Modification of Polyacrylonitrile Fibers by Coupling to Thiosemicarbazones

Round 1

Reviewer 1 Report

The paper by Yao describes thiosemicarbazone compounds and their biological activity. Overall, the article presents well-documented experiments and valuable findings, however:

In my opinion, the antibacterial sensitivity of the samples should be shown not only as Figures (Fig. 9), but also expressed as diameter of zone of inhibition.  The binding mode of molecule to metal ion cannot be obtained only from potentiometric titration (It was stated that the binding mode of the thiosemicarbazone compounds to the metal ion can be simulated by potentiometric titration experiments). Using a sole method is not enough to confirm the binding mode. A broad spectrum of experimental methods, eg. UV-Vis, CD, EPR, NMR, X-ray should be used to confirm the coordination pattern. Potentiometry gives only the information about proton dissociation (which doesn't have to be involved in metal ion binding) and the stoichiometry of the forming complex, but not about binding mode. 

Author Response

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Reviewer 2 Report

The manuscript ‘Modification of polyacrylonitrile fibers by coupling to thiosemicarbazones’ by Yao Yao et. al., is an interesting paper where the authors investigate the capability of their grafting approach to modifying PAN fibers, and their biological activity after modification.

The manuscript is well written and well-articulated, and it is proposed as neat and interesting strategy for the modification of PAN fibers. The mechanical property analysis though does not show a statistically significant difference between the original fibers and the modified ones. The error bars in all three samples (original, hydrolysed and modified) do overlap, not giving enough indications on the role of the modification to the mechanical properties of the fibers.

Also, in the FTIR analysis, which is the only characterisation technique used to investigating the effectiveness of the covalent coupling, the author indicates the presence of the peak at 1541 cm-1 as indicative of the presence of amine II. I would be careful with this attribution since it could be attributed to water content as well, specifically the bending at around 1590 cm-1. I would recommend another characterisation technique, such as XPS to cross check the efficacy of the covalent coupling.

Author Response

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Reviewer 3 Report

The authors reported on the preparation of thiosemicarbazones and their coupling with polyacrylonitrile fibers to obtain materials with biological activity.

The presentation of the work in the title/abstract is misleading as the majority of the work is conducted on the thiosemicarbazones alone, and only one attempt of coupling to the fibers is reported, with limited characterization on the biological activity. For example, cytotoxicity, ion chelation and the tyrosinase inhibition of the fibers are never demonstrated. Moreover, the chemistry of the whole paper raises some concerns. Major issue will be addressed in a point to point fashion. A deep revision of the work is suggested, before it is considered for publication.

Line 69: some of the characterization methods are described in the materials paragraph and should be moved.

Line 74: the authors referred to a literature procedure for the synthesis of thiosemicarbazones, but the paper they cite doesn’t contain such procedure (it cites another paper and both procedures are significantly different). The authors should detail their own procedure better and check their references (for example with catalyst amount, given that no catalyst is used in the paper they cite).

Line 120: the author used ethylene glycol as a solvent for grafting reaction. This could be participating in the condensation reaction in place of the thiosemicarbazone. The authors didn’t provide any convincing proof that the modification of the fibers is preferentially by the thiosemicarbazone (the FTIR they showed is compatible with the reaction with ethylene glycol too). Moreover, they state they used half a mole (about 107g) of DCC that is probably a mistake.

Line 276: the grafting efficiency determined only gravimetrically can be affected by several error, especially in case of grafting as low as 1.9%.

Line 281: table 3 is missing

Line 282: the authors performed mechanical testing of the fibers, that resulted in substantially unmodified breaking strength (Figure 7) while elongation at break is not reported. The data shown don’t justify any of the claim made through the paragraph about loss of mechanical resistance in the hydrolysis process and recover of such resistance by covering the fiber with the coating.  

Line 319: the author admitted they found OH at the surface, but never recognize that they could have linked ethylene glycol to the surface, instead of thiosemicarbazone. Moreover, I think this FTIR could be taken in ATR FTIR. If this is the case that should be stated.

Line 330: the antibacterial activity is poorly reported. By the image only is not clear enough the difference between PAN and PAN modified fiber, because it seems that the unmodified PAN also shows a significant antibacterial activity, maybe comparable to the modified fibers.

Line 346. The authors again claim anti tyrosinase activity of the fibers, that is never directly demonstrated.

Author Response

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Round 2

Reviewer 3 Report

the authors added new pertinent data and addressed all the comments. I believe the paper now is in a better form to be published, but I still feel that there is a little misleading presentation of the conclusion (and consequently the abstract, even if it was rephrased). As the authors write in their response, they speculated about the modified fiber retaining the activity of thiosemicarbazones free molecules, without giving enough direct evidence. Probably they should use the same caution in the paper when they affirm that the material possess certain properties.

 

 

 

Author Response

The main corrections in the paper and the response to the reviewer’s comments are as flowing:

The authors added new pertinent data and addressed all the comments. I believe the paper now is in a better form to be published, but I still feel that there is a little misleading presentation of the conclusion (and consequently the abstract, even if it was rephrased). As the authors write in their response, they speculated about the modified fiber retaining the activity of thiosemicarbazones free molecules, without giving enough direct evidence. Probably they should use the same caution in the paper when they affirm that the material possesses certain properties.

Response: We are very sorry for providing a misleading Conclusion and Abstract in the manuscript. However, as per your suggestion, we have modified the Abstract and Conclusion as per the results obtained evidently. We hope that the corrections will meet with final approval.

Once again, thank you very much for your comments and suggestions

Author Response File: Author Response.docx