Advances in Hydrogel Film Fabrication and Functional Applications Across Biomedical and Environmental Fields

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The descriptions of film preparation techniques (e.g., solvent casting, spin coating, photolithography) on pages 5–11 are technical but not comparative.

There is no deep discussion on which methods are better suited for specific applications (e.g., biomedical vs. agricultural use).

The discussion on hydrogel stimuli-responsiveness (pages 3–4) and application-specific responsiveness (pages 17–20) have overlapping details.

Include a cross-reference matrix or case studies linking specific polymers + fabrication methods with their successful use in real-world applications (e.g., PVA via spin coating for drug delivery).

The discussion on toxicity and environmental sustainability of synthetic polymers (page 16–17).

Claims regarding smart/intelligent packaging (page 24–25).

Include it in the manuscript Cellulose 29 (2022) 2399–2411.

The manuscript requires moderate language polishing. There are several awkward phrases and run-on sentences that may hinder readability.

Manuscript tile is simple, please provide new one, here I have provided some possible title, you may choose.

“Advances in Hydrogel Film Fabrication and Functional Applications Across Biomedical and Environmental Fields"

"From Solvent Casting to Smart Coatings: A Comprehensive Review of Hydrogel Film Technologies and Uses"

"Multifunctional Hydrogel Films: Preparation Strategies, Polymer Systems, and Practical Applications

 

Author Response

Dear Reviewer Thank you very much for your comments: addressing them has allowed us to greatly improve the quality of our work.

 

The descriptions of film preparation techniques (e.g., solvent casting, spin coating, photolithography) on pages 5–11 are technical but not comparative.

There is no deep discussion on which methods are better suited for specific applications (e.g., biomedical vs. agricultural use).

We have added in the main text a more careful comparison of the methods and which method is preferable for specific applications.

The discussion on hydrogel stimuli-responsiveness (pages 3–4) and application-specific responsiveness (pages 17–20) have overlapping details.

We have tried to eliminate unnecessary repetitions.

Include a cross-reference matrix or case studies linking specific polymers + fabrication methods with their successful use in real-world applications (e.g., PVA via spin coating for drug delivery).

We have added a section dedicated to the real-world applications of hydrogel films, classified by material type.

The discussion on toxicity and environmental sustainability of synthetic polymers (page 16–17).

Similarly, we've added a section with updated references on these aspects. We've discussed the biocompatibility and cytotoxicity of hydrogel films and what can be done to overcome these problems.

Claims regarding smart/intelligent packaging (page 24–25).

Include it in the manuscript Cellulose 29 (2022) 2399–2411.

We have included this reference, changing the main text

The manuscript requires moderate language polishing. There are several awkward phrases and run-on sentences that may hinder readability.

We have improved the English of our manuscript and hope that the quality is better now.

Manuscript tile is simple, please provide new one, here I have provided some possible title, you may choose.

“Advances in Hydrogel Film Fabrication and Functional Applications Across Biomedical and Environmental Fields"

"From Solvent Casting to Smart Coatings: A Comprehensive Review of Hydrogel Film Technologies and Uses"

"Multifunctional Hydrogel Films: Preparation Strategies, Polymer Systems, and Practical Applications

We have changed the previous title, that was, actually, too general and vague. The new title is first you suggested

 

With our best regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. Title and Abstract:

• The title is too general. It would benefit from including more specific terms related to either the polymers used (e.g., “natural and synthetic polymers”) or the application field (e.g., “in biomedical and environmental technologies”).

• The abstract (lines 10–23) lacks a clear structure. It would be more informative if divided into four components: (1) background/purpose, (2) methods and materials discussed, (3) key applications or insights, and (4) a final sentence with a concise conclusion or relevance.

• Phrases such as “responding to external stimuli” are vague; the authors should mention the types of stimuli and clarify the novelty or scope of the review.

2. Introduction (lines 26–84):

• Lines 26–33 are overly dense and packed with technical language. Consider breaking this part into shorter, more digestible sentences. A clearer definition of gels vs. hydrogels would be useful, especially for interdisciplinary readers.

• Lines 34–41 introduce additives like nanoparticles and drugs, but without examples or citations. Including recent examples (preferably post-2019) would help.

• Lines 50–55 mention tunable properties but offer no concrete examples. A short sentence referencing how Ca²⁺ ions modify alginate, or how nanoparticles improve drug delivery, would be ideal.

• The final paragraph (lines 73–77) introduces the film focus, but this should appear earlier—preferably at the end of paragraph one—to clearly state the aim of the review.

3. Section on Preparation Methods (lines 86–314):

• This section is content-rich but difficult to follow due to the volume of information. Consider the following:

  1. Add more figures/tables to summarize pros and cons of each method beyond Table 1, which is helpful but insufficient.

  2. Many sub-sections (e.g., solvent casting, dip coating) are over-detailed for a review article. A more concise summary with cross-referenced citations would be appropriate.

  3. A comparison between these techniques in terms of biomedical compatibility, mechanical properties, scalability, and cost should be included explicitly in the text, not just in tabular form.

4. Materials for Hydrogel Films (from line 572):

• Section 3 is well-structured, dividing materials into natural and synthetic. However:

  1. Each subsection should end with a concise summary comparing the material’s performance in film form, not just as hydrogels in general.

  2. The section on chitosan lacks information on solubility, limitations in acidic pH, and chemical modification strategies (e.g., grafting, blending).

  3. The parts on cellulose and lignin go into very deep chemical detail. Some of this could be moved to supplementary material to maintain balance.

  4. In the lignin section, add a sentence discussing why it is underutilized in real applications despite its potential.

5. Applications (from line 823):

• The biomedical focus is strong, but:

  1. The environmental and agricultural applications section is underdeveloped. Expand with real examples (e.g., specific pesticide release systems, moisture-retaining films for crops).

  2. Lines 846–854 are useful for wound dressing, but lack discussion on challenges such as sterilization, skin adhesion, and long-term biostability.

  3. It would be beneficial to add a summary table mapping applications to specific polymers (e.g., PEG → drug delivery; alginate → wound healing).

6. General Form and Style:

• The manuscript contains many repetitions—for instance, the advantages of natural-origin hydrogels are repeated across multiple sections.

• English language quality should be improved. Some sentences are overly long, with convoluted structure. For example, line 30–31: “They are normally very homogeneous and, differently from most of the colloidal materials…” could be rephrased more clearly.

• Figures and figure captions often lack adequate referencing in the main text or are placed far from the relevant discussion (e.g., Figure 11, Figure 12). Ensure each figure is directly mentioned and interpreted in the narrative.

• Conclusion section is missing. A concise, clear final section should summarize:

  • (1) key takeaways from the review,

  • (2) comparative insights between materials/methods,

  • (3) outlook for future research or industrial use.

7. References:

• While many references are relevant, a substantial number are over 10 years old. Integrate at least 5–10 recent sources (2021–2024), especially regarding:

  • Biomedical applications (e.g., stimuli-responsive films)

  • Nanoparticle-loaded hydrogels

  • Sustainable materials in agriculture

• Consider referencing recent reviews on hybrid films or smart hydrogels in biosensing.

Author Response

Dear Reviewer Thank you very much for your interest in our work and especially for your helpful comments. We've tried to address them as best we can and hope you'll enjoy the new version.

 

1. Title and Abstract:

• The title is too general. It would benefit from including more specific terms related to either the polymers used (e.g., “natural and synthetic polymers”) or the application field (e.g., “in biomedical and environmental technologies”).
• The abstract (lines 10–23) lacks a clear structure. It would be more informative if divided into four components: (1) background/purpose, (2) methods and materials discussed, (3) key applications or insights, and (4) a final sentence with a concise conclusion or relevance.
• Phrases such as “responding to external stimuli” are vague; the authors should mention the types of stimuli and clarify the novelty or scope of the review.

We agree that the original title was too general and vague and have modified it to be more precise and to immediately clarify the purpose of our review.

In the same way and with the same logic we have rewritten the abstract, so that the purpose of the manuscript is immediately understandable.

 

2. Introduction (lines 26–84):

• Lines 26–33 are overly dense and packed with technical language. Consider breaking this part into shorter, more digestible sentences. A clearer definition of gels vs. hydrogels would be useful, especially for interdisciplinary readers.
• Lines 34–41 introduce additives like nanoparticles and drugs, but without examples or citations. Including recent examples (preferably post-2019) would help.
• Lines 50–55 mention tunable properties but offer no concrete examples. A short sentence referencing how Ca²⁺ ions modify alginate, or how nanoparticles improve drug delivery, would be ideal.
• The final paragraph (lines 73–77) introduces the film focus, but this should appear earlier—preferably at the end of paragraph one—to clearly state the aim of the review.

We have revised the introduction where required, also to make it more useful for future non-expert readers. We have added numerous references here (and in many other parts of the text), most of which are more recent than 2020. We have attempted to explain how the chemical and physical properties of gels can be controlled and regulated, including by controlling their chemical composition. Specifically, as requested, by controlling the concentration of ions such as Ca²⁺.

Finally, we tried to better explain the purpose of this review and how it differs from what can be found in the scientific literature.

 

3. Section on Preparation Methods (lines 86–314):

• This section is content-rich but difficult to follow due to the volume of information. Consider the following:
  1. Add more figures/tables to summarize pros and cons of each method beyond Table 1, which is helpful but insufficient.
  2. Many sub-sections (e.g., solvent casting, dip coating) are over-detailed for a review article. A more concise summary with cross-referenced citations would be appropriate.
  3. A comparison between these techniques in terms of biomedical compatibility, mechanical properties, scalability, and cost should be included explicitly in the text, not just in tabular form.

Following your suggestions, we've made many changes and eliminated unnecessary sections. In particular, we've tried to add a description of the advantages and disadvantages of the various methods, explaining the main applications of each.

 

4. Materials for Hydrogel Films (from line 572):

• Section 3 is well-structured, dividing materials into natural and synthetic. However:
  1. Each subsection should end with a concise summary comparing the material’s performance in film form, not just as hydrogels in general.
  2. The section on chitosan lacks information on solubility, limitations in acidic pH, and chemical modification strategies (e.g., grafting, blending).
  3. The parts on cellulose and lignin go into very deep chemical detail. Some of this could be moved to supplementary material to maintain balance.
  4. In the lignin section, add a sentence discussing why it is underutilized in real applications despite its potential.

We have added a summary, as requested, to describe the various types of materials and their uses. We've tried to explain why lignin isn't widely used and discussed chemical strategies (such as grafting or blending) to improve the polymers used for hydrogels and their performance.

 

5. Applications (from line 823):

• The biomedical focus is strong, but:
  1. The environmental and agricultural applications section is underdeveloped. Expand with real examples (e.g., specific pesticide release systems, moisture-retaining films for crops).
  2. Lines 846–854 are useful for wound dressing, but lack discussion on challenges such as sterilization, skin adhesion, and long-term biostability.

In this section, we've outlined the key challenges hydrogels will have to overcome in the future, such as sterilization and skin adhesion, and developed a section dedicated to agricultural applications, again with the support of numerous modern references. We've also discussed pesticide and fertilizer release in greater detail.

3. It would be beneficial to add a summary table mapping applications to specific polymers (e.g., PEG → drug delivery; alginate → wound healing).

We believe this is an excellent observation. That's why we've added an entire section on real-world and modern applications of hydrogel films, classifying them by material.

6. General Form and Style:

• The manuscript contains many repetitions—for instance, the advantages of natural-origin hydrogels are repeated across multiple sections.
• English language quality should be improved. Some sentences are overly long, with convoluted structure. For example, line 30–31: “They are normally very homogeneous and, differently from most of the colloidal materials…” could be rephrased more clearly.
• Figures and figure captions often lack adequate referencing in the main text or are placed far from the relevant discussion (e.g., Figure 11, Figure 12). Ensure each figure is directly mentioned and interpreted in the narrative.

We corrected all these points, especially trying to improve the English of our manuscript.

• Conclusion section is missing. A concise, clear final section should summarize:
  • (1) key takeaways from the review,
  • (2) comparative insights between materials/methods,
  • (3) outlook for future research or industrial use.

As with the abstract and introduction, we have rewritten the conclusions to improve them and make them more satisfying.

7. References:

• While many references are relevant, a substantial number are over 10 years old. Integrate at least 5–10 recent sources (2021–2024), especially regarding:
  • Biomedical applications (e.g., stimuli-responsive films)
  • Nanoparticle-loaded hydrogels
  • Sustainable materials in agriculture
• Consider referencing recent reviews on hybrid films or smart hydrogels in biosensing.

We have added a section dedicated to hydrogel film-based biosensors, which is indeed a very important topic and was missing in the first version.

As for the bibliography of our manuscript, in fact, to better support our points, we have added many references, the majority more recent than 2020 and many from 2025.

 

With our best regards,

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

I have gone through the review article “Preparation and applications of hydrogel films” (Manuscript number: applsci-3806159) presented by Alberto Ubaldini and Sara Calistri from the University of Bologna. The authors describe a broad review focusing on some interesting applications of hydrogel/films systems.

 

The main goals of the manuscript:

-Different hydrogel materials were summarized with biomedical applications (mainly drug delivery, wound healing, and tissue engineering).

-Both classical and advanced synthetic procedures for hydrogel materials are reported.

 

References: Are not appropriate and not up to date with respect to the subject matter covered. There are many reports for new synthetic strategies related to increase the mechanical resistance of hydrogel materials for biomedical and environmental applications. However, the main goal of the review is not clear (it can be defined in the tittle as well in the abstract).

 

Some points need to be addressed:

1) The title is not informative about the topics that will be covered in this review.

2) Chemical structures must be drawn using standard styles (check the editorial instructions). In Figure 14 check the bond angles/distances in the chemical structures. Also, the font size is different among the chemical compounds.

3)  Line 684, check the bold style used.

4) The use of MOF particles is particularly important in order to increase the mechanical properties for different applications. It is recommended to explore this aspect in this review with relevance in biomedical uses. Furthermore, there are many uses of metal nanoparticles (both metallic and/or polymeric nanoparticles) included onto films/hydrogels for antibacterial applications in wound healing and tissue engineering.

5) Also, some physical improvements can be done using ionic crosslinking when the hydrogel system can be protonated or coordinated with metal ions. This aspect is relevant for the smart release of drugs in different films.

6) A brief comment related to the main characterization techniques can be added in order to increase the impact of the review (for example, from chemical characterization such as HRMAS NMR, XPS, ICP-MS to both mechanical and microcopy techniques: SEM/HRTEM and EDAX). In this sense, the reproducibility of the synthetic methods must be guaranteed using techniques that demonstrate the robustness of these procedures as well the inclusion of nanosystems or chemical modifications of hydrogel films.

7) Once again, check the chemical structures in Figure 15.

8) Figure 16, different font/chemical styles can be clearly detected form the structures.

9) Microwave or assisted synthetic technologies may be added in this review to explore other obtention procedures for hydrogel materials.

10) The section “4.3 Other applications” can be expanded, there are many advances in the different areas.

11) While the conclusion section summarizes the results of the review related to the synthesis of hydrogel movies, it lacks a discussion on future research addresses of the different materials explored here. Strengthening the conclusion with broader implications of the results can be good for new directions in biomedical and environmental uses.

Final remarks: It is a potential and interesting review; however, some changes and suggestions can increase the level and the presentation of this manuscript. Particularly, the presentation of the chemical structures must be properly corrected. I hope the team of authors would like to respond to the mentioned points and revise the review accordingly.

Author Response

Dear Reviewer Thank you very much for your comments: addressing them has allowed us to greatly improve the quality of our work.

I have gone through the review article “Preparation and applications of hydrogel films” (Manuscript number: applsci-3806159) presented by Alberto Ubaldini and Sara Calistri from the University of Bologna. The authors describe a broad review focusing on some interesting applications of hydrogel/films systems.

 

The main goals of the manuscript:

-Different hydrogel materials were summarized with biomedical applications (mainly drug delivery, wound healing, and tissue engineering).

-Both classical and advanced synthetic procedures for hydrogel materials are reported.

 

References: Are not appropriate and not up to date with respect to the subject matter covered. There are many reports for new synthetic strategies related to increase the mechanical resistance of hydrogel materials for biomedical and environmental applications. However, the main goal of the review is not clear (it can be defined in the tittle as well in the abstract).

We have added in the revised version many reference: the vast majority are more recent than 2020, and many are from 2025.

We have revised the introduction and we tried to better explain the purpose of this review and how it differs from what can be found in the scientific literature.

Some points need to be addressed:

• The title is not informative about the topics that will be covered in this review.

We agree, the initial title was too generic and vague and therefore we changed it

• Chemical structures must be drawn using standard styles (check the editorial instructions). In Figure 14 check the bond angles/distances in the chemical structures. Also, the font size is different among the chemical compounds.

We have revised the chemical structure, trying to correct all the mistakes and imprecisions.

• Line 684, check the bold style used.

We have corrected

• The use of MOF particles is particularly important in order to increase the mechanical properties for different applications. It is recommended to explore this aspect in this review with relevance in biomedical uses. Furthermore, there are many uses of metal nanoparticles (both metallic and/or polymeric nanoparticles) included onto films/hydrogels for antibacterial applications in wound healing and tissue engineering.

We have added a section dedicated to the main additives that can be added to hydrogel films, explaining their nature and possible effects, with many supporting references.5) Also, some physical improvements can be done using ionic crosslinking when the hydrogel system can be protonated or coordinated with metal ions. This aspect is relevant for the smart release of drugs in different films.

• A brief comment related to the main characterization techniques can be added in order to increase the impact of the review (for example, from chemical characterization such as HRMAS NMR, XPS, ICP-MS to both mechanical and microcopy techniques: SEM/HRTEM and EDAX). In this sense, the reproducibility of the synthetic methods must be guaranteed using techniques that demonstrate the robustness of these procedures as well the inclusion of nanosystems or chemical modifications of hydrogel films.

Again, we have added a section dedicated to characterization methods, which is certainly a very important topic and was missing from the first version. We thank you for this observation, which allowed us to correct a bug.

7) Once again, check the chemical structures in Figure 15.

8) Figure 16, different font/chemical styles can be clearly detected form the structures.

We have corrected

9) Microwave or assisted synthetic technologies may be added in this review to explore other obtention procedures for hydrogel materials.

We have modified the main text to present the preparation via microwave route, that is very important.

10) The section “4.3 Other applications” can be expanded, there are many advances in the different areas.

We have added some part dedicated to biosensing that is very important and we have expanded the rest. Indeed, we have added a section dedicated to the real applications of hydrogel films.

11) While the conclusion section summarizes the results of the review related to the synthesis of hydrogel movies, it lacks a discussion on future research addresses of the different materials explored here. Strengthening the conclusion with broader implications of the results can be good for new directions in biomedical and environmental uses.

We have change where necessary the main text in according to this point.

Final remarks: It is a potential and interesting review; however, some changes and suggestions can increase the level and the presentation of this manuscript. Particularly, the presentation of the chemical structures must be properly corrected. I hope the team of authors would like to respond to the mentioned points and revise the review accordingly.

Thank you very much for your positive feedback on our work, and we hope we have responded positively to your comments.

 

With our best regards

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript covers a highly relevant and rapidly developing field. The content is extensive, and the structure is logical, moving from fundamental concepts to specific applications. The manuscript requires significant revisions, particularly in terms of organization, clarity of language, and the quality of figures, before it can be considered for publication.

• The review primarily describes findings from other papers without offering a critical perspective or synthesizing the information into a new framework. For example, it lists different preparation methods but does not provide a critical comparison of their trade-offs in terms of cost, scalability, or resulting film properties.
• The introduction does not effectively state what makes this review unique. What new synthesis or perspective does it offer that other reviews on hydrogels and hydrogel films do not? This needs to be explicitly stated and reinforced throughout the text. The introduction should be rewritten to more clearly state the specific gap in the literature that this review addresses. What unique contribution does this review offer to the field of hydrogel films? please explain

• Figure 1 and 2: Please replace these figures with high-resolution versions. The text within the diagrams is currently illegible. Ensure all figures are of professional quality.

• Please add a comparative table in Section 2.1, or a more detailed discussion that summarizes the pros and cons of each method (e.g., solvent casting vs. spin coating) in terms of scalability, cost, film uniformity, and mechanical properties. This would be a significant value-add for the reader.

• Consider reorganizing Applications section. Instead of a simple list of applications, please structure it around the key properties of the films. For example, a subsection on "Stimuli-Responsive Films" could cover sensors, drug delivery, and smart textiles, highlighting the common principle.

I recommended that this review be considered for publication but after MAJOR revision.

Comments on the Quality of English Language

The text contains some awkward phrasing and grammatical errors that impede the flow of reading. The language needs to be professionally edited to improve clarity and precision.

Author Response

Dear Reviewer

Thank you very much for your comments: addressing them has allowed us to greatly improve the quality of our work.

The manuscript covers a highly relevant and rapidly developing field. The content is extensive, and the structure is logical, moving from fundamental concepts to specific applications. The manuscript requires significant revisions, particularly in terms of organization, clarity of language, and the quality of figures, before it can be considered for publication.

• The review primarily describes findings from other papers without offering a critical perspective or synthesizing the information into a new framework. For example, it lists different preparation methods but does not provide a critical comparison of their trade-offs in terms of cost, scalability, or resulting film properties.

We have modified this part of the text, adding a comparison between the techniques, trying to highlight which are most suitable for certain applications and the advantages and disadvantages they have.

• The introduction does not effectively state what makes this review unique. What new synthesis or perspective does it offer that other reviews on hydrogels and hydrogel films do not? This needs to be explicitly stated and reinforced throughout the text. The introduction should be rewritten to more clearly state the specific gap in the literature that this review addresses. What unique contribution does this review offer to the field of hydrogel films? please explain

We have revised the introduction where required, also to make it more useful for future non-expert readers. We have added numerous references here (and in many other parts of the text), most of which are more recent than 2020. We have attempted to explain how the chemical and physical properties of gels can be controlled and regulated, including by controlling their chemical composition. Specifically, as requested, by controlling the concentration of ions such as Ca²⁺.

Finally, we tried to better explain the purpose of this review and how it differs from what can be found in the scientific literature.

• Figure 1 and 2: Please replace these figures with high-resolution versions. The text within the diagrams is currently illegible. Ensure all figures are of professional quality.

We have improved the quality of the figures.

• Please add a comparative table in Section 2.1, or a more detailed discussion that summarizes the pros and cons of each method (e.g., solvent casting vs. spin coating) in terms of scalability, cost, film uniformity, and mechanical properties. This would be a significant value-add for the reader.

At your suggestion, we did just that. We tried to compare the techniques, highlighting which are better for certain applications and not for others.

• Consider reorganizing Applications section. Instead of a simple list of applications, please structure it around the key properties of the films. For example, a subsection on "Stimuli-Responsive Films" could cover sensors, drug delivery, and smart textiles, highlighting the common principle.

We have added a section dedicated to real-world applications of hydrogel films, classified by material. Indeed, the rationale for our review was to present, even to a non-expert reader, the general principles of everything related to hydrogel films. But a discussion of real-world cases was missing, and we thank you for highlighting this point. We have tried to remedy this.

 

I recommended that this review be considered for publication but after MAJOR revision.

           

Thank you very much for your positive feedback on our work, and we hope we have responded positively to your comments.

 

With our best regards

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Some references are incomplete, for ex, ref. no 159 and others

Author Response

Dear Reviewer

 

Thank you for reporting these errors in the references. We've fixed them

With our best regards

Reviewer 3 Report

Comments and Suggestions for Authors

All the previous points/questions have been addressed carefully in the new version of the manuscript. It is a very well conducted and valuable review for the synthesis and applications of hydrogel films in biomedical and environmental fields.

Author Response

Dear Reviewer

Thank you very much for your positive review of our work.

 

Best regards,

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have accepted all suggestions so I recommend publishing the paper after English proofreading.

Author Response

Dear Reviewer

Thank you very much for your positive review of our work.

 

Best regards,