlight specific advantages or unique features of the spin coating approach in this context.

 

Comment #2. While the SEM images provided are qualitatively valuable, quantitative analyses such as film thickness distribution, particle density, or mechanical properties are limited. The reviewer suggests including additional quantitative characterization data, especially measurements of mechanical robustness (e.g., tensile strength, elasticity) or a statistical particle size distribution, to strengthen the manuscript.

 

Comment #3. Regarding the incorporation of silver nanoparticles, the manuscript thoroughly describes their synthesis and morphological analysis. However, potential cytotoxicity or biocompatibility assessments, even brief or preliminary, would greatly enhance the manuscript’s relevance, especially considering the biomedical applications mentioned by the authors. The reviewer recommends either conducting these preliminary assessments or clearly acknowledging this limitation in the Discussion.

 

Comment #4. The manuscript indicates that at high concentrations of reducing agents, undesired side reactions and crystal formation occur, damaging film integrity. The reviewer recommends providing a more detailed mechanistic explanation or additional characterization (e.g., elemental mapping and FTIR spectroscopy) to clarify the identity and distribution of these crystalline by-products, further elucidating their impact on film quality and functionality.

 

Comment #5. In the XRD analysis, several crystalline phases were observed and briefly discussed. However, the origins of these impurities and their impact on the hydrogel's functional properties remain somewhat speculative. The reviewer advises explicitly discussing potential strategies or recommendations to minimize or control the formation of these unwanted crystalline phases, which would be particularly valuable for practical applications.

 

Comment #6. The conclusion repeats several findings already thoroughly detailed in the results and discussion sections. The reviewer suggests condensing this section to focus more strongly on future directions, practical implications, and potential scalability or broader applicability of this spin-coating method in various industrial or biomedical settings.

 

Comment #7. Overall, the manuscript and figures currently demonstrate suboptimal quality and completion levels. In particular, some figures appear directly taken from previously published materials or reports without proper modifications. The reviewer strongly recommends the authors ensure all presented figures are original or sufficiently modified to clearly reflect the current work.

 

Comment #8. In practical applications, the separation of hydrogel coatings from substrates can be just as important as their formation. Therefore, the reviewer suggests including additional information regarding a stable and reproducible process for detaching hydrogel films from the substrate, emphasizing techniques that do not compromise the integrity of the films.

 

Comment #9. Several figure annotations (text, labels, and legends) are difficult to read due to their small font size, color choices, or layout. The reviewer advises improving readability by increasing font sizes, changing colors for better contrast, or rewriting annotations clearly and neatly within the figures.

 

Comment #10. The manuscript currently lacks sufficient statistical analyses and rigorous material characterization needed to fully confirm and understand the properties of the developed hydrogel films. To enhance reliability and credibility, the reviewer strongly recommends conducting additional statistical analyses and more comprehensive material characterization, such as swelling ratio measurements, mechanical property testing, rheological analysis, or quantitative nanoparticle distribution analyses. These additional data will significantly strengthen the scientific robustness and overall impact of the manuscript.

Author Response

The manuscript titled "A Simple Preparation of Thin Film of Hydrogels and Nanoparticle-loaded Hydrogels by Spin Coating Technique" explores the preparation and characterization of alginate-based hydrogel thin films by utilizing a spin-coating method. The films incorporate silver nanoparticles formed via an in-situ redox reaction, providing potential utility in biomedical and sensing applications. Overall, the manuscript is methodologically sound and systematically addresses film formation parameters, morphological characteristics, and nanoparticle distribution.

The authors would like to thank the reviewer for his judgment on our work and for appreciating the idea behind it.

 

However, several points require clarification, deeper analysis, or additional experiments to enhance the manuscript's completeness and impact.

 

Comment #1. The manuscript demonstrates a straightforward methodology for producing alginate-based hydrogel films via spin coating. However, the novelty of the spin-coating method applied here could be enhanced by explicitly discussing how the presented approach significantly differs or improves upon previously established techniques. The reviewer recommends adding a comparative analysis with other methods to highlight specific advantages or unique features of the spin coating approach in this context.

We appreciate this useful observation and accordingly we have modified the introduction, adding a discussion, which we hope is exhaustive, regarding the known preparation methods, trying to highlight the advantages of our technique, among which it should be mentioned the fact that it is possible to prepare the nanoparticles directly in situ

 

Comment #2. While the SEM images provided are qualitatively valuable, quantitative analyses such as film thickness distribution, particle density, or mechanical properties are limited. The reviewer suggests including additional quantitative characterization data, especially measurements of mechanical robustness (e.g., tensile strength, elasticity) or a statistical particle size distribution, to strengthen the manuscript.

The reviewer is certainly right in arguing that all these measures are absolutely useful for characterizing our samples. We've added the analysis of the particle size distribution curve (which actually turns out to be quite narrow) and a figure to show it.

Mechanical properties are also very important, especially for possible future applications. However, in this case it is not so easy to measure them, because they are linked to the support, which represents a rigid constraint, much more rigid and resistant than the films themselves. In any case, we have added some information about the mechanical properties of our materials. This also allows us to better evaluate the uniformity of the samples

 

Comment #3. Regarding the incorporation of silver nanoparticles, the manuscript thoroughly describes their synthesis and morphological analysis. However, potential cytotoxicity or biocompatibility assessments, even brief or preliminary, would greatly enhance the manuscript’s relevance, especially considering the biomedical applications mentioned by the authors. The reviewer recommends either conducting these preliminary assessments or clearly acknowledging this limitation in the Discussion.

We absolutely agree that this kind of characterization is of utmost importance especially for future medical applications of hydrogel films. But we disagree that this can be done "briefly" and we think that this deserves a complete study in itself. The point is that in our opinion to do this kind of study it is necessary to establish the correct design of the experiments in a very rigorous way. For example all biocompatibility experiments must be performed at least in triplicate to avoid spurious and random effects, other phenomena not necessarily related to the films or nanoparticles should be evaluated. The compatibility of the samples towards cells or bacteria could be limited simply by their non-permeability towards gases. Rigorous measurement protocols should be established. Bacterial tests can be performed on solid culture media, gels or agar agar beds, but this is not possible in the same way for eukaryotic cells that require liquid culture media.

However, we believe that an advantage of our samples is precisely their simplicity. In many cases, the synthesis of gels requires catalysts, initiators, solvents are needed and often free, unreacted monomers remain in the matrix. Almost always these chemicals are toxic or even very toxic. In our case they are absent precisely because of the gelation mechanism that requires only polymers and salt solutions. It may be necessary to adjust factors such as pH, but this can be done with simple washing. Therefore, following your advice, we have modified the discussion trying to highlight these difficulties and also the potential

 

Comment #4. The manuscript indicates that at high concentrations of reducing agents, undesired side reactions and crystal formation occur, damaging film integrity. The reviewer recommends providing a more detailed mechanistic explanation or additional characterization (e.g., elemental mapping and FTIR spectroscopy) to clarify the identity and distribution of these crystalline by-products, further elucidating their impact on film quality and functionality.

This is a good point and we have modified the discussion to try to clarify the mechanism that leads to the formation of these inorganic phases.

We also added a spectroscopic characterization to characterize the gels and their matrix.

 

Comment #5. In the XRD analysis, several crystalline phases were observed and briefly discussed. However, the origins of these impurities and their impact on the hydrogel's functional properties remain somewhat speculative. The reviewer advises explicitly discussing potential strategies or recommendations to minimize or control the formation of these unwanted crystalline phases, which would be particularly valuable for practical applications.

Again, this is a good point and we have tried to clarify in the main text the mechanism that leads to the formation of these phases. Above all, following your helpful suggestion, we tried to establish a strategy to avoid their formation.

However, some of these secondary phases, such as borax, while unwanted in the synthesis, are not necessarily bad, as they are not toxic or harmful.

 

Comment #6. The conclusion repeats several findings already thoroughly detailed in the results and discussion sections. The reviewer suggests condensing this section to focus more strongly on future directions, practical implications, and potential scalability or broader applicability of this spin-coating method in various industrial or biomedical settings.

Thanks for this suggestion, which we have made our own. We have at least partially rewritten the conclusions section, highlighting these points

 

Comment #7. Overall, the manuscript and figures currently demonstrate suboptimal quality and completion levels. In particular, some figures appear directly taken from previously published materials or reports without proper modifications. The reviewer strongly recommends the authors ensure all presented figures are original or sufficiently modified to clearly reflect the current work.

All the figures in this manuscript are original and derive from the authors' research, but have not been published in previous works. Obviously, for those that do not concern experimental data, we have taken inspiration from the scientific literature and from our previous works, but none derive from previously published works.

 

Comment #8. In practical applications, the separation of hydrogel coatings from substrates can be just as important as their formation. Therefore, the reviewer suggests including additional information regarding a stable and reproducible process for detaching hydrogel films from the substrate, emphasizing techniques that do not compromise the integrity of the films.

We agree with this point. We did not specifically address this point. The adhesion of the films is good, but it could be a limitation at the same time. This could be solved by using other substrates or by pre-treating them

 

Comment #9. Several figure annotations (text, labels, and legends) are difficult to read due to their small font size, color choices, or layout. The reviewer advises improving readability by increasing font sizes, changing colors for better contrast, or rewriting annotations clearly and neatly within the figures.

We fixed this problem

Comment #10. The manuscript currently lacks sufficient statistical analyses and rigorous material characterization needed to fully confirm and understand the properties of the developed hydrogel films. To enhance reliability and credibility, the reviewer strongly recommends conducting additional statistical analyses and more comprehensive material characterization, such as swelling ratio measurements, mechanical property testing, rheological analysis, or quantitative nanoparticle distribution analyses. These additional data will significantly strengthen the scientific robustness and overall impact of the manuscript.

We agree with these observations that are very useful for the characterization of these materials. We have added what is currently within our reach, with the instruments we have.

 

 

With our best regards

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors did not adequately respond to the requests; they simply sought an excuse or a response to avoid what was requested. As an expert in polymeric materials, I do not recommend this publication due to the weak characterization of the materials obtained in this research.

Reviewer 4 Report

Comments and Suggestions for Authors

The reviewer acknowledges that the authors have addressed the majority of substantial comments raised by the reviewer and recommends acceptance of this manuscript for publication in Coatings. However, the reviewer suggests that an additional comprehensive revision be performed to further enhance the readability and clarity of the article.