Antifouling Performance and Long-Term Efficiency of a Zwitterionic Sulfobetaine-Hydroxyethyl-Containing Polymethylmethacrylate Ter-Co-Polymer Coating Against Biomass-Producing Photosynthetic Strains

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The PSBM coating preparation method only refers to "according to established procedures" and lacks specific parameters (such as initiator concentration and polymerization time).
2. No statistical test (such as ANOVA) was conducted to verify the significance of differences between groups, and the conclusion was drawn only by numerical comparison, which was not convincing enough.
3. Biomass data (e.g. wet weight, cell density) did not establish a quantitative association with pollution resistance, weakening the depth of mechanism interpretation.
4. The performance difference between PSBM and other commercial anti-fouling coatings (such as PEG and PDMS) was not compared, and the competitive analysis was lacking.
5. The long-term failure mechanism of PSBM coating (such as mechanical wear and chemical degradation) has not been deeply discussed, which limits the guiding value of practical application.
6. The cited literature focuses on the year before 2020 and does not include recent breakthroughs in the field of zwitterionic polymers (such as dynamically responsive coatings and bionic surface design), which is not frontier enough.

Comments on the Quality of English Language

No

Author Response

Response to reviewers:

First of all, we would like to thank the reviewers for their useful comments. We modify the manuscript accordingly with them.

 

Here you will find punctual answers to the reviewers’ comments

 

Reviewer nr 1

Comments and Suggestions for Authors

 

1. The PSBM coating preparation method only refers to "according to established procedures" and lacks specific parameters (such as initiator concentration and polymerization time

Response: Thank you for the suggestion.

Accordingly, the sentence page 2, line 67-69 “Due to well established synthetic procedures, etc.” was removed. Furthemore, synthetic details, regarding both PSBM polymer and basic casting mixture used to obtain PSBM coated PMMA coupons, have been added in the experimental section.

 

1. No statistical test (such as ANOVA) was conducted to verify the significance of differences between groups, and the conclusion was drawn only by numerical comparison, which was not convincing enough

Answer: Statistical analysis was carried out and reported in tables 1 and 2.

 

3. Biomass data (e.g. wet weight, cell density) did not establish a quantitative association with pollution resistance, weakening the depth of mechanism interpretation

Answer: Biomass weight was not so relevant, but allow us to establish that the growth conditions were optimal for testing the AF properties of the different coupons.

 

4. The performance difference between PSBM and other commercial anti-fouling coatings (such as PEG and PDMS) was not compared, and the competitive analysis was lacking.

A new sentence regarding the greater chemical stability of zwitterionic systems compared to PEG ones was added (see page 2, lines 73-79).

            We also introduced a new sentence (Pag 11-12, lines 485-499) on the results obtained using PDMS@PEG amphiphilic systems, to support the validity of hydrogel technology for obtaining antifouling coatings.

Aim of the paper, besides to studying the PSBM coating stability over more cycles, was to check its AF activities vs different strains commonly used as models compared to untreated PMMA surfaces. PSBM features only 10% of ZW sulfobetaine groups and its antifouling activity vs other species was not predictable.

 

5. The long-term failure mechanism of PSBM coating (such as mechanical wear and chemical degradation) has not been deeply discussed, which limits the guiding value of practical application.

Thank you for your comment.

No mechanical wear tests have been performed. Test regarding the chemical stability of PSBM in algal media have been performed  before starting with the AF investigations.

In this regard, a new sentence (pag 9, lines 300-302) was added as follows: “Furthemore, PSBM displays remarkable chemical stability in algal media (pH 7–9, ionic strength ~0.5M), aligning with the known resistance to hydrolysis resistance of PMMA zwitterionic polymers [27].

 

6. The cited literature focuses on the year before 2020 and does not include recent breakthroughs in the field of zwitterionic polymers (such as dynamically responsive coatings and bionic surface design), which is not frontier enough

The literature has been focused on zwitterionic species for PBRs application. However, a recent report regarding their smart behaviour, mainly in medical field, has been added. See refs: 31. Other more recent refs have been added, namely 10,11, 30,31 and 33,34.

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript ID- coatings-3558110

The manuscript entitled “Antifouling performance and long-term efficiency of a zwitterionic Sulfobetaine-Hydroxyethyl containing-Polymethylmethacrylateter-co-polymer coating against biomass producing photosynthetic strains”

This study investigates, PSBM-coated PMMA surfaces that showed reduced biofilm formation and maintained high antifouling efficacy after repeated exposure to photosynthetic strains, demonstrating its potential for use in photobioreactors. Although the study is thoroughly conducted and well-written, I have the following suggestions that could enhance the overall quality of the manuscript.

 

1. The author should explain the antifouling mechanism to clarify which factors contribute to its effectiveness, such as hydrophobicity, electrostatic interaction, or others.
2. The author should incorporate the standard deviation for most of the experiments, including those presented in Table 1, Table 2, Table 3, and Figures 3, 5, and 6, to provide a clearer understanding of the data.
3. All abbreviations should be spelled out when first mentioned in the manuscript. For example, PEG, PA, and ZW should be defined in the introduction.
4. In Table 1, the value of % Area is written as 7,5 and 5,33, it should be 7.5 and 5.33 respectively.
5. The author should ensure consistent formatting for the titles of the tables and figures. Table 1 is italic, while Tables 2 and 3 are not (similarly for the figure). The formatting should be uniform throughout the paper.
6. The author should compare the antifouling performance of the current material with other listed materials to highlight its significance.
7. The author should check all the references, such as adding the page number for reference 10 and removing PP from reference no. 33.
   
   

Author Response

Response to reviewers:

First of all, we would like to thank the reviewers for their useful comments. We modify the manuscript accordingly with them.

 

Here you will find punctual answers to the reviewers’ comments

Reviewer nr. 2                                                    

 

This study investigates, PSBM-coated PMMA surfaces that showed reduced biofilm formation and maintained high antifouling efficacy after repeated exposure to photosynthetic strains, demonstrating its potential for use in photobioreactors. Although the study is thoroughly conducted and well-written, I have the following suggestions that could enhance the overall quality of the manuscript.

 Answer: Thank you for your opinion regarding the manuscript.

 

1. The author should explain the antifouling mechanism to clarify which factors contribute to its effectiveness, such as hydrophobicity, electrostatic interaction, or others.

In a previous paper (see ref 42) we have reported on the chemico-physical characterization of PSBM and, in particular, on their behavior in the presence of electrolytes.  As we have reported, we were not able to produce WCA data by captive bubble methods, which could be indicative of the water layer formation. Regarding the mechanism we have suggested that a synergic action of ZW and HEMA component was suggested.

 

2. The author should incorporate the standard deviation for most of the experiments, including those presented in Table 1, Table 2, Table 3, and Figures 3, 5, and 6, to provide a clearer understanding of the data

Answer: S.D and ANOVA were applied and reported in Tables 1 and 2.

 

3. All abbreviations should be spelled out when first mentioned in the manuscript. For example, PEG (Polyethylene Glycol), PA (Polyamide), and ZW (Zwitter ionic) should be defined in the introduction.

            Answer: Thank you for your suggestion. It was done.

 

4. In Table 1, the value of % Area is written as 7,5 and 5,33, it should be 7.5 and 5.33 respectively

            Answer: Table 1 was fully corrected.

 

5. The author should ensure consistent formatting for the titles of the tables and figures. Table 1 is italic, while Tables 2 and 3 are not (similarly for the figure). The formatting should be uniform throughout the paper.

Thank you. It was done.

 

6. The author should compare the antifouling performance of the current material with other listed materials to highlight its significance.

            A new sentence regarding the greater chemical stability of zwitterionic systems compared       to PEG ones was added (see page 2, lines 73-79).

            We also introduced a new sentence (Pag 11-12, lines 485-499) on the results obtained using PDMS@PEG amphiphilic systems, to support the validity of hydrogel technology for         obtaining antifouling coatings.

            Aim of the paper, besides to studying the PSBM coating stability over more cycles, was to         check its AF activities vs different strains commonly used as models compared to untreated             PMMA surfaces. PSBM features only 10% of ZW sulfobetaine groups and its antifouling             activity vs other species was not predictable.

 

7. The author should check all the references, such as adding the page number for reference 10 and removing PP from reference no. 33 (Number 10 is corrected but 33 is a book chapter)

      Thank you. It was done

 

8. The author should explain the antifouling mechanism to clarify which factors contribute to its effectiveness, such as hydrophobicity, electrostatic interaction, or others.

 

In a previous paper (see ref 42) we have reported on the chemico-physical characterization        of PSBM and, in particular, on their behavior in the presence of electrolytes.  As we have           reported we were not able to produce WCA data by captive bubble methods, which could      be indicative of the water layer formation. Regarding the mechanism we have suggested          that a synergic action of ZW and HEMA component was suggested.