Preparation and Characterization of Sustained-Release Naringin Coating on Magnesium Surface
Round 1
Reviewer 1 Report
The manuscript under the title: “Preparation and characterization of a micro-arc oxidation coating with sustained-release naringin on a pure magnesium surface” is relevant for the Coatings journal. The authors work on up-to-date topic connected with magnesium materials and their coatings. The article based on original experimental research. The organization of the article is appropriate. The abstract is very informative. Overall, the paper is well prepared, but there are needed small improvements, in order to be published:
- Please add in the introduction some aspects related to the influence of additional elements of Mg- alloys, regarding the corrosion resistance and microstructural aspects
- Please add the ICDD files for all XRD compounds detected
- Please update the conclusions with more experimental values.
Author Response
Dear Editors and Reviewers:
Thank you for your letter and for the reviewers’comments concerning our manuscript entitled “Preparation and characterization of a micro-arc oxidation coating with sustained-release naringin on a pure magnesium surface” (coatings-1106960). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:
Point 1: Please add in the introduction some aspects related to the influence of additional elements of Mg- alloys, regarding the corrosion resistance and microstructural aspects.
Response 1: Thank you for your suggestion. We have rewritten the introduction part as follow.
However, the low potential of magnesium and its alloys leads to excessive degradation in the physiological environment, and the pH rises around the implant, resulting in unmanageable air cavity, inflammation, infection and other complications, which cannot meet the requirements of implant materials in vivo [9-13], thereby reducing the biological safety and compatibility of implant materials. Therefore, in order to improve the degradation rate of magnesium-based materials, match the rate of bone healing and ensure its good biocompatibility. At present, the degradation rate of magnesium and its alloys is mainly through the alloying and surface modification of magnesium. T. Rzycho´ n have develop WE43 alloy stents and screws, which has been successfully applied in the human body [14]. Yan treated AZ31B magnesium alloy with fluorine, and the fluoride conversion coating obtained significantly improved the corrosion resistance of AZ31B, and the degradation performance of AZ31B after fluoride treatment could meet the requirements of biodegradable materials [15]. Yan on AZ31B magnesium alloy The prepared rare earth conversion coating has good corrosion resistance and good anticoagulant performance [16]. Lu is prepared by chemical deposition and micro-arc oxidation treatment on the surface of magnesium to prepare biologically active strontium containing Ca-P coating (Sr-Ca-P MAO), can significantly reduce the corrosion rate of pure magnesium, and show better biomineralization characteristics [17].
[15] Yan, T.; Tan, L.; Xiong, D.; Liu, X.; Ke, Y. Fluoride treatment and in vitro corrosion behavior of an AZ31B magnesium alloy[J]. Materials Science and Engineering C, 2010, 30(5): 740-748. [CrossRef]
[16] Yan, T.; Tan, L.; Xiong, D.; Zhang, B.; Yang, K. A manganese oxide contained coating forbiodegradable AZ31B magnesium alloy[J]. Surface Review and Letters, 2009, 16(4): 533-538. [CrossRef]
[17] Lu, Y.; Wan, P.; Tan, L.; Yang, K. Lin, J. Preliminary study on a bioactive Sr containing Ca-P coating on pure magnesium by a two-step procedure[J]. Surface and Coatings Technology, 2014, 252(9): 79-86. [CrossRef]
Point 2: Please add the ICDD files for all XRD compounds detected.
Response 2: We are very sorry for the missing in this regard, and relevant data has been added in the manuscript, as follows:
The phase structures of the various coatings were characterized by XRD, as shown in Figure 1. The UMAO coating mainly consisted of MgO (ICDD file no. 65-0476) and Mg2SiO4 (ICDD file no. 83-1807) phase [24-25]. MgO and Mg2SiO4 phase were detected UMAO/PLGA/NG coatings. In addition, due to the thin film, the Mg phase was detected in various coatings (ICDD file no. 35-0821).
[24]Batra, U.; Kapoor, S.; Sharma, S. Influence of Magnesium Ion Substitution on Structura land Thermal Behavior of Nanodimensional Hydroxyapatite. J. Mater. Eng. Perform. 2013, 22, 1798-1806. [CrossRef]
[25]Diana, M.V.; Ionut, C.I.; Elena, U. Magnesium Doped Hydroxyapatite-Based Coatings Obtained by Pulsed Galvanostatic Electrochemical Deposition with Adjustable Electrochemical Behavior. Coatings 2020, 10, 2-17. [CrossRef]
Point 3: Please update the conclusions with more experimental values.
Response 3: Thank you for your suggestion. We have added the data of result in the manuscript, and re-written this part according to the Reviewer’s suggestion.
Three coatings (UMAO, UMAO/PLGA and UMAO/PLGA/NG) were prepared in this experiment, and the morphology, composition, corrosion behavior and biological activity of the coatings were studied. XRD results showed that the three coatings were composed of Mg, MgO, and Mg2SiO4. XPS results showed that when the NG was added to the PLGA coating, it was primarily associated with the PLGA in the form of an ester bond or dehydrated into a bond when forming the coating, resulting in a stable coating. After SBF soaking, UMAO/PLGA/NG coating formed more hydroxyapatite. The electrochemical results showed that the corrosion current of the UMAO/PLGA/NG coating was 3.6 × 10-8, which was two orders of magnitude lower than that of the UMAO coating, indicating that the coating had better corrosion resistance. The drug was sustained in vitro for up to 20 days. Compared with UMAO and UMAO/PLGA coatings, UMAO/PLGA/NG coating had better corrosion resistance and bioactivity. This development of biological functionalization has many potential applications.
Once again, thank you very much for your constructive comments and suggestions which would help us both in English and in depth to improve the quality of the paper.
Kind regards,
Liting Mu
E-mail: muliting@163.com
Corresponding author:
Zhen Ma
E-mail address: mz252930179@163.com
Muqin Li
E-mail address: jmsdxlimuqin@163.com
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this paper, Mg samples with a ceramic coating produced by UMAO with further treatments in PLGA and NG have been prepared and examined by suitable structural and electrochemical techniques to test their corrosion resistance and biological activity. The experimental results are interesting, which support the conclusions given. The paper is well structured. However, there are several points requiring attention:
1) The authors claim that few reports deal with PLGA combined with naringin (lines 79-81). However, no references to previous works are given. The authors should clearly explain the conclusions achieved in such previous works and how the present paper represents a new contribution.
2) In the experimental part, line 87, it is indicated that 15 mm x 15 mm x 1mm Mg cubes have been used to prepare the test samples. Are they cubes or foils?
3) Also, in the experimental part, more details about the conditions in which the analyses were performed should be indicated. How were the XPS spectra calibrated? In the Electrochemical Tests (no Text), how were the linear sweep voltammograms obtained? Were they performed in a three-electrode cell? Volume? Electrodes? How the anodic and cathodic limits were selected? And the sweep rate? SBF has been indicated as the test solution. However, more details about it should be given. What is the oxidant in this case? Were the EIS experiments performed at open circuit? In section 2.2.4, the analyzed species should be indicated.
4) Lines 130-136. The assignation of the diffraction peaks in XRD should be based on previous references (missing in the paper). Thee-decimal accuracy in these values is questionable.
5) The assignation of chemical species to XPS binding energies should also be based on previous results in the literature (references missing). Two decimal numbers are given in some case. Are they confident?
6) The binding energies in the XPS results have been related to different functional groups of PLGA and NG. However, in a scientific paper, more details about the molecular structure and possible reactivity between PLGA and NG should be given to be related to the corresponding spectra.
7) The deconvolution of the high-resolution spectra shown in the different plots of Fig. 3c-f should be improved because the base line on the right in all of them is well over the experimental data.
8) Fig. 5. The Tafel plots should be represented on the figure and the corresponding values should be listed.
9) The corrosion potential values in Table 2 seem to be obtained from the polarization curves of Fig. 5. However, did they coincide with the open circuit values? This should be linked to the EIS measurements. Were they obtained at these potential values? The potential should be referred to a reference electrode!
10) How was the error of Ecor in Table 2 determined? Repetitive experiments? And the error in Icor? The number of decimals in the error should not exceed those of the given values (i.e. 0.02 for 2.53).
11) The EIS results are very dependent on the coating. This is nice. The experimental values have been fitted to the equivalent circuit in Fig. 6d. It is important to report evidences about the use of such an equivalent circuit (literature references missing).
Author Response
Dear Editors and Reviewers:
Thank you for your letter and for the reviewers’comments concerning our manuscript entitled “Preparation and characterization of a micro-arc oxidation coating with sustained-release naringin on a pure magnesium surface” (coatings-1106960). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:
Point 1: The authors claim that few reports deal with PLGA combined with naringin (lines 79-81). However, no references to previous works are given. The authors should clearly explain the conclusions achieved in such previous works and how the present paper represents a new contribution.
.Response 1: Thank you for your suggestion. We have rewritten this part as follow.
Polylactic acid/glycolic acid copolymer (PLGA) has drawn wide interest as a drug delivery and corrosion-resistant material for orthopedic applications because of several material properties. First of all the PLGA is non-toxic and strong hydrophobicity [21-23]. In addition, adjustable degradation performance and biocompatibility. Li prepared a PLGA coating on the surface of a magnesium-zinc alloy, and evaluated the corrosion resistance of the coating using electrochemical impedance spectroscopy and polarization curves. The results showed that PLGA coating improves the corrosion resistance of Mg-Zn alloy [24].Zeng prepared a Nanosilver/PLGA coating, In vitro and in vivo, the analysis of bacterial colonization and three-dimensional computed tomography scanning analysis. The research indicates that NSPTi implants have simultaneous antimicrobial and osteoinductive activities [25]. Naringin (NG) has unique biological and pharmacological activities, which can promote the growth of osteoblasts, reduce inflammation, and regulate the differentiation and biological activity of osteoblasts. Cai found that NG could increase the bone mineral density and mechanical properties of the femur of ovariectomized osteoporotic rats, and improved the microstructure of trabecular bone [26].Nilamber proved through experiments that topical NG had a protective effect on cell apoptosis. NG could inhibit the absorption of bone by osteoclasts and reduce inflammation; it could promote the proliferation of endothelial progenitor cells and was beneficial to wound recovery [27]. However，few reports focused on the use of PLGA combined with naringin to form a composite sustained-release drug coating to enhance the biological activity and corrosion resistance of magnesium alloys. In this study, the PLGA sustained-release NG drug coating was prepared on the UMAO pure magnesium coating by the self-assembly method, and the structural characteristics, corrosion resistance and biological activity of the composite coating were systematically evaluated. [21] He, F.P.; Chen, Y.; Li, J.Y.; Lin, B.M.; Yi, O.Y. Improving bone repair of femoral and radial defects in rabbit by incorporating PRP into PLGA/CPC composite scaffold with unidirectional pore structure. Journal of Biomedical Materials Research Part A, 2015;103:1312-1324. [CrossRef]
[22]Dan, M.; Dong, L.; Ying, W. Effects of adding resorbable chitosan microspheres to calcium phosphate cements for bone regeneration. Materials Science&Engineering C, 2015;47:266-276. [CrossRef]
[23]Huang, J.G.; Pang, L.; Chen, Z.R.; Tan, X.P. Dual-delivery of vancomycin and icariin from an injectable calcium phosphate cement-release system for controlling infection and improving bone healing. Molecular Medicine Reports, 2013;8:1221-1232. [CrossRef]
[24]Li, J.N.; Cao, P.; Zhang, X.N. In Vitro Degradation and Cell Attachment of a PLGA Coated Biodegradable Mg-6Zn based Alloy. J Mater Sci, 2010, 45(22): 6038-6045. [CrossRef]
[25]Zeng, X.; Xiong, S.; Zhuo, S.; Liu, C.; Miao, J.; Liu, D.; Wang, H.; Zhang, Y.; Zheng, Z.; Ting, K.; Wang, C.; Liu, Y. Nanosilver/poly (dl-lactic-co-glycolic acid) on titanium implant surfaces for the enhancement of antibacterial properties and osteoinductivity. Int J Nanomedicine. 2019;14:1849-1863. [CrossRef]
[26]Cai, Y.L.; Zhang, X.C. Protective effect of Rhizoma Drynariae extract on osteoporosis in ovariectomized rat model. Trop J Pharm Res, 2016, 15(7): 1447-1449. [CrossRef]
[27]NilamberLal, Das.R.; Muruhan, S.; Nagarajan, R.P Naringin prevents ultraviolet-Bradiation-induced oxidative damage and inflammation through activation of peroxisome proliferator-activated receptor γ in mouseembryonic fibroblast (NIH-3T3) cells. J Biochem Mol Toxicol, 2019, 33(3): 2263-2273. [CrossRef]
Point 2: In the experimental part, line 87, it is indicated that 15 mm x 15 mm x 1mm Mg cubes have been used to prepare the test samples. Are they cubes or foils?
Response 2: Magnesium cube with length and width of 15 mm and thickness of 1 mm.
Point 3: Also, in the experimental part, more details about the conditions in which the analyses were performed should be indicated. How were the XPS spectra calibrated? In the Electrochemical Tests (no Text), how were the linear sweep voltammograms obtained? Were they performed in a three-electrode cell? Volume? Electrodes? How the anodic and cathodic limits were selected? And the sweep rate? SBF has been indicated as the test solution. However, more details about it should be given. What is the oxidant in this case? Were the EIS experiments performed at open circuit? In section 2.2.4, the analyzed species should be indicated.
Response 3: Thank you for your suggestion.We have re-written these parts according to the Reviewer’s suggestion as follow.
(1) X-ray photoelectron spectroscopy (XPS, ESCALAB250XI, Thermo Fisher Scientific, Waltham, MA, USA) was used to determine the element surface adsorption, energy band structure, chemical structures of the atoms and molecules, and chemical bonding. The excitation source was Al K α , the test power was 300 W, and C1s (binding energy 284.8 eV) was used before the test to correct the charge displacement of each element in the test. For the XPS peak, software was used to fit the peaks of the high-resolution XPS spectra of the corrected elements.
(2) We are very sorry for our incorrect writing. The manuscript has been rewritten as “tests”.
(3) The linear sweep voltammograms were obtained by the dynamic potential method test. Change the abscissa in Figure 5 to Potential(V).
(4) A three-electrode cell with a working electrode (the coated sample with an exposed area of 1cm2), Pt as a counter electrode, and a saturated calomel electrode (SCE) was used as a reference, the sample as the working electrode, and the open circuit potential is tested. The frequency of the electrochemical impedance spectroscopy (EIS) measurement ranged from 104 to 10−1 Hz. The po-tentiodynamic polarization tests were performed at a scanning rate of 1 mV/s from –500mV to 500mV.
The EIS measurement data werefitted and analyzed with ZsimpWin software.
(5) SBF [28] composition is showed in Table 1. The substance in the simulated body fluid acts as an oxidant to corrode the surface of the specimen.
Table 1. Chemical composition and reagents grade and purity used for preparation of SBF.
|
No. |
Chemical Formula |
Amount |
Reagent Grade |
Purity |
Manufacturer |
|
1 |
NaCl |
8.035 g/L |
ACS reagent |
≥99.90% |
Comeo Co., Ltd.,Tianjin,China
|
|
2 |
NaHCO3 |
0.355 g/L |
Bio Reagent |
≥99.50% |
|
|
3 |
KCl |
0.225 g/L |
ACS reagent |
≥99.50% |
|
|
4 |
K2HPO4•3H2O |
0.231 g/L |
ACS reagent |
≥99.90% |
|
|
5 |
MgCl2•6H2O |
0.311 g/L |
ACS reagent |
≥98.00% |
|
|
6 |
1.0M-HCl |
39 mL |
ACS reagent |
≥37.00% |
|
|
7 |
CaCl2 |
0.292 g/L |
ACS reagent |
≥99.90% |
|
|
8 |
Na2SO4 |
0.072 g/L |
ACS reagent |
≥99.90% |
|
|
9 |
(CH2OH)3CNH2 |
6.118 g/L |
Standard& Buffer |
≥99.90% |
[28]Cui, L.Y.; Gao, S.D.; Li, P.P.; Zeng, R.C.; Zhang, F.; Li, S.Q. Corrosion resistance of a self-healing micro-arc oxidation/poly methyltrimeth oxysilane composite coating on magnesium alloy az31. Corros Sci. 2017, 118, 84-95. [CrossRef]
(6) The drug release concentration was tested by high-performance liquid chromatograph (Agilent 1200, USA) using the following conditions: the column was an Agilent SB-C18 (250 × 4.6 mm, 5 μm, Agilent Technologies, Inc.); the mobile phase was methanol-0.1 % acetic acid water (50:50); and the detection wavelength was 283 nm. Detect the NG content of UMAO/PLGA/NG coating in SBF solution.
Point 4: Lines 130-136. The assignation of the diffraction peaks in XRD should be based on previous references (missing in the paper). Thee-decimal accuracy in these values is questionable.
Response 4: We are very sorry for the missing in this regard, and relevant data has been added in the manuscript, as follows:
The phase structures of the various coatings were characterized by XRD, as shown in Figure 1. The UMAO coating mainly consisted of MgO (ICDD file no. 65-0476) and Mg2SiO4 (ICDD file no. 83-1807) phase [24-25]. MgO and Mg2SiO4 phase were detected UMAO/PLGA/NG coatings. In addition, due to the thin film, the Mg phase was detected in various coatings (ICDD file no. 35-0821).
[24]Batra, U.; Kapoor, S.; Sharma, S. Influence of Magnesium Ion Substitution on Structura land Thermal Behavior of Nanodimensional Hydroxyapatite. J. Mater. Eng. Perform. 2013, 22, 1798-1806. [CrossRef]
[25]Diana, M.V.; Ionut, C.I.; Elena, U. Magnesium Doped Hydroxyapatite-Based Coatings Obtained by Pulsed Galvanostatic Electrochemical Deposition with Adjustable Electrochemical Behavior. Coatings 2020, 10, 2-17. [CrossRef]
Point 5: The assignation of chemical species to XPS binding energies should also be based on previous results in the literature (references missing). Two decimal numbers are given in some case. Are they confident?
Response 5: Thank you for your suggestion. We have added the references and Corrected data of result in the manuscript, and re-written this part according to the Reviewer’s suggestion as follow.
The binding energy of Mg 1s in the UMAO coating was approximately 1303.7 eV, which corresponds to the existence of Mg (1303.9 eV) and MgO (1304.9 eV) in the coating. Figure 4(c) shows the O 1s XPS pattern for the UMAO coating, in which the MgO was present at a binding energy of 531.6 eV and the formation of Mg2SiO4 was confirmed at 536.6 Ev [37]. For Si 2p, the spectrum contained two Mg2SiO4 peaks: one at 101.9 eV for α-Mg2SiO4, and the other at 102.5 eV for γ-Mg2SiO4 [38]. Figure 4(e), (f), and (g) illustrate the C 1s, O 1s, and Si 2p XPS spectra for the PLGA coating, respectively. In Figure 4(e), the fitted peaks that appear at 284.5, 284.6, 285.2, 286.8, 287.1, and 289.1 eV correspond to the C=C, C-H, C-C, C=O, C-O, and COOR functional groups, respectively. This is consistent with the structure of carbon present in PLGA [39,40]. In Figure 4(f), the O 1s pattern of the PLGA coating is fitted to 3 peaks that correspond to -OH (531.9 eV), C-O (532.7 eV), and O-C=O (533.2 eV), indicating the formation of a PLGA coating [41,42]. Figure 4(g) illustrates the Si 2p XPS spectra of the PLGA coating. Because the surface is covered with the PLGA coating, the binding energy intensity of the Si 2p XPS spectrum is very low. Figure 4(h) and (i) show the XPS spectra of C 1s and O 1s in the UMAO/PLGA/NG coating. No Si 2p absorption peaks were seen (Figure 4(a)), and therefore they are not listed. The C 1s spectrum exhibited six peaks for C=C (284.5 eV), C-H (284.6 eV), C=C (285.2 eV), C=O (286.8 eV), C-O (287.0 eV), and RO-C=O (286.4 eV) [39,40]. In Figure 4(i), the O 1s spectrum exhibits three peaks for -OH (531.9 eV), C-O (532.5 eV), and O-C=O (533.6 eV) [41,42].
[37]Lin, X.; Tan, L.; Wan, P.; Yu, X.; Yang, K.; Hu, Z.; Li, Y.; Li, W. Characterization of micro-arc oxidation coating post-treated by hydrofluoric acid on biodegradable ZK60 magnesium alloy. Surf Coat Technol 2013;232:899-905. [CrossRef]
[38] Taheri, M.; Kish, J.R.; Birbilis, N. Towards a physical description for the origin of enhanced catalytic activity of corroding magnesium surfaces. Electrochim Acta, 2014, 116: 396-403. [CrossRef]
[39] Liu, H.; Li, W.L.; Luo, B.H.; Chen, X.; Wei, W.; Zhou, C. Icariin immobilized electrospinning poly(L-lactide) fibrous membranes via polydopamine adhesive coating with enhanced cytocompatibility and osteogenic activity. Materials Science and Engineering C, 2017, 79: 399-409. [CrossRef]
[40] Pozzo, L.Y.; Conceição, T.F.; Spinelli, A. Chitosan coatings crosslinked with genipin for corrosion protection of AZ31 magnesium alloy sheets. Carbohydrate Polymers, 2018, 181: 71-77.[CrossRef]
[41] Vaz, J.M.; Taketa, T.B.; Hernandez, M. J. Antibacterial properties of chitosan-based coatings are affected by spacer-length and molecular weight[J]. Applied Surface Science, 2018, 445: 478-487. [CrossRef]
[42] Mousa, H.M.;Lee, D.H.; Park, C.H. A novel simple strategy for in situ deposition of apatite layer on AZ31B magnesium alloy for bone tissue regeneration. Appl. Surf. Sci, 2015, 351: 55-65.[CrossRef]
Point 6: The binding energies in the XPS results have been related to different functional groups of PLGA and NG. However, in a scientific paper, more details about the molecular structure and possible reactivity between PLGA and NG should be given to be related to the corresponding spectra.
Response 6: Thank you for your suggestion. We have added infrared spectra to the experimental methods and experimental results.
2.2.1 Phase structure of the coating
Fourier transform infrared (FTIR) (VECTOR33, Germany) spectroscopy in the range of 400–4000 cm−1 was used to analyze the surface characteristics of the coatings.
The FT-IR spectra of the various coatings are shown in Figure 2. In the FT-IR spectra of all of the coatings, the band at 424 cm−1 is ascribed to Mg-O stretching vibrations [31]. Also, the SiO42− band appears at 903 and 1022 cm−1 [32]. In the infrared spectrum curve of the UMAO/PLGA coating, PLGA showed three characteristic bands [33].The C-H vibration peak is displayed at 520 cm-1, and the non-stretching vibration peak of the C=O bond is displayed at 1778 cm-1, at 3702 cm-1 is the result of the left shift of the hydroxyl stretching vibration peak in the PLGA structure molecule [34]. The broad and strong absorption peak at 3420 cm-1, which is the stretching vibration peak of -OH, the stretching vibration peak of the carbonyl group at 1580 cm-1, and the absorption peak at 1370 cm-1 is the benzene ring skeleton and the benzene ring. Double bond, the absorption peak at 1150 cm-1 is supposed to be the structure of C-O-C [35, 36].
Figure 2. FT-IR spectra of various coatings.
[31]Hofmeister, A.M.; Keppel, E.; Speck, A.K. Absorption and reflection infrared spectra of MgO and other diatomic compounds. Mon Not R Astron Soc 2003;345:16-38. [CrossRef]
[32]Kharaziha, M.; Fathi, M.H. Synthesis and characterization of bioactive forsterite na-nopowder. Ceram Int 2009;35:2449-54. [CrossRef]
[33]Liu, J.; Lu, J.F.; Kan, J.Jin, C.H. Preparation, characterization and antioxidant activity of phenolic acids grafted carboxymethyl chitosan. International Journal of Biological Macromolecules, 2013, 62, 85-93. [CrossRef]
[34]Cheng S, Wei DQ, Zhou Y. Mechanical and corrosion resistance of hydrophilicsphene/titania composite coatings on titanium and deposition and release of cefa-zolin sodium/chitosan films. Appl Surf Sci 2011;257:2657-64. [CrossRef]
[35] Prabhu, K.; Karar, P.K.; Hemalatha, S. Isolation of chlorogenic acid from the stems of Viburnum coriaceum Blume. Der Pharmacia Sinica, 2011, 2: 87-92. [CrossRef]
[36] Cheng, Z.J; Zhang, L.; Zhao, H.M. Spectroscopic Investigation of the Interactions of Cryptotanshinone and Icariin with Two Serum Albumins. J Solution Chem, 2013, 42: 1238-1262. [CrossRef]
Point 7: The deconvolution of the high-resolution spectra shown in the different plots of Fig. 3c-f should be improved because the base line on the right in all of them is well over the experimental data.
Response 7: Thank you for your suggestion. According to your suggestion, the data has been refitted, the Figure is as follows.
Figure 4. (a) XPS survey spectrum of the different coatings; (b, c, d) detailed XPS spectra of the Mg 1s, O 1s, and Si 2p regions for the UMAO coating, respectively; (e, f, g) detailed XPS spectra of the C 1s, O 1s and Si 2p regions for the UMAO/PLGA coating, respectively; and (h, i) detailed XPS spectra of the C 1s and O 1s regions for the UMAO/PLGA/NG coating, respectively.
Point 8: Fig. 5. The Tafel plots should be represented on the figure and the corresponding values should be listed.
Response8: Thank you for your suggestion. The polarization curve has been given in the manuscript, and the corresponding values are listed.
Point 9: The corrosion potential values in Table 3 seem to be obtained from the polarization curves of Fig. 6. However, did they coincide with the open circuit values? This should be linked to the EIS measurements. Were they obtained at these potential values?
Response 9: Thank you for your suggestion.
- The data of Table 3 wer obtained from the polarization curves of Fig. 6.
- It is basically the same as the open circuit value, but slightly different, which is caused by the different corrosion resistance of the film surface and the interface.
(3) In the experiment or get the open circuit value of each group, add it to Table 3, as follows
Table 3. Corrosion current densities and corrosion potentials for different coatings in SBF at 37 ± 1 °C
|
Sample |
UMAO |
UMAO/PLGA |
UMAO/PLGA/NG |
|
|
Open Ecorr（V） |
-1.827 |
-1.546 |
-1.565 |
|
|
Ecorr（V） |
-1.829 |
-1.513 |
-1.573 |
|
|
Icorr (A/cm2) |
2.53×10-6 |
1.74×10-7 |
3.6×10-8 |
|
Point 10: How was the error of Ecor in Table 2 determined? Repetitive experiments? And the error in Icor? The number of decimals in the error should not exceed those of the given values (i.e. 0.02 for 2.53).
Response 10: Thank you for your suggestion. This part reorganizes the data, this time only the results of one experiment are shown.
Table 3. Corrosion current densities and corrosion potentials for different coatings in SBF at 37 ± 1 °C
|
Sample |
UMAO |
UMAO/PLGA |
UMAO/PLGA/NG |
|
|
Open Ecorr（V） |
-1.827 |
-1.546 |
-1.565 |
|
|
Ecorr（V） |
-1.829 |
-1.513 |
-1.573 |
|
|
Icorr (A/cm2) |
2.53×10-6 |
1.74×10-7 |
3.6×10-8 |
|
Point 11: The EIS results are very dependent on the coating. This is nice. The experimental values have been fitted to the equivalent circuit in Fig. 6d. It is important to report evidences about the use of such an equivalent circuit (literature references missing).
Response 11: Thank you for your suggestion. We have added the references.
[43] Peng, S.h.; Li, M.Q.; Wang, J.Y. Corrosion behavior and biological activity of micro-arc oxidation coating with puerarin on pure magnesium surface. Results in Physics 2019, 12, 1481–1489. [CrossRef]
[20] Wang, J.Y.; Li, M.Q.; Zhang; D.Q. Corrosion resistance and cell compatibility in vitro of Chinese herbal extract coating on magnesium. Results in Physics 2019, 12, 1465–1474. [CrossRef]
Once again, thank you very much for your constructive comments and suggestions which would help us both in English and in depth to improve the quality of the paper.
Kind regards,
Liting Mu
E-mail: muliting@163.com
Corresponding author:
Zhen Ma
E-mail address: mz252930179@163.com
Muqin Li
E-mail address: jmsdxlimuqin@163.com
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The paper has been significatly revised according to Reviewer's comments and I feel that it is now suitable for publication.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
