Flavonoids in Cancer Therapy: Nanocarrier Strategies to Overcome Bioavailability Limitations

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper explores the potential use of flavonoid nanoparticles in cancer therapy. Flavonoids have many proven properties that aid in the prevention and treatment of various cancers. However, unfavorable pharmacokinetic parameters, poor aqueous solubility, significant first-pass metabolism, rapid systemic clearance, and consequently low oral bioavailability limit their clinical application.
From experience over the past few decades, we know that nanoparticles can be very useful in such situations. Not only do they allow for the overcoming of many barriers in the body and protect the delivered substance, but when modified, they can deliver and release the drug at a precisely defined site (specifically targeting tissues or organs).
This paper examines the role of nanocarrier-based systems in overcoming the limitations associated with flavonoid bioavailability in anticancer therapy and highlights the prospects and challenges associated with implementing these particles for clinical use.

This topic is interesting and important in the context of the search for new therapeutic solutions in oncology. Due to the ever-increasing incidence of cancer, intensive research is being conducted worldwide on new, less harmful and more effective treatment methods. In many cases, our search is directed towards substances of natural origin. However, whether a substance is natural or synthetic, in addition to its primary action (in the case of cancer, cytotoxic, antiproliferative, antiangiogenic, proapoptotic), the most desirable feature is the ability to deliver the drug to a precisely defined, diseased site. This provides the greatest guarantee of achieving the desired effect.

As the authors point out, this publication is a traditional form of literature review, focused on a synthesis of topical research—a narrative review. The authors of the narrative review subjectively select the literature and present it descriptively. A literature search was conducted, focusing on the connections between flavonoids, anticancer therapy, and nanotechnology-based drug delivery systems.
As described in the Materials and Methods, PubMed/MEDLINE, ScienceDirect, and Scopus were used. The combinations of keywords and terms used are indicated. Inclusion criteria are presented. The selection process was based on the relevance of titles, abstracts, and full-text analysis.
The collected material is interesting and demonstrates the potential applications of flavonoids with nanoparticle delivery systems in oncology. The work submitted for review is an introduction to this topic. The literature in this area is quite limited.

There is always room for improvement in the form or content of the material presented, but the work submitted for review is presented in such a concise and engaging manner that it should encourage other researchers to familiarize themselves with the topic.

 

The conclusions summarize the issues raised in the publication: they highlight the difficulties in using flavonoids in therapy (despite their positive properties), point to nanocarrier-based drug delivery systems as the latest solutions in such cases, point out the specific advantages of such systems (such as the ability to overcome barriers, increased compound stability, targeted action, therapeutic efficacy with lower systemic toxicity), signal limitations (challenges related to large-scale production, batch reproducibility, regulatory approval and biological variability related to nano-biome interactions, lack of clinical trial results in this area) and highlight what may determine the future development and introduction of flavonoid nanoparticles into medical therapies.

The texts are tailored to the topic of the publication. However, there are several discrepancies in the way the cited publication is written – with the same number of authors, the bibliography sometimes lists one author et al., while other times lists all authors.

 Figures enhance the text, and tables organize important information.

What may be the risks associated with the use of the described molecules?

Author Response

Comment:
“This topic is interesting and important in the context of the search for new therapeutic solutions in oncology… The collected material is interesting and demonstrates the potential applications of flavonoids with nanoparticle delivery systems in oncology.”

Response:
We sincerely thank the reviewer for the careful evaluation of our manuscript and for the highly constructive and encouraging comments. We greatly appreciate the recognition of the scientific relevance, organization, and translational importance of this review, particularly regarding the role of flavonoid-based nanocarriers in overcoming pharmacokinetic limitations associated with anticancer therapy.

Comment:
“There are several discrepancies in the way the cited publication is written – with the same number of authors, the bibliography sometimes lists one author et al., while other times lists all authors.”

Response:
We thank the reviewer for identifying this important issue. The entire reference list was carefully revised and standardized according to the journal formatting guidelines. Inconsistencies related to author listing, use of “et al.”, citation formatting, and bibliographic presentation were corrected throughout the manuscript to ensure uniformity and compliance with the required style.

Comment:
“What may be the risks associated with the use of the described molecules?”

Response:
We appreciate this valuable observation. To address this point, additional discussion regarding the potential risks and limitations associated with flavonoid-based nanocarriers was incorporated into the revised manuscript, particularly in the “Future Perspectives” section. The revised text now discusses important concerns including physicochemical instability, batch-to-batch variability, potential toxicity associated with nanomaterials and residual formulation components, biological variability related to nano–bio interactions and protein corona formation, regulatory challenges, and the current scarcity of robust long-term clinical studies evaluating safety and efficacy in humans. These additions were included to provide a more balanced and translationally critical perspective regarding the clinical implementation of flavonoid-based nanomedicine.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

 

I have read and reviewed your manuscript entitled “Flavonoids in Cancer Therapy: Nanocarrier Strategies to Overcome Bioavailability Limitations”. Here are my recommendations:

 

1) In the Materials and Methods section, include the exact records you retrieved, how you included them, and how you excluded them from your review. If you applied the PRISMA guideline, add the respective flow diagram.

2) Structure the evidence from in vitro, in vivo, and clinical studies throughout the whole manuscript. Add tables if needed.

3) If applicable, provide a comparison between the pharmacokinetic outcomes of each type of nanocarrier included in the review.

4) If available, add data concerning the physicochemical properties of the nanocarriers (mean size, particle size distribution, zeta potential, etc.) and discuss them.

5) Describe the limitations of the included nanodelivery platforms.

6) Discuss the impact of protein corona formation on nanosystems’ integrity/efficacy more thoroughly.

7) Very few studies are included in each nanocarrier subsection. Expand the information.

8) Minor language issues (typos, inconsistent terminology) should be corrected throughout. Is the text in the boxes part of a table? Please, revise.

 

Kind regards,

The reviewer

Author Response

Comment 1:
“In the Materials and Methods section, include the exact records you retrieved, how you included them, and how you excluded them from your review. If you applied the PRISMA guideline, add the respective flow diagram.”

Response:
We sincerely thank the reviewer for this valuable methodological suggestion. The Materials and Methods section was substantially revised and expanded to provide a clearer description of the literature search strategy, consulted databases, keyword combinations, temporal coverage, inclusion and exclusion criteria, and study selection process. In addition, a literature screening and study selection workflow was incorporated (Figure 2) to improve methodological transparency and organization. Although the present work was designed as a narrative review rather than a strictly systematic review, the workflow was included to better illustrate the sequential screening and eligibility assessment process adopted by the authors.

Comment 2:
“Structure the evidence from in vitro, in vivo, and clinical studies throughout the whole manuscript. Add tables if needed.”

Response:
We appreciate this important recommendation. The manuscript was reorganized and expanded to better distinguish and contextualize evidence derived from in vitro, in vivo, and translational/preclinical investigations throughout the different nanocarrier sections. Additional comparative information and mechanistic discussion were incorporated to improve the organization and interpretation of the available evidence.

Comment 3:
“If applicable, provide a comparison between the pharmacokinetic outcomes of each type of nanocarrier included in the review.”

Response:
We thank the reviewer for this insightful suggestion. Additional discussion regarding pharmacokinetic improvements associated with different nanocarrier systems was incorporated throughout the manuscript, including enhancements in bioavailability, systemic exposure, circulation time, protection against degradation, and reduction of presystemic metabolism. Representative examples comparing free flavonoids and nanoencapsulated formulations were added to strengthen the translational discussion.

Comment 4:
“If available, add data concerning the physicochemical properties of the nanocarriers (mean size, particle size distribution, zeta potential, etc.) and discuss them.”

Response:
We appreciate the reviewer’s observation. Additional discussion concerning physicochemical parameters relevant to nanocarrier performance was included in the revised manuscript, particularly regarding mean particle size, polydispersity index (PDI), zeta potential, colloidal stability, and their influence on tumor accumulation, cellular uptake, and systemic behavior. The importance of these parameters for translational nanomedicine development was also emphasized.

Comment 5:
“Describe the limitations of the included nanodelivery platforms.”

Response:
We thank the reviewer for this important recommendation. The revised manuscript now includes a broader and more critical discussion regarding the limitations associated with flavonoid-based nanodelivery systems, including physicochemical instability, premature drug leakage, aggregation phenomena, large-scale manufacturing challenges, batch-to-batch reproducibility, variability of the EPR effect, potential toxicity related to residual formulation components, and regulatory barriers affecting clinical translation.

Comment 6:
“Discuss the impact of protein corona formation on nanosystems’ integrity/efficacy more thoroughly.”

Response:
We greatly appreciate this insightful comment. The discussion regarding protein corona formation was substantially expanded in the “Future Perspectives” section. The revised text now addresses how adsorption of proteins and biomolecules onto nanoparticle surfaces may alter colloidal stability, biodistribution, immune recognition, active targeting efficiency, and biological interactions. Additionally, the manuscript now discusses the influence of patient-specific physiological conditions on protein corona composition and its potential impact on therapeutic performance and translational reproducibility.

Comment 7:
“Very few studies are included in each nanocarrier subsection. Expand the information.”

Response:
We thank the reviewer for this valuable observation. All nanocarrier subsections were expanded with additional studies and mechanistic discussion involving liposomes, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), nanoemulsions, polymeric micelles, cyclodextrin complexes, and hybrid nanosystems. The revised version now provides broader coverage of recent advances and translational perspectives in flavonoid-based nanomedicine.

Comment 8:
“Minor language issues (typos, inconsistent terminology) should be corrected throughout. Is the text in the boxes part of a table? Please, revise.”

Response:
We appreciate the reviewer’s careful reading of the manuscript. The entire text was thoroughly revised to correct typographical issues, improve language consistency, standardize scientific terminology, and refine overall readability. Formatting inconsistencies involving text boxes, figure elements, and table presentation were also carefully revised and standardized throughout the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

The work is highly interesting within the field of medicinal chemistry, as natural compounds play a significant role in the development of new drugs, including anticancer agents.You noted that fla vonoids exhibit poor solubility and that clinical studies on them remain limited. It would be beneficial to expand the Introduction and, more broadly, the manuscript by including information on hybrid structures containing flavonoid fragments as potential anticancer agents. In particular, incorporating examples of hybrids with thiazole moieties could provide a clearer understanding of current design strategies for developing promising drug candidates.

Author Response

Comment:
“The work is highly interesting within the field of medicinal chemistry, as natural compounds play a significant role in the development of new drugs, including anticancer agents. You noted that flavonoids exhibit poor solubility and that clinical studies on them remain limited. It would be beneficial to expand the Introduction and, more broadly, the manuscript by including information on hybrid structures containing flavonoid fragments as potential anticancer agents. In particular, incorporating examples of hybrids with thiazole moieties could provide a clearer understanding of current design strategies for developing promising drug candidates.”

Response:
We sincerely thank the reviewer for this valuable and insightful suggestion. We fully agree that hybrid molecules containing flavonoid scaffolds represent an important and emerging strategy in medicinal chemistry for the development of novel anticancer agents with improved pharmacological and physicochemical properties.

In response to the reviewer’s recommendation, the Introduction section was expanded to include additional discussion regarding flavonoid-based hybrid molecules and multifunctional medicinal chemistry approaches designed to improve anticancer activity, molecular selectivity, and pharmacokinetic performance. The revised manuscript now highlights the growing interest in combining flavonoid scaffolds with other bioactive pharmacophores in order to enhance multitarget activity against cancer-related pathways, including PI3K/Akt/mTOR signaling.

Furthermore, specific mention of heterocyclic hybrid systems, including thiazole-containing flavonoid derivatives, was incorporated to better contextualize current rational drug design strategies aimed at overcoming limitations such as poor aqueous solubility, low bioavailability, and rapid metabolic degradation. These additions were included to strengthen the medicinal chemistry perspective of the review while maintaining the primary focus of the manuscript on nanocarrier-based delivery systems for flavonoid-mediated cancer therapy.

We greatly appreciate the reviewer’s recommendation, which significantly contributed to improving the scientific depth and translational relevance of the manuscript.

Reviewer 4 Report

Comments and Suggestions for Authors

The review is interesting due to its interdisciplinary approach, combining issues of phytochemistry, pharmacokinetics, and nanomedicine. Chemists gain fresh insights into how the structural features of flavonoids affect their encapsulation, pharmacists understand the challenges of overcoming low bioavailability, and oncologists learn about recent developments in nanoformulations that are effective in vivo.

Authors provided relevant overview of the major nanotechnological platforms used to overcome the bioavailability limitations of flavonoids, integrating mechanistic insights with practical formulation strategies in a well-structured manner.

A particular benefit of the review is its critical discussion of emerging translational challenges, including protein corona formation, scalability issues, and the integration of AI-driven approaches, which adds valuable perspective for future research in flavonoid-based nanomedicine.

The review is based on a well-selected set of research articles spanning from foundational early studies (e.g., Manach et al., 2005; Walle, 2004) to very recent advances published up to current year, providing a balanced temporal coverage of both the historical development of the bioavailability paradigm and current nanocarrier strategies.

The comparative analysis of advantages and limitations is thoroughly executed, and the issues of scalability, protein corona, and regulatory barriers are discussed. The material is useful for both academic researchers and drug development specialists.

The article can be published after revision:

-The review article discusses several key flavonoids (quercetin, apigenin, fisetin, luteolin, genistein, naringenin, EGCG), however, their chemical structures are not presented. Given that biological activity, solubility, self-association ability, and interaction with nanocarriers critically depend on structural features (the position of hydroxyl groups, the degree of unsaturation of the C-ring, the presence of glycosylation), the inclusion of a figure comparing the basic structures of the main flavonoid subclasses would significantly enhance the scientific and educational value of the manuscript.

-The introduction would benefit from a conceptual scheme to help understand how the sections of the manuscript are connected. For example, to link the flavonoid molecule, anticancer mechanisms, barriers (solubility, metabolism, efflux), nanocarriers (PLGA particle, liposome, micelle, cyclodextrin), and therapeutic outcome (tumor accumulation, apoptosis). The authors may consider titling such a figure «Overview of the main barriers to flavonoid oral bioavailability and the corresponding nanocarrier-based strategies to overcome them, guiding the structure of this review» or another title at their discretion.

-Sections 1–5 constitute an analytical literature review with elements of discussion: they compare data, draw conclusions, point out contradictions, and interpret research results. Section 6 is titled «Discussion», but in content it largely repeats and summarizes what has already been said, adding only a few new topics (scaling issues, protein corona, AI/ML, prospects). Therefore, I suggest that the authors consider renaming Section 6 to «Future perspectives: smart nanocarriers, AI/ML, and clinical translation».

-Please correct the typo Deliveryox (line 285).

-Not all abbreviations are expanded upon first mention. For enzymes and signaling pathways, a brief explanation is necessary, as the reader may not be familiar with molecular biology. This applies to terms such as phosphoinositide 3-kinase, protein kinase B, mammalian target of rapamycin, mitogen-activated protein kinase, and others.

-Please unify the references: make the year bold (refs 13, 15, etc.).

-References 54 and 56 are duplicated.

-Ref. 4: https://doi.org/10.3390/bioengineering9050197. Please check other references without a DOI.

Author Response

Comment:
“The review is interesting due to its interdisciplinary approach, combining issues of phytochemistry, pharmacokinetics, and nanomedicine.”

Response:
We sincerely thank the reviewer for the careful evaluation of our manuscript and for the highly positive and constructive comments. We greatly appreciate the recognition of the interdisciplinary nature of this review and its relevance for researchers working in medicinal chemistry, pharmacokinetics, nanotechnology, and oncology.

Comment:
“The review article discusses several key flavonoids (quercetin, apigenin, fisetin, luteolin, genistein, naringenin, EGCG), however, their chemical structures are not presented.”

Response:
We fully agree with the reviewer’s observation. To address this important point, a new figure presenting representative chemical structures of the principal flavonoid subclasses discussed throughout the review was incorporated into the manuscript (Figure 1). The figure includes quercetin, apigenin, fisetin, luteolin, EGCG, genistein, and naringenin, and was designed to emphasize structural differences relevant to biological activity, physicochemical behavior, and interaction with nanocarrier systems. The corresponding legend was also expanded to strengthen the medicinal chemistry perspective of the review.

Comment:
“The introduction would benefit from a conceptual scheme to help understand how the sections of the manuscript are connected.”

Response:
We sincerely appreciate this excellent suggestion. In response, a new conceptual schematic figure was incorporated into the Introduction section (Figure 3), illustrating the relationship between flavonoid structure, anticancer mechanisms, pharmacokinetic barriers (poor solubility, metabolism, efflux), nanocarrier-based delivery systems, and therapeutic outcomes. The figure was designed to improve the didactic organization and translational understanding of the manuscript structure.

Comment:
“I suggest that the authors consider renaming Section 6 to ‘Future perspectives: smart nanocarriers, AI/ML, and clinical translation’.”

Response:
We thank the reviewer for this insightful recommendation. Following the suggestion, Section 6 was renamed and substantially reorganized as “Comment:
“The review is interesting due to its interdisciplinary approach, combining issues of phytochemistry, pharmacokinetics, and nanomedicine.”

Response:
We sincerely thank the reviewer for the careful evaluation of our manuscript and for the highly positive and constructive comments. We greatly appreciate the recognition of the interdisciplinary nature of this review and its relevance for researchers working in medicinal chemistry, pharmacokinetics, nanotechnology, and oncology.

Comment:
“The review article discusses several key flavonoids (quercetin, apigenin, fisetin, luteolin, genistein, naringenin, EGCG), however, their chemical structures are not presented.”

Response:
We fully agree with the reviewer’s observation. To address this important point, a new figure presenting representative chemical structures of the principal flavonoid subclasses discussed throughout the review was incorporated into the manuscript (Figure 1). The figure includes quercetin, apigenin, fisetin, luteolin, EGCG, genistein, and naringenin, and was designed to emphasize structural differences relevant to biological activity, physicochemical behavior, and interaction with nanocarrier systems. The corresponding legend was also expanded to strengthen the medicinal chemistry perspective of the review.

Comment:
“The introduction would benefit from a conceptual scheme to help understand how the sections of the manuscript are connected.”

Response:
We sincerely appreciate this excellent suggestion. In response, a new conceptual schematic figure was incorporated (Figure 3), illustrating tWorkflow summarizing the literature search, screening, eligibility assessment, and study selection strategy adopted in this narrative review focusing on flavonoid-based nanocarrier systems for cancer therapy. In addition, the added Graphic Summary shows exactly how the sections of the manuscript are connected.

Comment:
“I suggest that the authors consider renaming Section 6 to ‘Future perspectives: smart nanocarriers, AI/ML, and clinical translation’.”

Response:
We thank the reviewer for this insightful recommendation. Following the suggestion, Section 6 was renamed and substantially reorganized as “Future Perspectives: Smart Nanocarriers, AI/ML, and Clinical Translation” in order to better reflect the content and translational focus of this section.

Comment:
“Please correct the typo Deliveryox (line 285).”

Response:
We appreciate the reviewer’s careful reading of the manuscript. The typographical error (“Deliveryox”) was corrected in the revised version.

Comment:
“Not all abbreviations are expanded upon first mention.”

Response:
We thank the reviewer for identifying this important issue. The manuscript was carefu

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed the reviewer comments. The manuscript is now suitable for publication.