Designing Viscoelastic Gelatin-PEG Macroporous Hybrid Hydrogel with Anisotropic Morphology and Mechanical Properties for Tissue Engineering Application
Round 1
Reviewer 1 Report
In this study, authors prepared gelatin-PEG based hybrid hydrogel and studied its different properties. I urge the authors to address the following comments:
1. There are some grammatical mistakes in the manuscript. Please revise it thoroughly.
2. Identify the problem through literature review.
3. Please clearly mention the aim and objective of the work.
4. What is new and novel in this study beyond the already reported literature.
5. Give the rationale for the selection of protocol for the production of hydrogel
6. How PEG was functionalized? and which functional groups were attached?
7. Please provide the proposed mechanism among the ingredients.
8. For which application, these hydrogels were prepared?
9. Authors claimed these hydrogels for tissue engineering, then antibacterial and cytotoxicity behaviour should be evaluated.
10. Please cite some latest references of the respective journal.
Author Response
Dear author,
Please find the attached file.
Thanking you,
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors propose a simpler method of forming a cross-linked Gel-PEG hydrogel suitable for a wide range of biomedical technologies.
Comments and questions:
Materials and methods
1. Based on what data was the ratio of Gel-PEG (wt.%) 81: 19 selected? 1.6 g of functionalized PEG was used for crosslinking in 65 ml of solution (approximately 25 g/l), which, with a molecular weight of the PEG diepoxy derivative of about 500 daltons, is 0.05 mol. Judging by the fact that glutaraldehyde has recently been used mainly with a concentration of 0.02 M (0.2%), the concentration of the crosslinking agent chosen by the authors is excessive, which makes it possible to predict the presence of a large number of non-reacted epoxy groups (the bifunctional crosslinking agent is associated with gelatin only by one group, and the second remained inactive), and this may adversely affect the cytoxicity of a scaffold. Since the hydrogel is designed for biomedical use, it is advisable to investigate its cytotoxicity.
2. The pH of the solution should be given.
3. It is necessary to justify why the option with crosslinking was chosen before cryostructuring, and not after freezing and lyophilization, as is usually done.
4. There is no information about the methods of the statistical processing of experimental data, including the sample size (n).
Results and Discussion
1. It is desirable to provide data on the distribution of pores by size or the values of the average diameter of the pores.
2. From the work on the formation of cryogels, it is known that for each of the objects there is an optimal freezing temperature, which makes it possible to obtain a frame with sufficiently large pores, the size of which is optimal from the point of view of interaction with cells. In the case of gelatin, this temperature is about -20 degrees. The authors should justify why the freezing temperature of -196 degrees was chosen? It is known that the higher the cooling rate, the more crystals are formed and the smaller their size (source: https://www.activestudy.info/zamorazhivanie-vody /), which we observe in the case of the proposed scaffolding. It is known that for tissue engineering and regenerative medicine technologies, preference is given to macroporous cryogels with high porosity. The relatively low porosity of hydrogels obtained by the proposed method limits their use in the TERM technologies. I advise the authors to discuss this issue.
3. The observed hydrolytic resorption of the scaffold may be largely due to the resorption of unstitched gelatin. I note that the main mechanism of the degradation of scaffolds from gelatin (collagen) in the body is its enzymatic cleavage (collagenase).
Author Response
Dear reviewer,
Please find the attached file herewith.
Thanking you,
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript is very interesting, describing in a very detailed way the characteristics of the obtained hydrogel material, in particular its mechanical properties. However, in my opinion, the manuscript needs thorough revision, re-editing, and improvement before being considered for further publication.
Main remarks on the manuscript:
1. The text requires thorough linguistic and stylistic correction. In its current form, it contains a lot of incomprehensible phrases; some sentences are very long and complex; some of the expressions used are colloquial and rather not found in scientific texts (e.g. ‘elegant … (ability)’ line 48; ‘might be blessing for’ line 283).
2. There is a lack of discussion of research results in relation to the current literature. In its current form, the description of the results resembles a very detailed academic report on the experiments performed. However, without referring the properties of the hydrogel characterized in the work to specific values obtained by other scientists for similar materials (or materials for the same practical applications), it is impossible to estimate its actual application potential.
The manuscript must be supplemented with such a comparative discussion of the results at the end of section 3 (Results and discussion) or in section 4 (Conclusions).
3. The size of all graphs given in the manuscript should be unified.
4. Unify the description of obtained material – use one of these à ‘Gel-PEG hydrogel’ or ‘G/PEG hydrogel’ in the whole text.
5. Update the references of current literature reports. In this form, there are only 2, 3 and 2 references from 2022, 2021 and 2020, respectively.
Detailed remarks on the manuscript:
1. Page 1, Lines 3 and 14; Page 10, Line 335; and others – change ‘mechanical property’ to ‘mechanical properties’.
2. Page 2, Line 69 – Authors are asked to explain what ‘excellent versatile properties’ they might in mind here.
3. Page 2, Line 82 – Authors are asked to put the references to the literature here.
4. Page 4, Line 146 – change the word ‘measured’ to ‘determined’
5. Page 5, Line 235 – I suggest changing the word ‘recipe’ to ‘procedure’
6. Page 6, Line 250 - I suggest changing the word ‘recipe’ to ‘composition’
7. Page 6, Line 257 – I would like to ask the Authors if they are sure that by FTIR they could characterize the hydrogel structure. In my opinion, this technique refers to determining the composition of a given sample.
8. Page 7, Line 272 – I would like to ask the Authors to mark the peak characteristic for gelatin (at 3300 cm-1) in Figure 2, as well as to use ‘Gel’ instead of ‘G’ and ‘Gel-PEG’ instead ‘G/PEG’.
9. Page 7, Line 273 – Authors are asked to change the caption of Figure 2 to ‘FTIR spectra of pure starting components (Gel, PEG) and Gel-PEG hybrid hydrogel.
10. Page 7, Line 282 – Authors are asked to check the spelling of the word ‘avid’. I suppose that you meant ‘avoid’.
11. Page 11, Lines 346-347 – there is a direct repetition of the same values given in Table 2. Please decide if you show the results in the table or if you put the obtained values in the text.
12. Page 11, Line 364 – In my opinion, Figure 9 should be placed near its first citation in the text (in current form Fig. 9 appear 3 pages later).
13. Page 12, Lines 382-286 – the size of the font should be changed according to the other figure captions.
14. Page 18, Table 4 – there is no citation of Table 4 in the text. Please remember that is should be given before the Table appears.
Comments for author File: Comments.pdf
Author Response
Dear reviewer,
Please find the attached file herewith.
Thanking you,
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Authors have addressed the comments adequately.
Reviewer 2 Report
no comments
Reviewer 3 Report
I would like to thank the Authors for referring to all my remarks. I recommend an article for further publication procedure.
