Enhanced Corrosion Resistance and Cytocompatibility of Magnesium Alloys with Mg(OH)2/Polydopamine Composite Coatings for Orthopedic Applications
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper reports a study of a coating process to protect magnesium from corrosion, thereby making it suitable for use in devices for implants in the human body. The use of such coating allows the mechanical properties of magnesium to be exploited without rapid degradation under physiological conditions.
The coating developed and studied is a composite material based on magnesium hydroxide with strontium-containing polydopamine. Experiments compared samples coated with this composite with samples of magnesium oxide and magnesium oxide coated with magnesium hydroxide. Sufficient replicates were tested in each experiment to allow conclusions to be drawn concerning accuracy and repeatability of results.
The findings were that the composite coating was highly stable under experimental conditions, resisting dissolution and remaining crack-free. It inhibited corrosion but allowed a mineralized deposit to form when the samples were exposed to SBF. In vitro studies using cultured osteoblasts showed the coated surface to be highly cyto-compatible, with cells spreading across the surface and remaining viable and firmly attached. Overall, results with this coated magnesium were very promising.
The paper is well written, with only a few corrections needed to the English. There are a few additional corrections needed as well. These are as follows:
Line 29: "help" should be "helps", and "delays" should be "delaying".
Line 50: "achived" should be "achieved".
Line 62. Delete the word "accordingly". Change "arrive" to "achieve".
Line 105: Add more detail of the resin.
Line 149: The word "silastic" is a trade name and should have a capital letter.
Line 164: Replace "diligently" with "carefully".
Line 167: Add a capital letter to "international".
Line 170: Replace "washed" with "washing".
Line 292: Replace "law" with "order".
Line 294: Replace "more excellent" with "better".
Line 301: Replace "are demonstrated" with "demonstrate".
Line 336: Replace "stating" with "showing".
Line 359: Put relevant numbers in place of "ss to xx".
Line 360: Replace "magnitudes" with "magnitude".
Line 362: Replace "outlayer" with "outer layer of".
Line 363" Replace "... period, thus the..." with "period. Overall the...".
Line 364: Replace "little" with "less". Replace "more excellent" with "better".
Line 365: Delete "than Mg(OH)2 coating" at the end of the sentence.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsGeneral comments
The submitted manuscript is focuse don the development and characterisation of a coating system based on a dense Mg(OH)â‚‚ interlayer (MAO/HT) superimposed on the MAO-treated substrate.
The topic is interesting and worthy of investigation, and it perfectly matches with the aim and scope of Coatings. However, some revisions have to be applied.
Specific remarks and suggestions are reported below point by point.
Abstract
- It is too long. Please, properly summarise it.
Introduction
- The Introduction section is well conceived and structured. The aim of the submitted manuscripts has been well highlighted, but the originality and the innovative contribution have to be emphasised, at the end of the Introduction section.
- Materials and Methods
2.1. Sample preparation
- More details about the used reagents, such as the supplier and purity, have to be added.
2.2. Sample characterization
- How were the samples prepared for SEM observation? Please, add details.
2.3. Corrosion resistance evaluation
- More details have to be added. For example, the shape and dimension of the investigated samples and the proportion between the sample and the used volume of SBF:
- Results and discussion
As a general consideration, the Authors should more deeply discuss the acquired data, comparing them with the literature. They well and deeply described them but they partially failed in comparing them with literature.
3.1. Coating character
- For the measurements of the pores diameter, as well as of the thickness, in the related experimental section more details have to be added, such as the used software and the number of considered pores in order to provide an average value.
-For EDS microanalysis, it is very important to take into account that it is not a quantitative characterisation, thus to talk of atomic ratio has no sense. In order to provide information about the chemical composition, other techniques should be exploited.
- For XRD patterns, the used JCPDS card numbers have to be specified both within the body text and the related Figure.
- The following considerations “No significant discrepancies are manifested between the XRD patterns of the MAO/HT and MAO/HT/PDA samples, which could be attributed to the relatively thin layer or amorphous crystallinity of the PDA prepared using this polymerization method” have to be supported with proper literature references.
3.2. Corrosion resistance
The reported considerations have to be compared with the literature.
- Conclusions
- The main numerical data have to be added.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript “Enhanced Corrosion Resistance and Cytocompatibility of Magnesium Alloys with Mg(OH)2/Polydopamine Composite Coatings for Orthopedic Applications” was submitted to Coatings. This work evaluates an important subject: improvement in the use of Mg alloys for implants or other biological/medical applications by measuring and interpreting the corrosion behavior of Mg exposed to SBF media with different post-treatments and surface conditions/properties. The Introduction section presents the importance of this subject and the published literature and state-of-art of post-treated Mg-based materials. Materials and Methods section presents in detail the experiment guaranteeing its reliability. The Results section are clear presented and support the Conclusions listed by the authors. Some minor comments are listed by the reviewer to improve the manuscript quality before its acceptance for publishing.
Page 166: The reviewer recommends “(40, 60, 80, 100%)” instead of “(40%, 60%, 80%, 100%, 100%)”. Besides this, specify if it is vol.% or wt.%.
Page 194: The reviewer recommends simply “HT” instead of “HT treatment”. As it is written, it is redundant.
Page 202: The reviewer recommends reviewing the underscored index for all the chemical formulas, e.g., “MgF2” instead of “MgF2” or “Mg(OH)2” instead of : Mg(OH)2”. Please review the whole manuscript.
Page 217: The reviewer recommends “e (2.51×10–7 A·cm–2)” instead of “e (2.51×10-7 A·cm-2)”
Page 217-218: The reviewer recommends “. This suggests that the MAO/HT/PDA sample exhibits a higher resistance to the corrosion phenomenon in SBF,” instead of “This suggests that the MAO/HT/PDA sample exhibits significantly improved anti-corrosion performance,”
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe Authors have applied all the Referees'suggestions and the paper looks very improved. It can be accepted in the current version.
