Evaluation of Membrane Permeability of Copper-Based Drugs

Round 1

Reviewer 1 Report

The manuscript by Jackson and coauthor is very well written and it is original work. After minor revision I suggest acceptance.

1. line 70-71 plese correct equation 1.

2. authors should include recent references

Author Response

Reviewer #1: The manuscript by Jackson and coauthor is very well written and it is original work. After minor revision I suggest acceptance.

1. line 70-71 please correct equation 1.
2. authors should include recent references

Equation 1 corrected.

References have been updated.

Reviewer 2 Report

In this study, authors used a Cerasome 9005 membrane to test the membrane permeability of copper. Various ligands were used to improve the diffusion of copper. However, all of these ligands were previously used copper drugs. The novelty of this study is not strong. The followings are some concerns about this study:  

1. The molecular interaction between ligands and copper is missing.  

2. The uptake of ions in cells is not depending on perfusion. The relationship between copper and anti-inflammation is not clear.

3. At least some in vitro cell studies should be conducted to verify the results from Cerasome 9005 membrane.

4. This reviewer did not find out any new or important information from this study.

Author Response

Reviewer #2: In this study, authors used a Cerasome 9005 membrane to test the membrane permeability of copper. Various ligands were used to improve the diffusion of copper. However, all of these ligands were previously used copper drugs. The novelty of this study is not strong.

As we state on line 56, the ligands used were specifically chosen because they had previously been studied as potential anti-inflammatory drugs.   The novelty in the work was not the compounds themselves but the measurement of their trans-membrane permeability.

 The followings are some concerns about this study:

1. The molecular interaction between ligands and copper is missing.

The solution structures of all the complexes used have been published and referenced in the manuscript.   Should the reviewer insist on these being reproduced here, a revised Figure 1 is supplied in which the structure of the complexes is given.   However, we feel that since the structures of the complexes are not discussed in this paper, the original figure is better.

2. The uptake of ions in cells is not depending on perfusion. The relationship between copper and anti-inflammation is not clear.

The introduction has been changed to add recent literature including a review on the role of copper, skin and inflammation.

3. At least some in vitro cell studies should be conducted to verify the results from Cerasome 9005 membrane.

Cerasome 9005 was chosen as the artificial membrane specifically because a 95% correlation was found between the permeability of it and porcine skin.

4. This reviewer did not find out any new or important information from this study

No comment.

Reviewer 3 Report

Kp is mentioned in line 56 for the first time but is never defined. Is K_p defined according to Fick's first law of diffusion? Though the use of K_p is now encouraged  (Journal of Scientific Research and Reports 3(22):2884-2899; doi:10.9734/JSRR/2014/13125) now criticized (Arch Toxicol. 2005 Mar;79(3):155-9; doi: 10.1007/s00204-004-0618-4), I would urge the Authors to define it.

The copper ion is referred to as copper(II), Cu⁺² and Cu(II). I strongly recommend to use the same symbol throughout the body text.

Though I fully agree with the Authors that ‘at the concentrations used, Cu(OH)₂ would precipitate at pH 7.00’, spending a couple of sentences explaining in detail  the reason for the choice of the pH value (4.23) used would only improve the quality of the paper.

Minor points

I guess there is a mistyping in equation 1.

Line 83. (K_ow) should be (K_o/w)

Line 98.  verses should be versus

Author Response

Reviewer #3:

 Kp is mentioned in line 56 for the first time but is never defined. Is K_p defined according to Fick's first law of diffusion? Though the use of K_p is now encouraged  (Journal of Scientific Research and Reports 3(22):2884-2899; doi:10.9734/JSRR/2014/13125) now criticized (Arch Toxicol. 2005 Mar;79(3):155-9; doi: 10.1007/s00204-004-0618-4), I would urge the Authors to define it.

Kp is defined in equation 3 according to Fick’s first law of diffusion and the two references suggested by the reviewer added.

The copper ion is referred to as copper(II), Cu⁺² and Cu(II). I strongly recommend to use the same symbol throughout the body text.

Same symbol Cu(II) has been used throughout.

Though I fully agree with the Authors that ‘at the concentrations used, Cu(OH)₂ would precipitate at pH 7.00’, spending a couple of sentences explaining in detail  the reason for the choice of the pH value (4.23) used would only improve the quality of the paper.

Sentence added – line 152.

Minor points

I guess there is a mistyping in equation 1.

Corrected

Line 83. (K_ow) should be (K_o/w)

Corrected

Line 98.  verses should be versus

Corrected

Reviewer 4 Report

I would like to recommend this manuscript for publication after minor revision:

1. Line 10, CuCl2, “2” should be subscript.

2. Figure 2, the data should be mean ± SD，n≥ 3

3. The format of the references is not satisfied the requirement of MDPI.

4. Does this study contribute to Cancer or inflammation treatment? If so , it is suggested to describe briefly in the Introduction combined with the suggested reference <Colorectal Cancer and Adjacent Normal Mucosa Differ in Apoptotic and Inflammatory Protein Expression, Engineered Regeneration 2 (2021) 279-287.>.

Author Response

I would like to recommend this manuscript for publication after minor revision:

1. Line 10, CuCl2, “2” should be subscript.

Corrected

2. Figure 2, the data should be mean ± SD，n≥ 3
   Figure 2 revised

3. The format of the references is not satisfied the requirement of MDPI.

To be corrected in final draft

4. Does this study contribute to Cancer or inflammation treatment? If so , it is suggested to describe briefly in the Introduction combined with the suggested reference <Colorectal Cancer and Adjacent Normal Mucosa Differ in Apoptotic and Inflammatory Protein Expression, Engineered Regeneration 2 (2021) 279-287.>.

We thank the review for this suggestion.   We have read the cited reference, and while it is very interesting, we feel that adding the possibility of cancer treatment is beyond the scope of the current paper.

Round 2

Reviewer 2 Report

The authors have provided some explanation about previous comments. I have no further questions.