Effect of PLGA Concentration in Electrospinning Solution on Biocompatibility, Morphology and Mechanical Properties of Nonwoven Scaffolds
, Anastasia G. Drozd 1, Evgenii V. Plotnikov 1,2, Gleb E. Dubinenko 1, Anna I. Kozelskaya 1, Sven Rutkowski 1,* and Sergei I. Tverdokhlebov 1,*Round 1
Reviewer 1 Report
The manuscript reports the effect of weight concentration on the properties of polymeric scaffolds of poly(lactide-co-glycolide) prepared by electrospinning. However, there are few problems in the manuscript, which should be minor revised.
1. There are a number of publications of electrospun PLGA scaffolds on the concentration of polymer in the electrospinning solution. Please cite the literature comprehensively and explain the representative work.
2. What are the unique ideas behind the research as compared to previous reported work? Why it is worth to knowing?
3. In the degradation study, all PLGA samples did not change their mass significantly after immersion in PBS. The author thought that the degradation of PLGA scaffolds did not reach the third step (the constant degradation step). But none of the test or data can support the conclusion in the maunscript. Please supplement experiments of molecular weight of PLGA after immersion in PBS.
Minor editing of English language required.
Author Response
The manuscript reports the effect of weight concentration on the properties of polymeric scaffolds of poly(lactide-co-glycolide) prepared by electrospinning. However, there are few problems in the manuscript, which should be minor revised.
General answer: We thank the reviewer very much for reviewing our manuscript and for the useful comments. We revised the manuscript in accordance with your comments. All changes are marked in green in the main manuscript text and the support information manuscript.
Comment 1: There are a number of publications of electrospun PLGA scaffolds on the concentration of polymer in the electrospinning solution. Please cite the literature comprehensively and explain the representative work.
Answer 1: We thank the reviewer for this helpful comment. The introduction and the discussion has been improved according to this comment. We have added information with references that explain in more detail the effect of polymer concentration on the morphological, mechanical and biological properties of electrospun scaffolds.
Comment 2: What are the unique ideas behind the research as compared to previous reported work? Why it is worth to knowing?
Answer 2: We thank the reviewer for these important questions. In fact, there is a large number of studies devoted to the investigation of the dependence of the morphological and biological properties of electrospun scaffolds on the polymer concentration in the electrospinning solution. Nevertheless, there are conflicting information in these research papers investigating the effects of polymer concentration on the properties of electrospun scaffolds. We have tried to point out this issue in the introduction. Therefore, this work is aims to clarify how the polymer concentration effects on the morphological, mechanical, and biological properties of electrospun PLGA scaffolds. This should have been made clearer by the changes in the introduction.
Comment 3: In the degradation study, all PLGA samples did not change their mass significantly after immersion in PBS. The author thought that the degradation of PLGA scaffolds did not reach the third step (the constant degradation step). But none of the test or data can support the conclusion in the maunscript. Please supplement experiments of molecular weight of PLGA after immersion in PBS.
Answer 3: We thank the reviewer very much for this very helpful comment. Molecular weights Mn and Mw of the PLGA scaffolds for 1, 2 and 3 months were determined by GPC (description of this method and the data evaluation has been added in chapter 2.10). The results obtained were compared with the initial molecular weights and their difference calculated. We have added these results in the support information manuscript in the new Figure S8. From SI Figure S8, it can be concluded that the changes in molecular weight over time support Figure 3 in the main manuscript.
Comments on the Quality of English Language
Minor editing of English language required.
Answer: We thank the reviewer for pointing out this issue. We have carefully checked the English again. Mistakes found have been corrected.
Reviewer 2 Report
This paper talks about the change in scaffold properties with the change in the PLGA concentration used for the electrospinning of scaffolds. The research work described in the manuscript does not have novelty as previously, all these experiments were performed. Here are some major issues that need to be clarified.
Introduction:
1. In lines 72-76, there is a discussion regarding producing electrospun PLGA samples with “optimal properties.” However, the optimal properties of the PLGA sample were not defined. Why is this work necessary?
2. There is no discussion of why porosity, fiber morphology, mechanical properties, and/or surface roughness are important properties of the PLGA scaffold.
3. Why was 1,1,1,3,3,3-hexafluoro-2-propanol selected as the electrospinning solvent? PLGA is soluble in many electrolytic organic solvents. Further, the dielectric constant of the electrospinning solution was mentioned, but the value of this parameter was not defined.
Methods:
1. Why were these polymer concentrations (2%-5wt.%) selected? Polymer concentrations exceeding 5wt.% PLGA is often used in the production of electrospun substrates.
Results/Discussion:
1. While the importance of polymer solution viscosity was analyzed and discussed, the introduction mentioned the importance of the dielectric constant of the electrospinning solution. However, there was no measure of the dielectric constant of the solutions.
2. What was the point of conducting Raman spectroscopy? The starting material was PLGA. Why would the PLGA have changed with increasing polymer concentration?
3. In lines 486-490, the authors suggested that the scaffold made using the 5% solution had the “best” mechanical properties. Why are higher mechanical properties better? Doesn’t “best” depend on the specific application of the scaffold? However, the authors never defined an application for the scaffold or why higher mechanical properties are better than low mechanical properties.
Author Response
This paper talks about the change in scaffold properties with the change in the PLGA concentration used for the electrospinning of scaffolds. The research work described in the manuscript does not have novelty as previously, all these experiments were performed. Here are some major issues that need to be clarified.
General answer: We thank the reviewer very much for reviewing our manuscript and for the useful comments. We revised the manuscript in accordance with your comments. All changes are marked in green in the main manuscript text and the support information manuscript.
Introduction:
Comment 1: In lines 72-76, there is a discussion regarding producing electrospun PLGA samples with “optimal properties.” However, the optimal properties of the PLGA sample were not defined. Why is this work necessary?
Answer 1: We thank the reviewer for this comment and the important question. The optimal properties of PLGA scaffolds are those properties that would allow effective use of such scaffolds for skin tissue regeneration. More details were added in the discussion and conclusion. In this work, the PLGA scaffolds prepared from 4 wt.% electrospinning solution were selected as the scaffolds with optimal properties, which has now been made clearer in the abstract, discussion and conclusion.
Indeed, there are many studies describing the effects of polymer concentration on the various properties of electrospun scaffolds. However, there are some contradictory information in the studies investigating the effects of polymer concentration on the properties of the prepared electrospun scaffolds. The importance of our work is now described in more detail in the introduction.
Comment 2: There is no discussion of why porosity, fiber morphology, mechanical properties, and/or surface roughness are important properties of the PLGA scaffold.
Answer 2: We thank the reviewer for pointing out this issue. In the discussion, information was added to describe in more detail why porosity, fiber diameter, and mechanical properties are important characteristics for the study of PLGA scaffolds.
Comment 3: Why was 1,1,1,3,3,3-hexafluoro-2-propanol selected as the electrospinning solvent? PLGA is soluble in many electrolytic organic solvents. Further, the dielectric constant of the electrospinning solution was mentioned, but the value of this parameter was not defined.
Answer 3: We thank the reviewer for this question. HFIP (1,1,1,3,3-hexafluoro-2-propanol) was chosen because this solvent showed the best results for the prepared PLGA scaffolds, while the other common organic solvents (acetone, chloroform) gave worse results. Moreover, this solvent has already been used in our work on electrospinning PLGA scaffolds, and it has been shown that good quality PLGA fibers can be obtained with HFIP [1,2]. In the introduction, we have deleted words related to the dielectric constant and corrected this sentence.
Methods:
Comment 1: Why were these polymer concentrations (2%-5wt.%) selected? Polymer concentrations exceeding 5wt.% PLGA is often used in the production of electrospun substrates.
Answer 1: We thank the reviewer for this question. In most publications on the production of PLGA scaffolds, spinning solutions with PLGA concentration higher than 5 wt.% are usually used. However, we cannot make PLGA scaffolds from electrospinning solutions with more than 5 wt%, instead a polymer film forms on the collector and the result is no polymer scaffold. This fact is related to the extremely high molecular weight (Mw = 338000 g/mol) of the PLGA used.
Results/Discussion:
Comment 1: While the importance of polymer solution viscosity was analyzed and discussed, the introduction mentioned the importance of the dielectric constant of the electrospinning solution. However, there was no measure of the dielectric constant of the solutions.
Answer 1: We thank the reviewer for this comment. In fact, dielectric constant and viscosity are one of the most important factors affecting the fiber morphology. In the introduction, we have deleted words related to the dielectric constant and corrected this sentence. This was done because in the present work we investigated how polymer concentration affects the properties of PLGA scaffolds. To investigate the influence of dielectric constant, other solvents with different dielectric constant values has been used in another study [3], but in our work we use only one solvent.
Comment 2: What was the point of conducting Raman spectroscopy? The starting material was PLGA. Why would the PLGA have changed with increasing polymer concentration?
Answer 2: We thank the reviewer for these helpful questions. Raman spectroscopy was used to determine that the scaffolds did not contain solvent residues (HFIP). Therefore, the Raman spectra help the reader to conclude that high-purity PLGA scaffolds were prepared. The corresponding sentence was added in chapter 3.3.
Comment 3: In lines 486-490, the authors suggested that the scaffold made using the 5% solution had the “best” mechanical properties. Why are higher mechanical properties better? Doesn’t “best” depend on the specific application of the scaffold? However, the authors never defined an application for the scaffold or why higher mechanical properties are better than low mechanical properties.
Answer 3: We thank the reviewer again for these useful questions. The mechanical properties of electrospun scaffolds are important characteristics that determine their application in tissue engineering. We have rewritten misleading expressions in this context. In the discussion, we added that such scaffolds could be used for soft tissue regeneration, especially for skin tissue regeneration, and that according to the literature, the 4 wt.% PLGA scaffolds have optimal mechanical properties for skin tissue regeneration.
References
[1] Badaraev, A.D.; Lerner, M.I.; Bakina, O. V.; Sidelev, D. V.; Tran, T.-H.; Krinitcyn, M.G.; Malashicheva, A.B.; Cherempey, E.G.; Slepchenko, G.B.; Kozelskaya, A.I.; Rutkowski, S.; Tverdokhlebov, S.I. Antibacterial Activity and Cytocompatibility of Electrospun PLGA Scaffolds Surface-Modified by Pulsed DC Magnetron Co-Sputtering of Copper and Titanium. Pharmaceutics, 2023, 15, 939.
[2] Badaraev, A.D.; Sidelev, D. V.; Kozelskaya, A.I.; Bolbasov, E.N.; Tran, T.-H.; Nashchekin, A. V.; Malashicheva, A.B.; Rutkowski, S.; Tverdokhlebov, S.I. Surface Modification of Electrospun Bioresorbable and Biostable Scaffolds by Pulsed DC Magnetron Sputtering of Titanium for Gingival Tissue Regeneration. Polymers (Basel)., 2022, 14, 4922.
[3] Luo, C.J.; Stride, E.; Edirisinghe, M. Mapping the Influence of Solubility and Dielectric Constant on Electrospinning Polycaprolactone Solutions. Macromolecules, 2012, 45, 4669–4680.
Reviewer 3 Report
The manuscript "Effect of PLGA Concentration in Electrospinning Solution on Biocompatibility, Morphology and Mechanical Properties of Nonwoven Scaffolds" has exciting results. The presentation of the paper is quite good. The authors clearly stated the purpose of their study in the introduction, and they also did a good job of illustrating it. Additionally, the findings support the conclusions. I have no doubt that the paper is accepted for publication.
Moderate editing of the English language is required.
Author Response
The manuscript "Effect of PLGA Concentration in Electrospinning Solution on Biocompatibility, Morphology and Mechanical Properties of Nonwoven Scaffolds" has exciting results. The presentation of the paper is quite good. The authors clearly stated the purpose of their study in the introduction, and they also did a good job of illustrating it. Additionally, the findings support the conclusions. I have no doubt that the paper is accepted for publication.
General answer: We like to thank the reviewer for this judgement and the appreciation of our work. We revised the manuscript in accordance with your comments. All changes are marked in green in the main manuscript text and the support information manuscript.
Comments on the Quality of English Language
Moderate editing of the English language is required.
Answer: We thank the reviewer for this comment. We have carefully checked the English again. Mistakes found have been corrected.
Round 2
Reviewer 2 Report
The paper can be accepted.
