Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Overview of the Manuscript

This manuscript presents an extensive narrative review of the emerging evidence linking polymer micro- and nanoplastics (MPs/NPs) to red blood cell (RBC) structure and function. The authors provide a comprehensive synthesis of literature published between 2018 and 2025, tracing the conceptual shift of microplastics from environmental pollutants to biologically active contaminants detected in human blood. The review highlights significant uncertainties regarding exposure levels, in vivo toxicity, and long-term health consequences, and calls for a multidisciplinary approach to better assess the health risks associated with increasing microplastic exposure.

GENERAL COMMENT

The work is interesting, as the focus on RBCs as sensitive and clinically relevant targets represents a valuable contribution to the interdisciplinary interface between environmental toxicology, membrane biophysics, and hematology. The review is rich in mechanistic detail and provides a broad and in-depth analysis of the issues addressed. However, a more critical evaluation of several aspects would further strengthen the review.

SPECIFIC COMMENTS

- Throughout the text, some mechanistic concepts—such as oxidative stress, surface charge effects, and environmental aging—are repeated across multiple sections with similar wording. Condensing these concepts would improve the readability of the manuscript.

- The authors mainly adopt a descriptive approach; however, in sections addressing hemolysis thresholds, changes in deformability, and oxidative stress, the manuscript would benefit from a more critical evaluation of key parameters, including experimental concentrations, as well as inconsistencies or contradictions among the cited studies.

- Table 1. I suggest including the more representative references in the table.

Author Response

SPECIFIC COMMENTS

Comments: Throughout the text, some mechanistic concepts—such as oxidative stress, surface charge effects, and environmental aging—are repeated across multiple sections with similar wording. Condensing these concepts would improve the readability of the manuscript.

Response: We appreciate the reviewer's careful feedback. The manuscript has been revised to minimize repetitive language, particularly around oxidative stress, surface charge modulation, and environmental aging. Similar explanations have been merged or simplified where feasible. However, some repetition of key mechanistic ideas remains to preserve logical flow and coherence between sections. Because the review spans various topics and readers may focus on different parts, emphasizing core concepts was deemed helpful for clarity. We believe these updates strike a better balance between conciseness and readability.

 

Comments: The authors mainly adopt a descriptive approach; however, in sections addressing hemolysis thresholds, changes in deformability, and oxidative stress, the manuscript would benefit from a more critical evaluation of key parameters, including experimental concentrations, and from a discussion of inconsistencies or contradictions among the cited studies.

Response: This key point has been enhanced by expanding critical discussion in Sections 4.2 and 4.4. These sections now clearly detail the experimental concentration ranges, highlight differences across studies, and analyze how methodological variability influences reported thresholds. The revised content shifts from mere description to a more evaluative perspective on the existing evidence.

 

Comments: Table 1. I suggest including the more representative references in the table.

Response: We thank the reviewer for this suggestion. Table 1 has now been revised to incorporate key references, enhancing the support for the summarized findings and clarifying the link to the original literature.

Reviewer 2 Report

Comments and Suggestions for Authors

This review systematically summarizes the interactions between polymeric microplastics (MPs)/nanoplastics (NPs) and red blood cells (RBCs), focusing on how physicochemical factors (particle size, surface chemistry, environmental aging, protein corona formation) influence hemocompatibility. Key findings include that MPs/NPs can induce sublethal (reduced deformability, oxidative stress, altered ζ-potential, vesiculation, eryptosis) and lethal (hemolysis) effects on RBCs, with nanoscale (<200 nm) and positively charged particles posing the highest risk. The manuscript also discusses the clinical significance of these effects (e.g., impaired microcirculation, oxygen transport disruption) in vulnerable populations (neonates, transfusion recipients) and highlights current gaps (limited in vivo data, unclear long-term toxicity) and future research directions. However, I have the comments for improvement of this manuscript:

1. Strengthen in vivo and clinical evidence integration: Most data rely on in vitro studies; supplementing recent in vivo animal models or emerging clinical observations (e.g., MPs in human thrombi, transfusion-related adverse events) will enhance the clinical relevance and robustness of conclusions.
2. Expand comparative analysis of polymer types: The review touches on PS, PE, PET, etc., but lacks a systematic comparison of their differential toxicity to RBCs (e.g., hydrophobicity vs. hydrophilicity, biodegradable vs. non-biodegradable polymers). Adding a concise table or summary of polymer-specific effects will improve clarity.
3. Elaborate on protein corona mechanisms: The role of protein corona in modifying MPs/NPs-RBC interactions is mentioned but not fully detailed. Clarify how specific plasma proteins (e.g., albumin, fibrinogen) in the corona regulate particle adhesion, internalization, or toxicity to deepen mechanistic insights.
4. Include standardized methodologies and dose-response frameworks: Current studies use variable particle concentrations, exposure media, and assays. Discussing efforts to harmonize analytical methods (e.g., MP/NP quantification, hemocompatibility testing) or proposing reference dose ranges will help readers compare studies and guide future research.
5. Enhance coverage of indirect effects via other blood components: MPs/NPs interact with platelets, leukocytes, or endothelial cells—add a brief section on how these interactions indirectly affect RBC function (e.g., inflammation-induced oxidative stress, thrombosis-related microcirculation impairment) to improve comprehensiveness.
6. Dedicate focus to vulnerable populations with more data: The review mentions neonates and transfusion recipients but lacks specific studies on their unique susceptibility (e.g., immature RBC antioxidant systems, stored RBC "storage lesion" plus MP exposure). Supplementing targeted research summaries will strengthen clinical implications.

Author Response

Comments: 1. Strengthen in vivo and clinical evidence integration: Most data rely on in vitro studies; supplementing recent in vivo animal models or emerging clinical observations (e.g., MPs in human thrombi, transfusion-related adverse events) will enhance the clinical relevance and robustness of conclusions.

Response: To address this recommendation, a new dedicated subsection (Section 5.1) has been added. This section combines emerging in vivo animal data and recent clinical observations, including thrombus-associated MPs and transfusion-related considerations. The expanded discussion offers a clearer connection between in vitro findings and potential clinical implications.

 

Comments: 2. Expand comparative analysis of polymer types: The review touches on PS, PE, PET, etc., but lacks a systematic comparison of their differential toxicity to RBCs (e.g., hydrophobicity vs. hydrophilicity, biodegradable vs. non-biodegradable polymers). Adding a concise table or summary of polymer-specific effects will improve clarity.

Response: We have added a dedicated comparative analysis of polymer classes in Section 3.2.1, along with Table 1S. This section highlights polymer-specific traits such as hydrophobicity, aging behavior, and surface reactivity, along with their reported effects on RBCs, enhancing clarity and facilitating systematic comparison.

 

Comments 3: Elaborate on protein corona mechanisms: The role of protein corona in modifying MPs/NPs-RBC interactions is mentioned but not fully detailed. Clarify how specific plasma proteins (e.g., albumin, fibrinogen) in the corona regulate particle adhesion, internalization, or toxicity to deepen mechanistic insights.

Response: The revised manuscript now includes an expanded paragraph in Section 3.4 that offers a more detailed discussion on protein corona formation. It emphasizes how plasma proteins such as albumin and fibrinogen can influence particle adhesion, membrane interactions, and subsequent toxicity. This addition enhances the mechanistic foundation of the review.

 

Comments 4: Include standardized methodologies and dose-response frameworks: Current studies use variable particle concentrations, exposure media, and assays. Discussing efforts to harmonize analytical methods (e.g., MP/NP quantification, hemocompatibility testing) or proposing reference dose ranges will help readers compare studies and guide future research.

Response: A new Section 6 has been included to focus on methodological harmonization and exposure standardization. It features a structured dose-tier framework, along with Fig. 4 and Table 2, to assist in experimental design and cross-study comparisons. These updates aim to offer practical guidance for enhancing reproducibility and translational relevance in future research.

 

Comments 5: Enhance coverage of indirect effects via other blood components: MPs/NPs interact with platelets, leukocytes, or endothelial cells—add a brief section on how these interactions indirectly affect RBC function (e.g., inflammation-induced oxidative stress, thrombosis-related microcirculation impairment) to improve comprehensiveness.

Response: We concur that indirect interactions among platelets, leukocytes, and endothelial cells are biologically significant. The revised manuscript now features a brief paragraph discussing how inflammation, endothelial activation, and thrombotic processes may indirectly affect RBC function. However, we intentionally kept the main emphasis on direct MP/NP–RBC interactions to stay true to the review's core theme. A thorough exploration of responses within whole blood and the vascular system would require a separate, detailed analysis. We believe our current revision properly acknowledges these indirect pathways while preserving the overall focus.

 

Comments 6: Dedicate focus to vulnerable populations with more data: The review mentions neonates and transfusion recipients but lacks specific studies on their unique susceptibility (e.g., immature RBC antioxidant systems, stored RBC "storage lesion" plus MP exposure). Supplementing targeted research summaries will strengthen clinical implications.

Response: To bolster the clinical aspect, new subsections have been added to Section 5 focusing on neonatal susceptibility and transfusion-related issues. The added content covers immature antioxidant defenses, storage-lesion–induced membrane fragility, and the possible effects of combined MP exposure on stored RBC changes. This expansion improves the review's translational relevance.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

II REV

The work is largely improved and the weakness raised during the previous review process have been addressed. The sections that were questioned in the previous version have been carefully revised and are now supported by more appropriate and convincing arguments.

No more concerns

 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have taken the reviewers' comments seriously and revised the manuscript accordingly. In my opinion, the revised manuscript could be considered for publication