Multifunctional Y₂O₃-Modified Borotellurite Bioactive Glasses for Bone Tissue Engineering Applications

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors

I am pleased to reviews your manuscript that contains significantly experiment. I have some suggestions that can be improved this manuscript.

• If possible please include the final chemical composition of the glasses. It will be clear to understand the properties depend on the composition.
• Figure 1 please identified the XRD phase composition in the figure.
• Please check the result of glass TBY7 during 250-350 nm in figure 3.
• Please explain more Why coated silver only TB and TBY3 glass.                        Thank you very much and Best regards.

Author Response

General Comments: I am pleased to reviews your manuscript that contains significantly experiment. I have some suggestions that can be improved this manuscript.

Response: We sincerely thank the reviewer for the positive evaluation of our manuscript and for recognizing the significance of the experimental work. We also appreciate the constructive suggestions provided, which have helped us to further improve the quality and clarity of the manuscript. All comments have been carefully considered, and the manuscript has been revised accordingly to address each point in detail.

Comments 1: If possible please include the final chemical composition of the glasses. It will be clear to understand the properties depend on the composition.

Response 1 : We sincerely thank the reviewer for this important and constructive suggestion. We fully agree that post-processing compositional verification is valuable for multicomponent glass systems, particularly after high-temperature melting, where volatilization, matrix effects, or melt–crucible interactions may influence the final composition.

We initially planned to perform bulk compositional verification of the produced glasses by ICP-MS/ICP-based analysis after complete digestion. However, due to an unexpected technical malfunction of the ICP-MS system and the limited time available for manuscript revision, this analysis could not be completed within the revision period. As an alternative, post-melting XRF analysis was performed to obtain compositional screening data. However, the XRF results did not show sufficient consistency with the nominal batch compositions, mainly because the present glass system contains light oxides, especially B₂O₃, which cannot be reliably quantified by conventional XRF. In addition, the apparent non-detection or inconsistent detection of some light/alkali oxides may be related to matrix effects, detection limits, and calibration sensitivity in this Te–B–P–Ca–Na–Y multicomponent glass system. Therefore, we considered that presenting the XRF data in the main manuscript as absolute final stoichiometric compositions could be misleading and might lead to overinterpretation.

To address the reviewer’s concern transparently, the XRF results have been provided as Supplementary Information (please check supplementary files) and are clearly described as semi-quantitative post-melting compositional screening data rather than definitive final glass compositions. In the revised manuscript, we have also clarified that the compositions given in Table 2 represent the nominal molar batch compositions used as the controlled design variable of the study. The composition–property relationships were therefore interpreted based on these nominal compositions together with complementary structural, thermal, mechanical, ion-release, bioactivity, cytocompatibility, and antibacterial analyses.

We have also added a limitation statement (on page 30) indicating that future work should include fully validated bulk compositional verification by ICP-OES/ICP-MS after complete glass digestion.

Comments 2: Figure 1 please identified the XRD phase composition in the figure.

Response 2: We sincerely thank the reviewer for this helpful comment. We agree that the crystalline phase assignment should be clearly indicated in Figure 1 to improve the readability and interpretation of the XRD results. Accordingly, Figure 1 has been revised by marking the detected diffraction peaks and identifying the corresponding crystalline phase.

In the revised Figure 1, the diffraction peaks observed in the Y₂O₃-containing glasses are now labeled as xenotime-type YPO₄, consistent with the phase identification performed using the ICDD PDF-4+ database. 

 Comments 3: Please check the result of glass TBY7 during 250-350 nm in figure 3.

Response 3: We appreciate your observation. The UV–Vis spectrum of TBY7 differs from the other samples. Accordingly, we revised the manuscript to state: “All compositions except TBY7 exhibited broad absorption behavior without a sharp absorption edge, which is characteristic of amorphous materials and is consistent with the XRD results confirming the predominantly glassy nature of the system [47].”

Comments 4: Please explain more Why coated silver only TB and TBY3 glass. 

Response 4: We thank the reviewer for this helpful comment. TB was selected as the unmodified reference composition to evaluate the direct effect of silver coating on the base borotellurite glass. TBY3 was selected as the representative Y₂O₃-modified glass because it showed the most balanced overall performance, combining good cytocompatibility, improved mechanical behavior, controlled ion release, and favorable antibacterial response. Although some compositions showed higher values in individual parameters, TBY3 provided the best compromise among the investigated properties. Therefore, silver coating was applied to TB and TBY3 to compare the effect of Ag-based surface functionalization on both the base glass and the optimized Y₂O₃-containing composition. Furthermore, the following explanation text was added to “2.4. Silver Coating” on page 8:

Added text:

“Silver surface modification was applied to the undoped TB glass and the TBY3 composition, selected as the optimal Y₂O₃-doped sample based on its balanced mechanical performance, cytocompatibility, controlled ion-release behavior, and preliminary antibacterial response. TB was chosen as the unmodified reference composition to assess the direct effect of Ag-based surface functionalization on the base borotellurite glass. TBY3 was selected as the representative Y₂O₃-modified composition because it provided the most balanced combination of cytocompatibility, mechanical performance, controlled ion release, and antibacterial behavior among the doped glasses. Although TBY1 showed the highest long-term viability and TBY7 exhibited the highest hardness and cell adhesion, TBY3 demonstrated a more favorable overall compromise without the pronounced reduction in compressive strength observed at higher Y₂O₃ contents. Therefore, coating TB and TBY3 enabled a direct comparison between the base glass and an optimized Y₂O₃-containing composition while keeping the experimental design focused.”

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

The manuscript entitled “Multifunctional Y₂O₃-Modified Borotellurite Bioactive Glasses for Bone Tissue Engineering Applications” presents a systematic study on rare-earth (Y₂O₃) doped borotellurite bioactive glasses, focusing on their structural, thermal, mechanical, biological, and antibacterial properties. While the topic is relevant to the scope of Journal of Functional Biomaterials, and the manuscript demonstrates a reasonably comprehensive experimental effort, there are several critical concerns regarding scientific depth, validation, and translational significance.

Here are my main concerns:

1. The incorporation of rare-earth oxides into bioactive glass systems is not fundamentally novel, and similar strategies using Ce, La, Sr, and Zn have been extensively reported. The claimed “multifunctionality” (mechanical enhancement + antibacterial + cytocompatibility) is expected behavior for such doped systems and is not sufficiently distinguished from existing literature. The following recent literature maybe helpful to you in the introduction section:

https://doi.org/10.1016/j.jallcom.2026.187463

https://doi.org/10.1016/j.colsurfa.2025.139019

2. Insufficient Biological Validation is the significant weakness of this manuscript. I would like to recommend that ALP activity, mineralization, gene expression
3. Lack of Surface and Interface Characterization, I would like to suggest that included the XPS characterization.
4. Recommends the compositional verification (e.g., ICP-OES/XRF) despite high-temperature processing.

Author Response

General comments: The manuscript entitled “Multifunctional Y₂O₃-Modified Borotellurite Bioactive Glasses for Bone Tissue Engineering Applications” presents a systematic study on rare-earth (Y₂O₃) doped borotellurite bioactive glasses, focusing on their structural, thermal, mechanical, biological, and antibacterial properties. While the topic is relevant to the scope of Journal of Functional Biomaterials, and the manuscript demonstrates a reasonably comprehensive experimental effort, there are several critical concerns regarding scientific depth, validation, and translational significance. Here are my main concerns:

Response: We sincerely thank the reviewer for the careful evaluation of our manuscript and for acknowledging the relevance of the topic and the comprehensive experimental effort. We have carefully considered all critical concerns regarding scientific depth, validation, and translational significance. Accordingly, the manuscript has been revised to strengthen the mechanistic discussion, clarify the experimental rationale, better define the limitations, and present the translational relevance in a more balanced manner.

Comments 1: The incorporation of rare-earth oxides into bioactive glass systems is not fundamentally novel, and similar strategies using Ce, La, Sr, and Zn have been extensively reported. The claimed “multifunctionality” (mechanical enhancement + antibacterial + cytocompatibility) is expected behavior for such doped systems and is not sufficiently distinguished from existing literature. The following recent literature may be helpful to you in the introduction section:

https://doi.org/10.1016/j.jallcom.2026.187463

https://doi.org/10.1016/j.colsurfa.2025.139019

Response 1: We thank the reviewer for the useful suggestion. In the revised manuscript, we now more clearly acknowledge previous studies on ion-modified bioactive glasses and glass–ceramic systems, including systems containing Sr, Zn, Ce, La, and Ag. Following the reviewer’s suggestion, the two recommended recent studies have also been cited in the Introduction and used to better position the present work within the current literature.

We have clarified that the novelty of this study is not based solely on Y₂O₃ addition, but rather on the systematic investigation of Y₂O₃ in a TeO₂-rich borotellurite bioactive glass matrix, particularly with respect to long-term Te release regulation, cytocompatibility, mechanical response, bioactive surface reactions, and antibacterial behavior. The novelty statement has therefore been revised to present the contribution of the study in a more balanced and literature-supported manner.

Comments 2: Insufficient Biological Validation is the significant weakness of this manuscript. I would like to recommend that ALP activity, mineralization, gen expression.

Response 2: We sincerely thank the reviewer for this important and constructive comment. We agree that additional osteogenic validation, including ALP activity, mineralization assays, and osteogenic gene-expression analysis, would provide stronger biological evidence regarding the bone-regenerative potential of the developed glasses.

In the present study, the biological evaluation was designed as an initial in vitro assessment, including MC3T3-E1 cytocompatibility, osteoblast adhesion/spreading morphology, SBF-related bioactivity, ion-release behavior, and antibacterial performance. We acknowledge that these analyses do not fully confirm osteogenic differentiation.

Accordingly, we have revised the manuscript and added a dedicated subsection entitled “3.5. Limitations and Future Perspectives” on page 30. In this section, we explicitly state that future studies should include ALP activity, Alizarin Red S-based mineralization quantification, and osteogenic gene-expression analysis of markers such as RUNX2, ALP, COL1A1, OCN, and OPN.

Comments 3: Lack of Surface and Interface Characterization, I would like to suggest that included the XPS characterization.

Response 3: We sincerely thank the reviewer for this valuable suggestion. We agree that XPS analysis would provide important additional information regarding the surface chemical states, elemental composition, and interfacial characteristics of the Y₂O₃-modified and Ag-coated glasses.

In the present study, the surface-related evaluation was mainly based on SEM/FESEM observations, SBF-induced surface reaction analysis by XRD/FTIR, cell-adhesion morphology, and antibacterial adhesion assays. These analyses allowed us to assess surface morphology, apatite-related surface reactions, and biological/bacterial interactions. However, we acknowledge that XPS would further strengthen the surface and interface characterization, particularly by confirming the chemical states of Ag, Y, Te, P, Ca, and O on the glass surface and after coating.

Due to current experimental and time limitations during the revision period, XPS analysis could not be added to the present version. To address the reviewer’s concern, we have revised the manuscript to explicitly state this limitation in Section 3.5. Limitations and Future Perspectives on page 30. We now indicate that future studies should include XPS analysis to clarify surface chemical states, Ag-related surface chemistry, and coating–glass interfacial interactions more comprehensively. 

Comments 4: Recommends the compositional verification (e.g., ICP-OES/XRF) despite high-temperature processing.

Response 4: We sincerely thank the reviewer for this important and constructive suggestion. We fully agree that post-processing compositional verification is valuable for multicomponent glass systems, particularly after high-temperature melting, where volatilization, matrix effects, or melt–crucible interactions may influence the final composition.

We initially planned to perform bulk compositional verification of the produced glasses by ICP-MS/ICP-based analysis after complete digestion. However, due to an unexpected technical malfunction of the ICP-MS system and the limited time available for manuscript revision, this analysis could not be completed within the revision period. As an alternative, post-melting XRF analysis was performed to obtain compositional screening data. However, the XRF results did not show sufficient consistency with the nominal batch compositions, mainly because the present glass system contains light oxides, especially B₂O₃, which cannot be reliably quantified by conventional XRF. In addition, the apparent non-detection or inconsistent detection of some light/alkali oxides may be related to matrix effects, detection limits, and calibration sensitivity in this Te–B–P–Ca–Na–Y multicomponent glass system. Therefore, we considered that presenting the XRF data in the main manuscript as absolute final stoichiometric compositions could be misleading and might lead to overinterpretation.

To address the reviewer’s concern transparently, the XRF results have been provided as Supplementary Information (please check supplementary files) and are clearly described as semi-quantitative post-melting compositional screening data rather than definitive final glass compositions. In the revised manuscript, we have also clarified that the compositions given in Table 2 represent the nominal molar batch compositions used as the controlled design variable of the study. The composition–property relationships were therefore interpreted based on these nominal compositions together with complementary structural, thermal, mechanical, ion-release, bioactivity, cytocompatibility, and antibacterial analyses.

We have also added a limitation statement (on page 30) indicating that future work should include fully validated bulk compositional verification by ICP-OES/ICP-MS after complete glass digestion.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear author

 

This is good paper but need some changes before to be accepted.

This paper could be improved it. Please see my suggestions from below:

 

 

mol%=mol.%

 

!!!!!!!!!!!!!!!!

Please provide detailed information of all the instrument, reagent (manufacturer name/location), and system, software (version no.) emerged in the paper. Part of them have been highlighted. Please check them throughout the paper

 

Please see all article

Merck),

TeO2 (99.9%, Nanografi Inc.

 

Please provide a composition of SBF and reference. There are many composition

 

Figure 7. scale is not visible at printing

 

1. b) please indicate what you see there by arrows

 

 

Figure 12. sample legend is not necessary

 

 

Figure 13. scale is not visible at printing

 

 

Figure 14 Y scale should be set at 4 to be more visible

 

Conclusion could be shorter

Author Response

General comments: This is good paper but need some changes before to be accepted. This paper could be improved it. Please see my suggestions from below:

Response: We sincerely thank the reviewer for the positive evaluation of our manuscript and for considering it a good paper. We also appreciate the constructive suggestions provided to improve the manuscript before acceptance. All comments have been carefully addressed, and the manuscript has been revised accordingly to enhance its clarity, scientific quality, and overall presentation.

Comments 1: mol%=mol.%

Response 1: We thank the reviewer for this correction. The notation has been revised throughout the manuscript by replacing “mol%” with “mol.%” to ensure consistency with standard scientific formatting.

Comments 2: Please provide detailed information of all the instrument, reagent (manufacturer name/location), and system, software (version no.) emerged in the paper. Part of them have been highlighted. Please check them throughout the paper. Please see all article (Merck), TeO₂ (99.9%, Nanografi Inc.)

Response 2: We sincerely thank the reviewer for this careful and helpful comment. Accordingly, we have carefully checked the entire manuscript and revised the Materials and Methods section to include the manufacturer name, model, location, and, where applicable, software/database/version information for the reagents, instruments, and analytical systems used in the study.

Specifically, the raw materials listed in Section 2.1 have been revised to include supplier details, and the characterization methods have been updated with instrument model and manufacturer/location information for XRD, FTIR, UV–Vis spectroscopy, DTA, density measurement, microhardness testing, compression testing, ICP-MS, SEM/FESEM. All reagent, instrument, software, and database details, including manufacturer names, locations, and version/release information where applicable, were checked and standardized throughout the revised manuscript to improve reproducibility.

Comments 3: Please provide a composition of SBF and reference. There are many compositions.

Response 3: We sincerely thank the reviewer for this valuable comment. We agree that the composition of simulated body fluid (SBF) should be clearly provided because different SBF formulations have been reported in the literature. In the revised manuscript, we have clarified that SBF was prepared according to the protocol described by Kokubo and Takadama and added its ionic composition to the Materials and Methods section (2.5. Ion Release Quantification by ICP-MS).

Added text:

"The ionic composition of the SBF used in this study was as follows: Na⁺, 142.0 mM; K⁺, 5.0 mM; Mg²⁺, 1.5 mM; Ca²⁺, 2.5 mM; Cl⁻, 103.0 mM; HCO₃⁻, 27.0 mM; HPO₄²⁻, 1.0 mM; and SO₄²⁻, 0.5 mM. This composition was selected to approximate the inorganic ionic concentrations of human blood plasma and to assess the in vitro bioactive response of the prepared glasses under physiological-like conditions."

Comments 4: Figure 7. scale is not visible at printing (please indicate what you see there by arrows).

Response 4: We thank the reviewer for this helpful suggestion. Figure 7 has been revised by enlarging the annotations and adding clear arrows to indicate the coating layer, coating/substrate interface, glass substrate, coating thickness, granular coating morphology, agglomerated particles, and porous surface features.

Comments 5: Figure 12. sample legend is not necessary.

Response 5: We thank the reviewer for this helpful comment. The unnecessary sample legend in Figure 12 has been removed as suggested. 

Comments 6: Figure 13. scale is not visible at printing.

Response 6: We thank the reviewer for this helpful comment. Figure 13 has been revised to improve print readability by enlarging the scale bars and scale labels in all SEM panels. The revised figure now clearly shows the 10 µm scale in each image, allowing the cell morphology, lamellipodia, and filopodia features to be evaluated more easily in the printed version.

Comments 7: Figure 14 Y scale should be set at 4 to be more visible.

Response 7: We thank the reviewer for this helpful suggestion. Figure 14 has been revised by adjusting the Y-axis scale to 0.4, as recommended.

Comments 8: Conclusion could be shorter.

Response 8: We thank the reviewer for this helpful suggestion. We agree that the Conclusion section could be more concise. Accordingly, the Conclusion has been shortened by removing repetitive details and retaining only the key findings related to Y₂O₃ incorporation, cytocompatibility, bioactivity, antibacterial performance, and Ag-based surface functionalization.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors:

Thanks for addressing my comments adequately.