Atmospheric-Pressure Plasma Jet-Induced Graft Polymerization of Composite Hydrogel on 3D-Printed Polymer Surfaces for Biomedical Application

Round 1

Reviewer 1 Report

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Author Response

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Reviewer 2 Report

Abstract is clear and defines in a timely manner the contribution and relevance of the study proposed by the authors.

The state of the art is broad and current, where it is described what refers to the subject of study, identifying the parts of relevance or necessary knowledge, to guide and define the line of research of interest.

Methodology is adequately described, the method is defined.

Section 3.1. It is advisable to expand discussion, supporting with adequate scientific literature, for example, in relation to why the APPJ treated in argon improves the hydrophilic character of PLA (3D), it is indicated that this can be attributed to the incorporation of groups containing oxygen, expand and support in this regard. Likewise, it is indicated that the longer the plasma treatment time and the more HEMA content, the more pronounced the hydrophilicity. Why? Detail with scientific support if possible.

Section 3.2. FTIR studies are described in a general way, making the respective assignments attributed to stretching and vibrations of certain functional groups present in the materials studied. It is mentioned in the analysis that there is a change in the intensity of the absorption peaks due to the incorporation of polar functional groups containing oxygen on the surface of samples, in this sense, perhaps it could be correlated with the results and comments indicated in the contact angle study, where such oxygen seems to be of interest.

Text in Figure 2, can be improved... It looks a little blurry.

Figure 3, improve, no text, scale..... I think you could increase the size of the micrographs. To appreciate details of interest.

Section 3.3, the discussion can be improved. It is indicated that morphologies are shown, but by the scale it is not clear what is indicated, for example it is said that there are smooth surfaces, others that have pores, but this assignment is not clear. Perhaps some study using some software to find roughness, to do cross-sectional analysis, might be appropriate. In the same way, correlating with contact angle study would be interesting. Support with literature the comparison of organizations of the samples (for example coral).

Text in figure 4, can be improved. It's blurry.

Degradation of the material is interesting, was contact angle study performed after having degraded material?

Conclusions can be improved, after expanding analysis of results and correlating the various results.

Author Response

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Reviewer 3 Report

At the moment, polylactic acid, often known as PLA, is the substance that sees the greatest use in 3D printing. Polylactic acid has favorable mechanical qualities, chemical stability, and biodegradability; nevertheless, the surface of the acid is hydrophobic, which prevents it from being used to its full potential. The development and metabolism of ground attachment, as well as methods to boost the strength of PLA with high brittleness, have long been subjects of investigation by scientists. Additionally, 3D printing PLA materials for use in the biomedical area has also been a focus of study. In this study, the authors made the structures using the Fused Filament Fabrication (FFF) method. To begin, the surfaces of the 3D-printed polymers were subjected to treatment with an atmospheric-pressure plasma jet (APPJ) in order to increase the amount of polar functional groups on the surface and make the surface hydrophilic. After that, a UV photo-grafting polymerization of 2-Hydroxy-ethyl methacrylate (HEMA), poly(ethylene glycol) methacrylate (PEGMA), and hydroxyapatite (HAp) was placed onto the surfaces of the 3D printed polymers. The experimental findings of the water contact angle for the wettability test demonstrate that APPJ-treated and UV-graft composite hydrogel become hydrophilic in order to effectively activate the 3D-printed polymer surface. In the in vitro investigation, the impact of APPJ treated and composite hydrogel on the viability of osteoblast-like MG63 cells was investigated using the Alamar Blue cell viability test. The results indicate that biocompatibility was enhanced for the composite hydrogels. It is anticipated that the proposed technique will have promise in the use of bone scaffolds in the years to come.

The proposed work is very interesting. However, the following modifications must be carried out by the authors before the manuscript can be published.

1.       The quality of Figure 4 is very poor. A high-resolution figure should be included.

2.       The standard deviations in Figure 4 have not been provided. The authors should perform the experiment at least twice and represent the results as mean ± SD.

3.       The statistical analysis of the swelling studies should be conducted using the swelling data at the end of the experiment.

4.       SEM/ ESEM/ CLSM microscopic images of the cytocompatibility test should be provided.

5.       MTT assay should be conducted to establish the biocompatibility of the materials.

Author Response

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Reviewer 4 Report

The research aims to make the surface of polylactic acid objects made by 3D printing and intended for biomedical applications hydrophilic.

For this, the authors considered a surface treatment of PLA products with atmospheric pressure plasma jet to make their surface hydrophilic and the subsequent deposition on it of an acrylic composite hydrogel by UV-grafting.

The hydrophilicity of the new surfaces was verified with contact angle measurements while in vitro tests assured the viability of MG63 cells on them.

Very interesting work given the extensive use of polylactic acid for the production of 3D printed items. The manuscript is well articulated and appreciable is the scientific relevance of the contents.

However, some revisions are necessary to improve the understanding of the contents and ensure the effective transfer of the acquired know-how also to readers less familiar with the biomedical aspects covered.

Specifically, MINOR REVISIONS are recommended to make the following corrections:

Lines 9-11: the sentence starting with “The growth…” is not clear. Please rephrase.

Line 43: The last part of the sentence “and 3D printing technology” must be deleted. Here are some biomedical applications of the technology. What was meant?

Line 71: it is written “it has growth capacity”. It is unclear what the authors mean. Please explain in more detail.

Line 95: Please delete the final word "research" before citations 39-40, to avoid cacophonous repetitions.

Line 97: At the end of the sentence ending with the word “biomedical”, it is recommended to add the word “applications”.

Line 168: What is meant by "dry treatment composite hydrogel"? Please explain.

Line 189: Here it is written “…treatment 3D printed PLA…” but probably the authors meant to write “…treated 3D printed PLA…”. True?

Lines 207-209: This sentence is poorly constructed and incomprehensible. Please rephrase.

Line 211: It is recommended to replace “…which can be attributed to…” with “…favouring…”.

Lines 211-212: It is suggested to replace “…the 3D printed PLA samples…” with the word “…their…” to avoid repetitions.

Line 213: Please replace “…grafting…” with “…grafted…”

Line 239: It is written “hydrogel hydrogels”. Please remove repetitions.

Lines 250-251: Probably, the sentence starting with “However” is incomplete. Please check.

Line 275: The word “after” is usefulness. Please cancel it.

Lines 297-298: The sentence is incomplete. Perhaps the last part of the sentence is “the lower degradability of the hydrogel occurs when it contains more PEGMA”

Lines 303-304: The sentence starting with “the in vitro cytocompatibility…” is incomplete. Please check.

Line 305: About the sentence starts with “Conditions…”, it is not clear what authors meant. Please check.

Line 308: It is suggested to start the sentence as “In Fig. 5, a and b, …”

Overall, the work is relevant but a careful re-reading of the text is recommended, perhaps even with the help of an English-speaking colleague.

Author Response

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Round 2

Reviewer 3 Report

May be accepted