Using Chitosan or Chitosan Derivatives in Cancer Therapy

Round 1

Reviewer 1 Report

The reviewer found the manuscript to look like a systematic review paper and found it interesting, too.  However, the following are the comments necessary to address:

(i) Reduction is necessary below 10% similarity reports on the submitted manuscript. 

(ii) A "Crosscheck" analysis of your paper indicates significant similarity with other published scientific papers.  I have looked at this carefully.  In many cases, whole paragraphs or significant word groupings were copied without appropriate citations.  Please carefully review and edit this paper to be sure you are fully attributing your sources.  Failure to do so can result in significant copyright issues and possibly charges of plagiarism.

(iii) Can authors include the separate subtitle of chitosan/surfactant used for cancer therapy?

(iv) The reviewer found less work on the application of chitosan emulsion Elaborate by providing separate subtitle.

(v) Conclusions need to rewrite by providing exact findings literature review.

(vi) English needs to improve throughout the manuscript.

Author Response

The reviewer found the manuscript to look like a systematic review paper and found it interesting, too.  However, the following are the comments necessary to address:

Response: We appreciate your optimistic feedback.

Point 1: Reduction is necessary below 10% similarity reports on the submitted manuscript. 

Response 1: Many thanks for your comment. We have revised the manuscript extensively. Similarity report is about 8% now. Additionally, similarity with any other document is not more than 1%. We feel this document will not face any copyright issue now. Thank you.

Point 2: A "Crosscheck" analysis of your paper indicates significant similarity with other published scientific papers.  I have looked at this carefully.  In many cases, whole paragraphs or significant word groupings were copied without appropriate citations.  Please carefully review and edit this paper to be sure you are fully attributing your sources.  Failure to do so can result in significant copyright issues and possibly charges of plagiarism.

Response 2: Many thanks for your comment. We have revised the manuscript extensively. Similarity report is about 8% now. Additionally, similarity with any other document is not more than 1%. We feel this document will not face any copyright issue now. Thank you.

Point 3: Can authors include the separate subtitle of chitosan/surfactant used for cancer therapy?

Response 3: We have included a separate section subtitled “Chitosan-based surfactant in cancer treatment” in the revised manuscript (Lines 586-610).We hope it’s alright now. Thank you.

Point 4: The reviewer found less work on the application of chitosan emulsion Elaborate by providing separate subtitle.

Response 4: In the revised manuscript, we have added information in section subtitled “Chitosan-based emulsion in cancer therapy” (Lines 611-656).We hope it’s alright now. Thank you.

Point 5: Conclusions need to rewrite by providing exact findings literature review.

Response 5: Many thanks for your suggestion. The conclusion section has been revised in the revised manuscript (Lines 842-856). We hope it’s alright now.

Point 6: English needs to improve throughout the manuscript

Response 6: Many thanks for your suggestion. A careful revision has been done throughout the revised manuscript to improve the English quality. We hope the revised manuscript is better readable now. Thank you.

Reviewer 2 Report

See atached file

Comments for author File: Comments.pdf

Author Response

Point 1: The introduction section must be improved. Authors have focused their attention on the use of
biopolymers as carriers. However, glycans and glycoconjugates, in general, have a significant role
as anti-cancer agents (Curr. Med. Chem. 2020, 27, 1206-1242). In my opinion, the continuous flow
of introduction should cover: cancer, glycans, biopolymers and then chitosan which can be applied
both against cancer and drug delivery system.

Response 1: Many thanks for your comment. We have added the role of glycan in the chitosan segment. We hope that it is well matched with the flow of introduction. Please see the line number 59-62.

Point 2. The chemical structure of chitosan (Figure 1) must take into account the degree of deacetylation
by including the corresponding molar fraction of GlcN (x) and GlcNAc (100-x) units.

Response 2: Many thanks for your comment. We have modified figure 1 legend accordingly (Lines 78-80).   

Point 3. The properties of chitosan and chitosan derivatives should include the rational role of (a)
molecular weight (Mw); (b) the importance of degree of deacetylation (DD) and also degree of
substitution (DS) for chitosan derivatives; (c) the role of pH and so on. On the other hand, chitosan
can be obtained from other non-marine sources. Therefore, chitosan is not strictly a marine-based
polysaccharide.

Response 3: Many thanks for your comment. In the revised manuscript, we have added the rational role of (i) molecular weight; (ii) the importance of degree of deacetylation (DD) and also degree of substitution (DS) for chitosan derivatives; (iii) the role of pH and so on.  Please see the line number 68-107. We hope the revised manuscript is alright now.

Point 4. Page 2, lines 73-74. The main drawback of the use of chitosan in biomedical applications is the
poor solubility in water or physiological conditions instead of alkaline conditions. Therefore, the
preparation of chitosan derivatives should afford water soluble chitosans thus increasing their
therapeutic properties.

Response 4: The mentioned lines has been rewritten accordingly (Lines 100-102).  Thank you.

Point 5. Page 2, lines 75-76. To avoid any misunderstanding, two kinds of substitutions should be
considered for chitosan: N- and O-substitution. Therefore, the different modifications can be
classified within these substitutions. For instance, reductive amination must be included in Nsubstitution. One of the most important modification of chitosan to obtain water-soluble
derivatives is the methylation of amino groups (N-quaternization) affording trimethylammonium
chitosan. This kind of reaction should be also considered.

Response 5: In the revised manuscript, we have addressed two kinds of substitutions and revised some part (Lines 102-107). Thank you.

Point 6. Page 2, lines 76-85. The modification of chitosan can be carried out not only with hydrophilic
groups. Some hydrophobic groups increase the capability to form hydrogels or other features as
fluorescent derivatives.

Response 6: We have revised this segment according to your comment 3, 4 and 5. We hope it’s alright now. Thank you.

Point 7. The statement “Alkylation and acylation both significantly diminish intermolecular hydrogen
linkages, resulting in a higher dissolution rate” (page 3, line 83) is superfluous. Firstly, the solubility
of chitosan strongly depends on its molecular weight. Secondly, the pH is a key factor to obtain a
solution of chitosan, for example, by protonation of amino groups. The presence of these charged
chitosan chains splits the hydrogen bonds between intermolecular chains (these intermolecular hydrogen bonds determine the crystalline structure). In a situation where hydroxyl and/or amino
group are acylated lead to a chitin like derivatives (depending of degree of N-substitution) thus reducing the solubility. What authors mean with dissolution rates? Authors should accurate describe the meaning of their statement.

Response 7:  We deleted this statement. Hope the revised segment is all right now. Please see the line number 99-107. Thanks

Point 8. Similarly, the statement “The anticancer activities of chitosan derivatives can be further
modified using different formulations” (page 3, line 90) also induces misunderstanding. Authors
should modify this sentence including more details. Are formulations used instead of reactions or
is referred to the additives and the final preparation of drugs containing chitosan? Please, clarify.

Response 8: Many thanks for your comment. We have modified the mentioned portion accordingly (Lines 112-113). 
Point 9. The abbreviation of sulphated benzaldehyde chitosan should be SBCS according to the original
reference.

Response 9: We have changed the abbreviated form in the revised manuscript. Please see the line number 138-226. Thank you.

Point 10. The section “anticancer activity of chitosan and its derivatives” should include chitosan
oligosaccharides (COS). In addition, authors should also focus their attention on how molecular
weight modify the antitumor activity of chitosan. In this context, some references (i.e. The Journal
of Nutrition, 2004, 134, 945-950) shows that the effect of 21 and 46 kDa is higher than chitosan of
120 kDa.

Response 10: Many thanks for your suggestion. In the revised manuscript, we have modified the “anticancer activity of chitosan and its derivatives” section by adding information regarding chitosan oligosaccharides (COS) (Lines 144-216). We have also cited the relevant reference for adding the relevant information. We hope it’s alright now. Thank you.

Point 11. IC50 values (Table 1) should display the same units for comparative purposes.

Response 11: We highly appreciate your valuable comment, as it can compare the potency of different chitosan derivatives. However, some of the reported studies did not mention the exact molecular weight, and in some cases it showed the range.  We are sorry to state that due to the varying molecular weight of chitosan, we couldn’t convert the unit. We hope your kind consideration in this regard. Thank you.

Point 12. For non-initiated readers, table 1 should include the cancer types instead of cell lines. These
cell lines must be added in parenthesis after the “cancer type” tag. The column “modified group”
should be removed. It may be preferred a column containing “active moiety” or something similar.

Response 12: Many thanks for your comment. In the revised manuscript, we have added a column containing cancer type in table 1. Thank you

Point 13. The units in table 1 should be homogenous within the manuscript. Therefore, units of CTC
(table 1) in g/mol must be modified accordingly.

Response 13:  We have corrected the units of CTC in the table. In the revised manuscript, the units in table 1 are homogenous now. Thank you.

 Point 14. Abbreviation of N/A and NR should be also added to the list below the table.

Response 14: The abbreviated form of N/A and NR has been added in the revised manuscript. Thank you.

Point 15. Page 4, line 9: “protonated amino groups” instead of “protonated amines”. Analogously in
lines 164-165

Response 15: The mentioned correction has been done in the revised manuscript (Line 291). Thank you.

Point 16. Carboxymethyl chitosan is an anionic water-soluble chitosan. Therefore, there is a mismatch
between its electronic nature and the strategy showed in Figure 2. Please clarify this point.
Similarly, data from reference 53 reveals that the employed biopolymer is close to chitosan
oligosaccharides instead a low molecular weight chitosans (with higher Mw values). In my opinion,
the frontier between low molecular weight chitosans and chitosan oligosaccharides (they are
intrinsically soluble in water) must be accurately defined.

Response 16: Many thanks for your comment. We completely agree with your comment that Carboxymethyl chitosan is an anionic water-soluble chitosan. But the chitosan-based complexes are associated cationic polymers which contributes to the resulting positive charge of the Carboxymethyl chitosan and polymer conjugated complex. Please see the line number 310-312. Thank you . 

Point 17. There are new references about this topic in the literature, therefore, the authors must check
and update the most significant references for a comprehensive review: Carbohydr. Res. 2021,
506, 108357; Nanomaterials 2021, 11, 2057; Carbohydr. Polym. 2021, 251, 117103, among others.

Response 17: Many thanks for your suggestions. The mentioned references have been included in the revised manuscripts (Reference No. 43, 50, 51). Thank you

Point 18. The use of chitosan in photodynamic therapy should be highly desirable in this review

Response 18: Many thanks for your suggestion. A new section regarding photodynamic therapy of chitosan has been included in the revised manuscript (Lines 414-460). Thank you.

Point 19. The conclusion section should be renamed as “Conclusions and future perspectives” since
authors finally included their opinion about the next directions on clinical trials.

Response 19: Many thanks for your suggestion. The conclusion section has been renamed accordingly in the revised manuscript. We hope it’s alright now. Thank you.