Recent Advances in Polyoxometalates Targeting Proteins Associated with Alzheimer’s Disease: From Molecular Mechanisms to Therapeutic Applications

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript entitled “Recent advances in polyoxometalates targeting proteins associated with Alzheimer's disease: from molecular mechanisms to therapeutic applications” presents a well-structured and insightful systematic review. It effectively summarizes mechanisms of action, highlights therapeutic advantages, and offers valuable guidance for future POM design and clinical translation.

Abstract scope: The abstract states that the review 'systematically summarizes recent advances in POMs,' but does not specify the time frame covered (e.g., publications from 2014–2025). Clarifying this would help readers assess the review's scope and timeliness. 

Literature Gaps: The review offers a thorough synthesis of POM advances for AD treatment; however, several pertinent recent studies on relevant POM hybrids and their properties appear overlooked. Consider incorporating the following to enhance coverage of structural design and potential mechanisms:

• Sławińska, A.; Tyszka-Czochara, M.; Serda, P.; Oszajca, M.; Ruggiero-Mikołajczyk, M.; Pamin, K.; Napruszewska, B. D.; Prochownik, E.; Łasocha, W. New Organic-Inorganic Hybrid Compounds Based on Sodium Peroxidomolybdates (VI) and Derivatives of Pyridine Acids: Structure Determination and Catalytic Properties. Materials 2022, 15 (17), 5976.
• Tonkushina, M.; Belozerova, K.; Gagarin, I.; Adamova, L.; Terziyan, T.; Russkikh, O.; Ostroushko, A. Thermodynamics of the interaction between Keplerate-type polyoxometalate {Mo72Fe30} and vitamin B1. Thermochimica Acta 2022, 711, 179201.
• Rambaran, M. A.; Gorzsás, A.; Holmboe, M.; Ohlin, C. A. Polyoxoniobates as molecular building blocks in thin films. Dalton Transactions 2021, 50 (44), 16030-16038.
• Wang, M.; Hua, J.; Zheng, P.; Tian, Y.; Kang, S.; Chen, J.; Duan, Y.; Ma, X. A Nanoscale Cobalt Functionalized Strandberg-Type Phosphomolybdate with β-Sheet Conformation Modulation Ability in Anti-Amyloid Protein Misfolding. Inorganics 2023, 11 (11), 442.
• Ensure that all figures are clear.

Author Response

Thank you for your positive comments. We have revised our manuscript according to the suggestions.

 

Comment (C) 1: Abstract scope

Answer (A) 1: The time frame covered by this review has been clarified in the Abstract.

 

C2: Literature Gaps

A2: The relevant references suggested by the reviewer have been incorporated and discussed in the main text.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, the authors present a comprehensive and well-organised review of recent advances in the application of polyoxometalates (POMs) for targeting protein systems associated with Alzheimer’s disease (AD), integrating both structural chemistry and biomedical aspects. The authors effectively combine chemical design strategies, biological mechanisms, and therapeutic applications, addressing molecular-level interactions, inhibition of Aβ aggregation, phototherapeutic modalities, artificial protease activity, and interventions on other AD-related proteins (S100A9, AChE, and BChE). The inclusion of phototherapy (PDT/PTT) and artificial proteases is particularly noteworthy, as it extends the discussion beyond electrostatic models and highlights new design paradigms in functional materials.

The objective is clearly defined and appropriate for a review article, specifying the scope (POM–protein interactions), the targets (Aβ, AChE, BChE, S100A9), and the focus (mechanistic understanding and structure–activity relationships).

In general, the manuscript demonstrates a good literature coverage and technical depth; however, some issues need to be addressed to elevate it. The manuscript is descriptive and has limited critical analysis. Comparative evaluation of mechanistic pathways, relative efficacies, and toxicity of POM-based nanocomposites and artificial proteases is limited, and quantitative comparisons are rarely provided. Including a concise summary highlighting key outcomes and unresolved challenges, such as stability, toxicity, and BBB penetration, would significantly strengthen the review.

Here is some feedback to help improve the manuscript, under each section of the manuscript

Section 1

1. The statement in the abstract (line 18) describing POMs as ‘excellent biocompatible’ seems inconsistent with the introduction (line 87) and the summary of section 2 (line 412), which notes their high toxicity and safety concerns. Please clarify whether this description refers to modified POM derivatives or to the entire POM class.
2. The selection of the four proteins (Aβ, AChE, BChE, S100A9) is scientifically sound; however, the current explanation for narrowing from ten to four targets lacks sufficient clarity and explicit justification. Also, the authors should elaborate on the rationale for excluding the remaining six proteins, perhaps by adding one or two sentences indicating why they are not discussed.

Section 2

1. Merge repetitive subsections 2.1 and 2.1.1 under a single coherent heading (Inhibition of Aβ aggregation by POMs).
2. The inclusion of Table 1 is a notable strength of the manuscript. It already consolidates the therapeutic landscape by cataloguing 28 POM systems. This extensive compilation provides readers with a valuable overview of compound diversity, molecular mechanisms, and literature coverage. To further enhance the analytical value of Table 1, I recommend the following refinements:

• Include quantitative indicators (e.g., Aβ inhibition rate, IC₅₀, or relative ROS-generation capacity), where data exist.
• Where feasible, highlight multifunctional systems that act on multiple targets (e.g., Aβ + cholinesterases or Aβ + S100A9) to emphasize cross-pathway intervention potential. It strengthens the claim that POMs represent a multi-mechanistic therapeutic platform, one of the manuscript’s key conclusions. To highlight this multifunctionality, the authors could add a symbol or footnote (e.g., † or *) next to POMs that show dual or multi-target effects and explain it in the caption.

The suggested refinements would help Table 1 move beyond a descriptive toward a more comparative and analytical format, thereby capturing the structural diversity and biological depth of current POM-based therapeutic studies.

3. The manuscript mentions the toxicity and selectivity of POMs at several points (lines 85–97, 195–203, 226–240, 267–268, and 410–413); however, these sections remain descriptive. To enhance scientific depth, it is suggested that the authors:

• Clarify the structural factors influencing POM toxicity, such as surface charge density, oxidation state, and ligand substitution.
• Highlight any structure–toxicity or structure–selectivity correlations (e.g., differences between pure, hybrid, and chiral POMs).
• Summarise these insights in one short analytical paragraph to bridge chemistry and biomedical implications.

Section 3

It is well-structured but descriptive and needs a deeper mechanistic and practical context. The discussion of PDT and PTT lacks quantitative comparisons (e.g., ROS yield, wavelength dependence, photothermal conversion efficiency).

Section 5

The inclusion of S100A9 and CHE is valuable; however, it is brief compared to Aβ. Just make sure that a more balanced analysis is not possible.

Section 6

1. The two sentences from lines 672–677 seem redundant. You can merge them into a single, sharper sentence, or if you prefer to retain both for rhetorical emphasis, you could differentiate them.
2. In the future research direction section (line 695), the authors may consider revising the phrase ‘…reinforce efforts toward clinical translation…’ to include preclinical translation. Since POM-based systems are largely in early stages of development, highlighting preclinical pharmacological validation and toxicity assessment would provide a more realistic and stepwise roadmap toward eventual clinical application.
3. The authors mentioned molecular docking studies (lines 680–682), but future directions could also highlight emerging AI-assisted computational design approaches that extend beyond conventional docking. Such methods could accelerate the rational optimisation of POM structures and improve target selectivity.

Figure issues: If some figures are reproduced from sources, they should be properly cited. Additionally, some figures have legibility problems: e.g.,  Figures 10a and 12 contain texts that are difficult to read.  

Author Response

Thank you for your positive comments. We have revised our manuscript according to the suggestions.

 

Comment (C) : Overall critical analysis and comparative evaluation. The manuscript demonstrates good literature coverage and technical depth; however, it is descriptive and has limited critical analysis. Comparative evaluation of mechanistic pathways, relative efficacies, and toxicity of POM-based nanocomposites and artificial proteases is limited, and quantitative comparisons are rarely provided. Including a concise summary highlighting key outcomes and unresolved challenges, such as stability, toxicity, and BBB penetration, would significantly strengthen the review.

Answer (A) : POM-based nanocomposites: The manuscript has been revised to strengthen critical analysis and comparative discussion. Representative POM-based nanocomposites are now compared in terms of mechanistic pathways, relative efficacy, toxicity, and BBB-related performance, with quantitative data incorporated where available. A concise summary and outlook section has also been added to highlight key outcomes and unresolved challenges, including stability, long-term toxicity, and limitations in BBB penetration and evaluation.

Artificial proteases: We have added comparative analyses of mechanistic pathways, efficacy, and ROS-scavenging activity for AuNPs@POMD-8pep and CeONP@POMs, including quantitative data and a summary of key outcomes and remaining challenges such as stability, toxicity, and BBB penetration.

 

Section 1:

 

C1: The statement in the abstract (line 18) describing POMs as ‘excellent biocompatible’ seems inconsistent with the introduction (line 87) and the summary of section 2 (line 412), which notes their high toxicity and safety concerns. Please clarify whether this description refers to modified POM derivatives or to the entire POM class.

A1: The description of POMs as “excellent biocompatible” in the abstract has been revised. The statement in line 87 remains, as it specifically refers to the high toxicity of purely inorganic POMs. Line 412 is revised. Although modified POMs may exhibit reduced toxicity compared to pure POMs, challenges in optimizing toxicity and biocompatibility persist.

 

C2: The selection of the four proteins (Aβ, AChE, BChE, S100A9) is scientifically sound; however, the current explanation for narrowing from ten to four targets lacks sufficient clarity and explicit justification. Also, the authors should elaborate on the rationale for excluding the remaining six proteins, perhaps by adding one or two sentences indicating why they are not discussed.

A2: The rationale for excluding the remaining six proteins has been added in the main text.

 

Section 2:

 

C3: Merge repetitive subsections 2.1 and 2.1.1 under a single coherent heading (Inhibition of Aβ aggregation by POMs).

A3: The subsections 2.1 and 2.1.1 have been merged under the heading “2.1. Inhibition of Aβ aggregation by pure POMs” to provide a single coherent section focused on purely inorganic POMs.

 

C4: Table 1 provides a valuable overview of 28 POM systems. Its analytical value could be further enhanced by including quantitative indicators (e.g., Aβ inhibition rate, IC₅₀, ROS-generation capacity) where available, and by highlighting multifunctional systems, particularly those acting on multiple targets, using a symbol or footnote.

A4: We have addressed this suggestion by adding a new column to Table 1 titled “Multi-target Effects”. POMs exhibiting dual or multi-target activity are marked with an asterisk (*). This is explained in the table caption.

 

C5: The manuscript discusses POM toxicity and selectivity at multiple sections (lines 85–97, 195–203, 226–240, 267–268, and 410–413), but the treatment is largely descriptive. To strengthen the scientific depth, the authors should clarify the structural factors affecting POM toxicity (e.g., surface charge density, oxidation state, ligand substitution), highlight any correlations between structure and toxicity/selectivity (such as differences among pure, hybrid, and chiral POMs), and summarize these insights in a concise analytical paragraph that links chemical structure with biomedical implications.

A5: A short analytical paragraph summarizing the structure-dependent toxicity and selectivity of POMs has been added to the revised manuscript.

 

Section 3:

 

C6: It is well-structured but descriptive and needs a deeper mechanistic and practical context. The discussion of PDT and PTT lacks quantitative comparisons (e.g., ROS yield, wavelength dependence, photothermal conversion efficiency).

A6: We have revised the section to provide more mechanistic and practical context. Quantitative details, including ROS generation efficiency, wavelength dependence, and photothermal conversion performance of PDT- and PTT-based POM systems, have been added where data are available. Comparative discussion between PDT and PTT has also been included to clarify their complementary roles in AD therapy.

 

Section 5:

 

C7: The inclusion of S100A9 and CHE is valuable; however, it is brief compared to Aβ. Just make sure that a more balanced analysis is not possible.

A7: We acknowledge the reviewer’s comment. Current studies on POMs primarily focus on Aβ, with only very few reports addressing S100A9 or CHE. Therefore, the discussion of S100A9 and CHE in the manuscript is necessarily concise, reflecting the limited available evidence, and a more balanced analysis is not feasible at this stage.

 

Section 6:

 

C8: The two sentences from lines 672–677 seem redundant. You can merge them into a single, sharper sentence, or if you prefer to retain both for rhetorical emphasis, you could differentiate them.

A8: We have deleted the second, repetitive sentence to remove redundancy while retaining the original meaning.

 

C9: In the future research direction section (line 695), the authors may consider revising the phrase ‘…reinforce efforts toward clinical translation…’ to include preclinical translation. Since POM-based systems are largely in early stages of development, highlighting preclinical pharmacological validation and toxicity assessment would provide a more realistic and stepwise roadmap toward eventual clinical application.

A9: We have revised the text to emphasize preclinical translation, including pharmacological validation and toxicity assessment, in line with the early-stage development of POM-based systems.

 

C10: The two sentences from lines 672–677 seem redundant. You can merge them into a single, sharper sentence, or if you prefer to retain both for rhetorical emphasis, you could differentiate them.

A10: We have deleted the second, repetitive sentence to remove redundancy while retaining the original meaning.

 

C11: The authors mentioned molecular docking studies (lines 680–682), but future directions could also highlight emerging AI-assisted computational design approaches that extend beyond conventional docking. Such methods could accelerate the rational optimisation of POM structures and improve target selectivity.

A11: The manuscript has been revised to incorporate AI-assisted computational design approaches as suggested, highlighting their potential to complement conventional molecular docking for more efficient POM optimization and improved target selectivity.

 

C12: Figure issues: If some figures are reproduced from sources, they should be properly cited. Additionally, some figures have legibility problems: e.g., Figures 10a and 12 contain texts that are difficult to read.  

A12: All reproduced figures have been properly cited with references in the captions. Figures 10a and 12 have been updated to improve text legibility.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This review systematically examines the ability of polyoxometalates (POMs) to target key pathogenic proteins in Alzheimer's disease (AD). It analyzes the underlying mechanisms involved and presents evidence supporting the broad potential of POMs for AD treatment. The excellent review effectively covers a wide range of topics clearly and convincingly. It includes examples of successful work conducted by the authors, who are well-positioned to provide valuable insights. I have no major concerns and fully support the publication of the manuscript. I have included a few suggestions that the authors might consider, but these minor comments could be easily disregarded without affecting the overall quality of the review.

 

 Specific points:

 - POMs possess outstanding physicochemical properties that allow them to specifically bind to proteins via various intermolecular forces, enabling interactions with a large number of proteins. Their elemental composition, charge distribution, and spatial configuration also suggest they could recognize and interact with numerous proteins, not just the key targets in AD. This may raise questions about the implications of such interactions concerning biological activity and potential toxicity. Furthermore, their promising reactivity with other biomolecules, such as nucleic acids, nucleotides, and sugars, merits further exploration.

 - In Figure 15, the molecular dynamics simulation suggests an interaction between S100A9 and POMs. Is there any experimental evidence supporting this 3D assembly or other POM-protein assemblies that could further validate the potential of POMs to interact with biomolecules?

- Most documented POM-protein interactions involve soluble proteins. Are there any examples of interactions with membrane proteins, despite the hydrophilicity of POMs?

 

 

Author Response

Thank you for your positive comments. We have revised our manuscript according to the suggestions.

 

Comment (C) 1: POMs possess outstanding physicochemical properties that allow them to specifically bind to proteins via various intermolecular forces, enabling interactions with a large number of proteins. Their elemental composition, charge distribution, and spatial configuration also suggest they could recognize and interact with numerous proteins, not just the key targets in AD. This may raise questions about the implications of such interactions concerning biological activity and potential toxicity. Furthermore, their promising reactivity with other biomolecules, such as nucleic acids, nucleotides, and sugars, merits further exploration.

Answer (A) 1: Purely inorganic POMs possess high surface charge density and uniform surface oxygen distribution, which can lead to non-specific interactions with various biomolecules, such as nucleic acids, nucleotides, and sugars, potentially resulting in cytotoxicity and low selectivity. To address these limitations, functionalization strategies—including organic ligand substitution, transition metal doping, chiral modifications, and the design of POM-based nanocomposites—have been developed to enhance target specificity toward AD-related proteins, improve biocompatibility, and reduce non-specific interactions. In this review, we focus on POM interactions with key AD-related proteins (Aβ, AChE, BChE, and S100A9) and their therapeutic implications. In this review, we focus on the four targets highlighted above, which are widely recognized as the most critical in the current research landscape. Although other potential targets are briefly referenced for contextual completeness, they are beyond the scope of this discussion. To ensure clarity and maintain a focused analysis, we provide succinct explanations for their exclusion from detailed consideration.

 

 

C2: In Figure 15, the molecular dynamics simulation suggests an interaction between S100A9 and POMs. Is there any experimental evidence supporting this 3D assembly or other POM-protein assemblies that could further validate the potential of POMs to interact with biomolecules?

A2: While no high-resolution experimental 3D structure of the S100A9–POM complex is available, multiple biophysical experiments provide evidence for other POM–protein assemblies. Fluorescence titration, acrylamide quenching, and circular dichroism measurements all demonstrate specific and measurable interactions between POMs and S100A9, consistent with the binding interfaces and dynamics predicted by molecular dynamics simulations. These results support the potential of POMs to interact with biomolecules, even in the absence of direct 3D structural data.

 

C3: Most documented POM-protein interactions involve soluble proteins. Are there any examples of interactions with membrane proteins, despite the hydrophilicity of POMs?

A3: Most documented POM–protein interactions are indeed with soluble proteins. However, there are reports showing that POMs can also interact with membrane systems or membrane-associated environments despite their intrinsic hydrophilicity. For instance, certain POMs have been found to interact directly with lipid bilayers and artificial membranes, affecting liposome ζ-potential and exhibiting membrane adsorption that depends on POM composition and lipid charge [1]. This demonstrates that POMs can associate with lipid interfaces beyond purely soluble proteins. In single-molecule studies, POMs were observed to induce pore formation and assemble with lipids in model membranes, indicating that they can organize with membrane lipids and perturb membrane structure [2]. Additionally, some POM species have been shown to adsorb onto membrane surfaces and form stable POM–lipid conjugates, leading to membrane disruption and revealing interactions beyond soluble protein binding [3]. These examples suggest that, although high-resolution structural data for specific POM–membrane protein complexes are limited, POMs are capable of interacting with membranes or membrane mimetics, implying potential interactions with membrane proteins or membrane-proximal biomolecules despite their hydrophilic nature.

[1] Bijelic, A., Aureliano, M., Rompel, A. Polyoxometalates as Potential Next-Generation Metallodrugs in the Combat Against Cancer. Angew. Chem. Int. Ed. 2019, 58, 2980-2999.

[2] Pashkovskaya, A. A., Gumerova, N. I., Rompel, A., Pohl, E. E. Molecular interactions at the interface: polyoxometalates of the Anderson-Evans type and lipid membranes. Front. Chem. Biol. 2024, 3, 1454558.

[3] Sakamoto, A., Unoura, K., Nabika, H. Molecular Scale Insights into Activity of Polyoxometalate as Membrane-Targeting Nanomedicine from Single-Molecule Observations. J. Phys. Chem. C 2018, 122, 1404–1411.

Author Response File: Author Response.docx