Carbonated Hydroxyapatite-Based Honeycomb Scaffold Coatings on a Titanium Alloy for Bone Implant Application—Physicochemical and Mechanical Properties Analysis
Round 1
Reviewer 1 Report
The abstract presents the reader with the promise of an interesting and novel study. Unfortunately, the novelty and the findings are not clearly conveyed in the body of the manuscript, which does need to be amended if this study is to be publishable.
The concept of EPD and dip coating of HA is not novel. It has been in use for decades. The novel aspect to this study is the use of honeycomb. However, in this regard the study is somewhat unclear. Was the purpose of the honeycomb to produce a microporous or macroporus network microstructure in the HA coatings? Was the production of honeycomb macrostructure in the coatings a research objective? If so it receives the most fleeting of references. Figure 5 image a. That is all. Thus one must conclude that the honeycomb issue is a minor issue in this study. Either honeycomb is the central novelty of this study, or it is a peripheral issue of little relevance. Which is it? If the latter, then where is the novelty? Is it the combination of EPD and dip-coating? If so, the results are somewhat unclear in terms of what has been discovered with the EPD/Dip dual coating approach. Dual coating is less novel than honeycomb, but dual coating may be presented in a way to convey novelty, which is not the case in the present manuscript.
In short the objectives are not clear, nor is it at all clear in the results whether the objectives were achieved and if so in what way? The novelty is not clear. The central purpose of the study is not clear. The manuscript needs to be amended to clarify the above issues. This would be a major re-write.
Minor Issues:
- Figure and table captions should unambiguously identify all concepts in the figures. Never leave the reader guessing when trying to make sense of a figure or table. Spell it out unambiguously. For example Figure 6 and Table 4 DO NOT define the attributes of the control at all. Is it a coating? If so under what conditions? Is it simply monolithic HA? Given that the control has better mechanical properties to the experimental coatings, this is of significant importance.
- Methodology 2.2, it is not satisfactory to leave the reader guessing. The synthesis method needs to be described. If it is not original work, then the source of the methodology should be cited, but whether novel or not, it needs to be described. Briefly if necessary, in detail if necessary.
Author Response
Dr. Alessandro Lavacchi
Istituto di Chimica dei Composti OrganoMetallici (ICCOM-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy
Editor-in-chief
Coatings
Prof. Dr.Wei Pan
State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science & Engineering, Tsinghua University, Beijing 100084, China
Editor-in-chief
Coatings
Dr. Wesley Wang
Assistant Editor of Coatings
wesley.wang@mdpi.com
Suite 305, Zhongjia Mansion, Building No.13, Taiyangyuan Community, Dazhongsi
East Road, Haidian District, Beijing 100190, China
MDPI Coatings Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
coatings@mdpi.com
https://www.mdpi.com/journal/coatings 24 July 2021
Dear Dr. Alessandro Lavacchi, Prof. Dr.Wei Pan, Dr. Wasley Wang and Reviewers,
The authors would like to thank and express our appreciation to the editor and reviewers for giving us the opportunity to revise our manuscript. The authors received many constructive recommendations to improve the manuscript. We are pleased to resubmit our new version of the paper titled “Carbonated Hydroxyapatite-Based Honeycomb Scaffold Coatings on Titanium Alloy for Bone Implant ApplicationPhysicochemical and Mechanical Properties Analysis,” by Mona Sari, Nicholas Adi Kristianto, Chotimah, Ika Dewi Ana, and Yusril Yusuf for consideration of publication in Coatings.
Response to Reviewer 1 Comments
Point 1: The abstract presents the reader with the promise of an interesting and novel study. Unfortunately, the novelty and the findings are not clearly conveyed in the body of the manuscript, which does need to be amended if this study is to be publishable. The concept of EPD and dip coating of HA is not novel. It has been in use for decades. The novel aspect to this study is the use of honeycomb. However, in this regard the study is somewhat unclear.
Response 1 : This study has added the honeycomb (HCB) from Indonesia as a biopolymer and porous agent scaffold to carbonated hydroxyapatite (CHA) from abalone mussel shells. The CHA/HCB wax nanocomposite confirms the non-toxicity scaffold as shown in previous research (Sari, et al. 2021). Therefore, the authors try to coat Titanium (Ti) alloy with scaffold CHA/HCB to be CHA/HCB/Ti coatings. The authors have added the purpose of using HCB in this study in the last paragraph of the introduction section on page 4, lines 130-134.
Then, the authors have developed two methods by which to impact the controlling of surface morphology, layer thickness, free cracking, and the formation of a homogeneous layer relatively quickly. The development of the two methods produces in an electrophoretic deposition dip coating (EP2D). This tool combines a series of dip coater devices and EPD tools that were integrated into the computer. This tool is used for the coating process of CHA and the scaffold CHA/HCB to Ti alloy.
Sari, M.; Hening, P.; Chotimah.; Ana, I.D.; Yusuf, Y. Porous structure of bioceramics carbonated hydroxyapatite-based honeycomb scaffold for bone tissue engineering. Mater. Today Commun 2021, 26, 102135.
Point 2: Was the purpose of the honeycomb to produce a microporous or macroporus network microstructure in the HA coatings? Was the production of honeycomb macrostructure in the coatings a research objective? If so it receives the most fleeting of references. Figure 5 image a. That is all. Thus one must conclude that the honeycomb issue is a minor issue in this study.
Response 2: As shown in previous research (Sari, et al. 2021), HCB as a porous agent scaffold produces scaffold CHA/HCB 40 . It had macropore and micropore sizes of 102.02 9.88 and 1.08 0.086 μm, respectively. It also had a porosity of 66.36%. Then, the authors try to coat the Titanium (Ti) alloy with scaffold CHA/HCB to be CHA/HCB/Ti coatings, to know the potential of the scaffold in coating with Ti alloy applications and compared with only CHA/Ti coatings for this study.
Based on these preliminary results, CHA and scaffold CHA/Ti can potentially be applied to coatings with the Ti alloy. In this study, the compressive strength for all immersion time variations for CHA/HCB/Ti coatings was about 54–83 MPa, which was within the normal range of human cancellous bone (0.2–80 MPa). Based on SEM analysis (Figure 10 and Table 6), the thickness value for all samples of CHA/HCB/Coatings was about 71–88 . The thickness obtained was following the thickness parameters required for coating, namely 50–200 μm. As shown in XRD results, the HCB was completely degraded from the scaffold material, so no other diffraction peaks appeared in scaffold CHA/HCB 40 . Therefore, the absence of different phases besides Ti and scaffold CHA/HCB indicated no reaction between them. In addition, the change in the Ti phase transformation occurred at a temperature of 900 so that it affected the scaffold CHA/HCB layer. The analysis of a porous network in the CHA coatings and cell viability assay of samples will be assessed in further research. This suggestion was added in the last paragraph of discussion section on page 18, lines 635–636.
Sari, M.; Hening, P.; Chotimah.; Ana, I.D.; Yusuf, Y. Porous structure of bioceramics carbonated hydroxyapatite-based honeycomb scaffold for bone tissue engineering. Mater. Today Commun 2021, 26, 102135
Point 3: Either honeycomb is the central novelty of this study, or it is a peripheral issue of little relevance. Which is it? If the latter, then where is the novelty? Is it the combination of EPD and dip-coating? If so, the results are somewhat unclear in terms of what has been discovered with the EPD/Dip dual coating approach. Dual coating is less novel than honeycomb, but dual coating may be presented in a way to convey novelty, which is not the case in the present manuscript.
Response 3: The use of HCB for coating CHA/HCB/Ti and the development of the EPD and Dip-Coating method into an electrophoretic deposition dip coating (EP2D) tool integrated into the computer is the novelty of this study. The development of this tool is expected to impact controlling surface morphology, layer thickness, free cracking, and the formation of a homogeneous layer relatively quickly. These results can be seen on layer thickness for CHA/HCB/Ti coatings with immersion times of 10, 20, and 30 min at 71–88 μm. Additionally, the compressive strength for all immersion time variations for CHA/HCB/Ti coatings was about 54–83 MPa, which was within the normal range of human cancellous bone (0.2–80 MPa). The layer thickness and compressive strength that meet the requirements for bone implant applications are obtained quickly. Therefore, it can attain the goal of developing an electrophoretic deposition dip coating (EP2D) tool integrated into the computer and the use of HCB for the CHA/HCB/Ti coating. Overall, the authors have updated the conclusions that support the aims and results of this study on page 19, lines 662–671.
Point 4: In short the objectives are not clear, nor is it at all clear in the results whether the objectives were achieved and if so in what way? The novelty is not clear. The central purpose of the study is not clear.
Response 4: The authors have added the goal of this study, including coating the Ti alloy with the scaffold CHA/HCB to be CHA/HCB/Ti coatings, to know the potential of the scaffold in coating with Ti alloy applications and when compared with only CHA/Ti coatings using EP2D tools that were integrated into the computer developed by the authors.
Minor Issues:
Point 1: Figure and table captions should unambiguously identify all concepts in the figures. Never leave the reader guessing when trying to make sense of a figure or table. Spell it out unambiguously. For example Figure 6 and Table 4 DO NOT define the attributes of the control at all. Is it a coating? If so under what conditions? Is it simply monolithic HA? Given that the control has better mechanical properties to the experimental coatings, this is of significant importance.
Response 1: The authors have added the information about Table 4 (carbonated hydroxyapatite (CHA)/titanium alloy (Ti) coating conditions). Based on Figure 6 and Table 4, the compressive strength value for the control group (Ti alloy) was higher than in the experimental group. This is because during the testing process, the Ti plate coated with CHA and scaffold CHA/HCB 40 was broken after being subjected to pressure from the compressive strength testing tool, so that its compressive strength was reduced. This explanation has been added in the compressive strength results section on page 12, lines 408–411.
Point 2: Methodology 2.2, it is not satisfactory to leave the reader guessing. The synthesis method needs to be described. If it is not original work, then the source of the methodology should be cited, but whether novel or not, it needs to be described. Briefly if necessary, in detail if necessary.
Response 2: The detailed description of the source of the synthesis of CHA has been added in the Materials and Methods section 2.2 on page 5, lines 161–181.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article „Carbonated Hydroxyapatite-based Honeycomb Scaffold Coatings on a Titanium Alloy for Bone Implant Application−Physicochemical and Mechanical Properties Analysis“ of authors Mona Sari, Nicholas Adi Kristianto, Chotimah, Ika Dewi Ana and Yusril Yusuf describes very interesting possibility to cover selected titanium alloy with well-defined carbonated hydroxyapatite layer for possible medical purposes.
The text is written interestingly and it is well organized. It is almost ready for publishing.
Please, correct few typing errors:
- Reference on line 79, please, correct: “sol-gel c”.
- Please, correct on line 140: “NH4OH”
- Line 161, the description of CHA and CHA/HCB solutions: Are you sure that carbonated hydroxyapatite is completely soluble in ethanol, as you mentioned?
- Line 178: “Joel JSM…” or JEOL?
- Line 182: Please, specify mentioned ImageJ software (source or developer, please, add the Reference).
Author Response
Dr. Alessandro Lavacchi
Istituto di Chimica dei Composti OrganoMetallici (ICCOM-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy
Editor-in-chief
Coatings
Prof. Dr.Wei Pan
State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science & Engineering, Tsinghua University, Beijing 100084, China
Editor-in-chief
Coatings
Dr. Wesley Wang
Assistant Editor of Coatings
wesley.wang@mdpi.com
Suite 305, Zhongjia Mansion, Building No.13, Taiyangyuan Community, Dazhongsi
East Road, Haidian District, Beijing 100190, China
MDPI Coatings Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
coatings@mdpi.com
https://www.mdpi.com/journal/coatings 24 July 2021
Dear Dr. Alessandro Lavacchi, Prof. Dr.Wei Pan, Dr. Wasley Wang and Reviewers,
The authors would like to thank and express our appreciation to the editor and reviewers for giving us the opportunity to revise our manuscript. The authors received many constructive recommendations to improve the manuscript. We are pleased to resubmit our new version of the paper titled “Carbonated Hydroxyapatite-Based Honeycomb Scaffold Coatings on Titanium Alloy for Bone Implant ApplicationPhysicochemical and Mechanical Properties Analysis,” by Mona Sari, Nicholas Adi Kristianto, Chotimah, Ika Dewi Ana, and Yusril Yusuf for consideration of publication in Coatings.
Response to Reviewer 2 Comments
The article “Carbonated Hydroxyapatite-based Honeycomb Scaffold Coatings on a Titanium Alloy for Bone Implant Application−Physicochemical and Mechanical Properties Analysis“ of authors Mona Sari, Nicholas Adi Kristianto, Chotimah, Ika Dewi Ana and Yusril Yusuf describes very interesting possibility to cover selected titanium alloy with well-defined carbonated hydroxyapatite layer for possible medical purposes. The text is written interestingly and it is well organized. It is almost ready for publishing. Please, correct few typing errors:
Point 1: Reference on line 79, please, correct: “sol-gel c.”
Response 1: The authors have revised the reference in line 79 to Sol-gel [21] in the Introduction section on page 3, lines 85.
Point 2: Please, correct line 140: “NH4OH”
Response 2: The authors have revised the subscript formatted “NH4OH’ in the Materials and Methods section on page 4, lines 153.
Point 3: Line 161, the description of CHA and CHA/HCB solutions: Are you sure that carbonated hydroxyapatite is completely soluble in ethanol, as you mentioned?
Response 3: Hydroxyapatite (HA) has the ability to act as a catalyst, and it has the unusual property of containing an acidic site and a basic site in a single crystal lattice (Tsuchida, et al. 2008). The stoichiometric HA (Ca10(PO4)6(OH)2) with hexagonal lattice symmetry (P63/m) has structural flexibility. Thus, the HA lattice can undergo considerable distortion by incorporating Ca2+ and PO43- ions of different sizes. Therefore, it is possible to change the acid-base properties of HA by modifying its catalytic activity (Lovon-Quintana et al. 2017). By adding OH- and/or PO43- ions with CO32- anions, carbonated hydroxyapatite (CHA) can be obtained. So, CHA also has the ability to act as a catalyst that can bind acidic materials (ethanol) and alkaline materials (Lovon-Quintana et al. 2017). Thus, CHA is completely soluble in ethanol.
Tsuchida, T.; Kubo, J.; Yoshioka, T.; Sakuma, S.; Takeguchi, T.; Ueda, W. Reaction of ethanol over hydroxyapatite affected by Ca/P ratio of catalyst. Journal of Catalysis 2008, 259, 183-189.
Lovon-Quintana, J.J.; Rodriguez-Guerrero, J.K.; Valenca, P.G. Carbonated Hydroxyapatite as a catalyst for ethanol conversion to hydrocarbon fuels. Applied Catalysis A, Genera; 2017, 542, 136-145.
This description has been added in the Preparation of CHA and scaffold CHA/HCB solutions section on pages 5–6, lines 195–203. The references also have been added by authors in References No. 34 and 35.
Point 4: Line 178: “Joel JSM…” or JEOL?
Response 4: The authors have revised SEM-EDS (Joel JSM-6510LA-1400, Japan) to (Jeol JSM-6510LA-1400, Japan) in the Materials and Methods section on page 6, line 218.
Point 5: Line 182: Please, specify mentioned ImageJ software (source or developer, please, add the Reference).
Response 5: The authors have added the information about ImageJ software, including version, developer, and its reference on page 6, line 222-223. The references also have been added by authors in References No. 36 and 37.
Author Response File: Author Response.docx
Reviewer 3 Report
Dear authors,
the topic of the paper is interesting and highly applicable for the definition of biomaterials that can be used to regenerate skeletal tissue. However, it is obvious that this is just the next manuscript regarding your research line investigation since there can be found a large overlap with your previous manuscripts. However, you are offering new observations and results including (1) synthesis of CHA (carbonated hydroxyapatite) based on abalone mussel shells by applying different stirring times, and (2) coating of Titanium alloy with CHA and CHA/HCB (honeycomb) 40 wt% by electrophoretic deposition dip-coating method applying different immersion times. Besides, the physicochemical characterization/properties and mechanical testing of these systems (materials) are also present/described/discussed.
There are some of my comments/suggestions/questions:
The introduction is written very well and clearly. However, it was quite difficult to follow and understand the part with the presented results and their interpretation (Discussion). I think it can be improved.
I recommend improving the quality of some figures (for example, Figure 1) as well as reevaluating the number of the figures and tables presented in the manuscript. It seems to be duplicity repeated the same information without any additional benefit. You can join together some of them and thus conclude the obtained results by more readily way. For example, information from Table 1 can be included in Figure 2. The same for Table 4 and Figure 6; Table 6 and Figures 9 and 10.
Figure 2, 4 and 5: Please, correct the legend (remove or add what is needed).
Figure 3: Please, define (in the Materials and Methods part) what spectral resolution did you have. / Wave Number (cm-1) should be written as one word (Wavenumber (cm-1)). This one is also in Figure 5.
Figure 5: The pores indicated by the white arrows are those which are important/in which you are interested - which size is reported in Table 3?
Figures 7 and 8: Please, use the same x-axis scale.
Table 2: How did you estimate the Ca and P (%) content?
Table 3 and 5: What I the "S"? Is it a crystallite size? Please, define it.
Please, write discuss firstly and just then add the discussed values (this is the case of Table 3).
Figures 9 and 10: The zoomed areas should be even more zoomed. It is not clear how are you measuring the thickness of the coating (from which point to which point) - there is no clear rule to define the coating layer, isn't it?
ImageJ software should be cited.
Pg. 8: "In this study, CHA with a stirring time of 45 min was demonstrated to be the best bioceramic material by its morphology, particle size distribution and composition characteristics." + " The physicochemical analysis of CHA with a stirring time of 45 min shows that it can be applied in coating processes for bone implant applications." It is not clear to me how you have deduced that this one is the best and that it can be used for coating.
Figure 5: Can I imagine that we have areas with macropore structure and areas with micropore structure or are they both mixed together in some manner?
Why "the middle experiments" (30 min-stirring times and 20 min-immersion times) are so different (out of the observed tendencies)?
Pg. 16: "...CHA with a stirring time of 45 min displayed the OH- stretching mode, which is supported by FTIR data [33]. Therefore, it has potential for coating on Ti alloy applications." Why?
Besides, bands corresponding to the OH-stretching vibrations can be observed in all FT-IR spectra presented in the manuscript.
Please, check spaces, dots, upper indexes, etc. through the text of the manuscript.
Concluding, I recommend the manuscript after a minor revision/modification for its publication in Coatings.
Round 2
Reviewer 1 Report
The authors have satisfactorily addressed my concerns raised in my first review. The manuscript is now acceptable for publication.
