Characterization of a Novel Packaged Hydrogel Wound Dressing by 2.35 T Magnetic Resonance Imaging

Round 1

Reviewer 1 Report

The manuscript "Characterization of a novel packaged hydrogel wound dressing by 2.35 T Magnetic Resonance Imaging" deals with the production and characterization of a novel packed hydrogel wound dressing by 2.35 T magnetic resonance imaging. The paper is well organized and well written, covering the most significant topics in the field. However, there are several changes authors should make before the manuscript can be accepted for publication:

Abstract: The quantitative results are completely missing in the abstract. The authors are advised to describe some quantitative results in order to enhance the readability of the article.

Avoid abbreviations before giving their explanation in abstract, main text, figure, and table.

Introduction: The authors are advised to include the advantages of wound dressings and magnetic resonance imaging in introduction section. The authors are also advised to discuss the following literature about wound management:

Artificial Cells Nanomed. Biotechnol. 45: 591-597 (2017); J. Oleo Sci. 67: 957-968 (2018); 3 Biotech. 9: 82 (2018).

Materials: The authors are advised to include city and country of location for each supplier.

Methods: The authors are advised to include suitable literature for each experimental procedure used.

Authors should briefly comment on the disadvantages of the studied systems. One whole paragraph should be added to let readers get better insight into the subject.

The authors should suggest, based on this article, an area of ​​research or space that still needs to be worked on.

Figure 6: The letters are not readable. Please enhance the resolution and quality of this figure.

Figure 7: Kindly include error bars in the graph. Also mention the number of replicates in figure caption.

Section 5: The sections discussion and conclusion should be separate part. Kindly discuss the results in the light of previous literature.

Conclusion: The conclusion should be concise and to the point indicating the application of the work.

Author Response

Referee: The manuscript "Characterization of a novel packaged hydrogel wound dressing by 2.35 T Magnetic Resonance Imaging" deals with the production and characterization of a novel packed hydrogel wound dressing by 2.35 T magnetic resonance imaging. The paper is well organized and well written, covering the most significant topics in the field. However, there are several changes authors should make before the manuscript can be accepted for publication:

Authors: We thank the Referee for her/his appreciation of our work.

Referee: Abstract: The quantitative results are completely missing in the abstract. The authors are advised to describe some quantitative results in order to enhance the readability of the article.

Authors: We thank the Referee for her/his comment. We added in the abstract the most relevant quantitative results (i.e. proton density, swelling and apparent diffusion coefficient) for the new hydrogel formulation and the standard commercial product (Neoheal®) taken as a reference.

Referee: Avoid abbreviations before giving their explanation in abstract, main text, figure, and table.

Authors: We thank the Referee for her/his comment. We carefully read the text and all abbreviations are defined before their use.

Referee: Introduction: The authors are advised to include the advantages of wound dressings and magnetic resonance imaging in introduction section. The authors are also advised to discuss the following literature about wound management:  Artificial Cells Nanomed. Biotechnol. 45: 591-597 (2017); J. Oleo Sci. 67: 957-968 (2018); 3 Biotech. 9: 82 (2018).

Authors: We added the suggested literature in the Introduction Section. Moreover, the following sentence and additional references were inserted in the Introduction section (page 2, lines 74-96).

“A significant body of previous work has shown several advantages of MRI for the characterization of hydrogels-based biomaterials and wound dressing, this due to the non-invasive and non-destructive insight into the chemical-physical properties and safety issues as well [40]. MRI of inhomogeneous calcium alginate gel samples allowed to successfully follow the spatial variation of alginate concentration and the distribution of pore size [41]. Moreover, MRI tracked the variation of the reaction front over the gelation process of sodium alginate by means of calcium ions [42]. It was reported that MRI is a useful tool to characterize the structures of calcium alginate gels of various compositions, thus providing an insight into the correlation between gels chemical structure and physical properties (mechanical gel strength, porosity, and water diffusion properties). Interestingly, it was argued that the mechanical properties of hydrogels, such as the modulus of rigidity, correlates with the water transverse relaxation time [43]. Alginate hydrogels beads encapsulating cells have been used for the purpose of cell transplantation. However, their usefulness depends on the ability to maintain structural integrity for sufficient periods of time. MRI successfully monitored the temporal changes in the structure of hydrogels beads layered with poly-L-lysine over a month culture, highlighting that this non-invasive imaging method provides valuable information about beads integrity [44]. The biocompatibility of hydrogel-based contact lenses, known to be closely related to their oxygen permeability, was studied by means of Nuclear Magnetic Resonance (NMR), showing that the water self-diffusion coefficient is a measure of the diffusive contribution to oxygen permeability [45]. Silver-containing wound dressings are gaining a more widespread use in the clinical practice. 3 T MRI was used with a wide series of standard pulse sequences to assess the safe use of such dressings [46-47].”

40. Mathur, A.M.; AB Scranton, A.B. Characterization of hydrogels using nuclear magnetic resonance spectroscopy. Biomaterials 1996, 17, 547-557. [https://doi.org/10.1016/0142-9612(96)88705-9]
41. Potter, K.; Carpenter, T.A.; Hall, L.D. Mapping of the spatial variation in alginate concentration in calcium alginate gels by magnetic resonance imaging (MRI). Res 1993, 246, 43–49. [https://doi.org/10.1016/0008-6215(93)84022-X]
42. Potter, K.; Balcom, B.J.; Carpenter, T.A.;Hall, L.D. The gelation of sodium alginate with calcium ions studied by magnetic resonance imaging (MRI). Carbohydr. 1994, 257,117–126. [https://doi.org/10.1016/0008-6215(94)84112-8]
43. Degrassi, A.; Toffanin, R.; Paoletti, S.; Hall, L.D. A better understanding of the properties of alginate solutions and gels by quantitative magnetic resonance imaging (MRI). Carbohydr. 1998, 306,19–2620. [https://doi.org/10.1016/S0008-6215(97)10054-4]
44. Grant, S.C.; Celper, S.; Gauffin-Holmberg, I.; Simpson, N.E.; Blackband, S.J.; Constantinidis, I. Alginate assessment by NMR microscopy, Journal of Materials Science: Materials in Medicine 2005, 16, 511– 514. [https://doi.org/10.1007/s10856-005-0525-0]
45. Manetti, C.; Casciani, L.; Pescosolido, N. Diffusive contribution to permeation of hydrogel contact lenses: theoretical model and experimental evaluation by nuclear magnetic resonance techniques. Polymer 2002, 43, 87-92. [https://doi.org/10.1016/S0032-3861(01)00559-6]
46. Chaudhry, Z.; Sammet, S.; Coffey, R.; Crockett, A.; Yuh, W.T.C.; Miller, S. Assessing the safety and compatibility of silver based wound dressings in a magnetic resonance environment. Burns 2009, 35, 1080-1085. [https://doi.org/10.1016/j.burns.2009.02.014]
47. Bailey, J.K.; Sammet, S.; Overocker, J.; Craft-Coffman, B.; Acevedo, C.M.; Cowan, M.E.; Powell, H.M. MRI compatibility of silver based wound dressings. Burns 2018, 44, 1940-1946. [https://doi.org/10.1016/j.burns.2018.05.017]

Referee: Materials: The authors are advised to include city and country of location for each supplier.

Authors: Done.

Referee: Methods: The authors are advised to include suitable literature for each experimental procedure used.

Authors: Done.

Referee: Authors should briefly comment on the disadvantages of the studied systems. One whole paragraph should be added to let readers get better insight into the subject.

Authors: As suggested by the referee the following sentence was inserted in the revised manuscript (page 14, lines 462-466):

“We observed that the commercial hydrogel [20] presents a larger water proton density and a higher swelling capacity, despite a smaller water mobility and reduced mechanical properties while extracted from the package. On the contrary, the novel hydrogel [49] can retain less water, present a higher water mobility and a smaller swelling degree, while showing improved mechanical strength during manipulation.”

Referee: The authors should suggest, based on this article, an area of ​​research or space that still needs to be worked on.

Authors: As suggested by the referee the following sentence was inserted in the revised manuscript (page 14, line 478-480):

“Finally, based on our current findings, we can envisage the following future work to better compare the standard and novel hydrogel dressing materials: microscopic characterization (SEM, TEM, AFM); mechanical tests; swelling measurements; high resolution NMR spectroscopy.”

Referee: Figure 6: The letters are not readable. Please enhance the resolution and quality of this figure.

Authors: We improved the axes labels readability.

Referee: Figure 7: Kindly include error bars in the graph. Also mention the number of replicates in figure caption.

Authors: As suggested we updated the plot of Fig. 7 and the caption including the errors defined as the standard error of the mean from two replicated measurements.

Referee: Section 5: The sections discussion and conclusion should be separate part. Kindly discuss the results in the light of previous literature.

Authors: As suggested by the referee the Discussion and Conclusion sections were separated.

To clarify the significance of our results with respect to the previous literature, the following sentence was inserted in section Discussion (page 13, lines 416-420).

“To the best of our knowledge, the MRI characterization of the novel hydrogel (S6) and its comparison with the previously known hydrogels (S1, S4) was not reported before. So, unfortunately, a direct comparison of our MRI results with the previous literature is not possible. In the following we discuss the results in view of the mutual 2.35 T MRI properties between the hydrogel compositions reported in Table 2.”

Referee: Section Conclusion: The conclusion should be concise and to the point indicating the application of the work.

Authors: As suggested by the Referee the Conclusion section was made concise. Moreover, to better point out the final applications of our work, the original sentence reported at pag. 13 lines 417-418, was modified as follows (page 14, lines 467-471) and a reference added:

“We believe our quantitative MRI methodology may find useful applications in the chemical-physical characterization of a wide class of hydrogel-based wound dressing and in optimizing their industrial production processes. Moreover, the MRI hydrogel characterization reported here could find useful clinical applications in the use of hydrogels as water bolus during hyperthermia treatments for improving heat delivery [62].”

[62] Trefná HD, Ström A. Hydrogels as a water bolus during hyperthermia treatment. Phys Med Biol. 2019 May 31;64(11):115025. doi: 10.1088/1361-6560/ab0c29.

Reviewer 2 Report

This manuscript reported the preparation of novel packaged hydrogel with calcium alginate, agar and polyvinylpyrrolidone as well as gamma irradiation. The physical crosslinking betweeen the Ca2+ ions and alginate in combination with chemical crosslinking by gamma irradiation enhances the properties of the hydrogels. They also apply the hydrogels in wood dressing materials and Magnetic Resonance Imaging (MRI) was applied to characterize the relaxation times and diffusion coefficient of water. The preparation method dominates the properties of the hydrogels. This manuscript needs some revisions, and some suggestions were listed below for the improvement of this manuscript  

1. Why citing paper in the description of a sentence, page9, line314, and page10, line 318?

2. The variations between S1 and S2 is caused by hydrophilicity not ionic charges.

3. How about the swelling properties of other properties?

4. What’s the mechanical properties and PRESS spectra of the hydrogels?

5. Some important papers about the application of hydrogels are missing (Polymer, 2016, 85: 67-76, Aggregate, 2021, 2(2): e21 and Langmuir, 2017, 33(24): 6092-6101).

Author Response

Referee: This manuscript reported the preparation of novel packaged hydrogel with calcium alginate, agar and polyvinylpyrrolidone as well as gamma irradiation. The physical crosslinking betweeen the Ca2+ ions and alginate in combination with chemical crosslinking by gamma irradiation enhances the properties of the hydrogels. They also apply the hydrogels in wood dressing materials and Magnetic Resonance Imaging (MRI) was applied to characterize the relaxation times and diffusion coefficient of water. The preparation method dominates the properties of the hydrogels. This manuscript needs some revisions, and some suggestions were listed below for the improvement of this manuscript.

Authors: We thank the Referee for her/his appreciation of our work about the connection between the hydrogel properties as measured by MRI and the preparation methods.

Referee: 1. Why citing paper in the description of a sentence, page9, line314, and page10, line 318?

Authors: As suggested by the Referee, both citations have been removed.

Referee: 2. The variations between S1 and S2 is caused by hydrophilicity not ionic charges.

Authors: We thank the Referee for noting our error. We corrected the text accordingly to her/his suggestion.

Referee: 3. How about the swelling properties of other properties?

Authors: In this work we have limited the swelling measurement for the commercial (S1, S2) and the novel (S6) hydrogels, representative, respectively, of the chemical and chemical-physical crosslinking processes.

To clarify this, the following sentence was inserted at pag. 14 lines 446-448:

“In this work we report the swelling characterization for the commercial (S1, S2) and the novel (S6) hydrogels only, representative, respectively, of the chemical and chemical-physical crosslinking processes.”

Referee: 4 . What’s the mechanical properties and PRESS spectra of the hydrogels?

Authors: We thank the Referee for pointing out this issue. To clarify the role of mechanical properties and PRESS spectra, the sentence at pag. 10 line 364-365 of the original manuscript was removed and the following sentence was inserted at pag. 13 lines 436-445:

“From the localized PRESS spectra of the hydrogels S1, S4, S5, S6 reported in Fig. 6, we observe that the commercial hydrogel S1 presents a symmetrical and narrow line (0.7 ppm), while the novel hydrogel S6 shows an asymmetrical line with a relatively large bandwidth (1.5 ppm), like the compositions S4 (1.6 ppm) and S5 (1.4 ppm). Although the limited spatial resolution of the PRESS spectra reported here, we can observe that the larger bandwidth of the samples S4, S5, S6 is associated to their shared feature, i.e. the presence of the crosslinked calcium alginate hydrogel network. The future use of high-field NMR spectroscopy on the current hydrogel samples will allow a much better spectral resolution needed to better understand the nature of the spectral components underlaying the chemical-physical properties of the hydrogels compositions [40, 59-61].”

Referee: 5. Some important papers about the application of hydrogels are missing (Polymer, 2016, 85: 67-76, Aggregate, 2021, 2(2): e21, Langmuir, 2017, 33(24): 6092-6101).

Authors: As suggested the literature was inserted in the Introduction Section.

Reviewer 3 Report

The authors have made an interesting article describing a novel packaged hydrogel wound dressing. Here are some suggestions for improving the paper:

1. Please replace the words reticulation with crosslinking and reticulated with crosslinked.

2. Please correct line 44: sulphonated = sulfonated

3. Was distilled or deionized water used? Because both versions can be found in the article? Please correct the text.

4. Row 268, the formula for swelling measurements, please be in percentages (%) and add a reference.

Author Response

Referee: The authors have made an interesting article describing a novel packaged hydrogel wound dressing. Here are some suggestions for improving the paper:

Authors: We thank the Referee for her/his appreciation of our work.

Referee: 1. Please replace the words reticulation with crosslinking and reticulated with crosslinked.

Authors: Done. Because of this replacement the previous abbreviation “reticulated calcium alginate hydrogel (RAL)” was substituted by “crosslinked calcium alginate hydrogel (CAL)”.

Referee: 2. Please correct line 44: sulphonated = sulfonated

Authors: Done. Thanks.

Referee: 3. Was distilled or deionized water used? Because both versions can be found in the article? Please correct the text. 

Authors: We thank the Referee for her/his careful reading. We clarified through the manuscript that deionized water was used for samples’ preparation and distilled water for the swelling measurements.

Referee: 4. Row 268, the formula for swelling measurements, please be in percentages (%) and add a reference.

Authors: As suggested we modified the manuscript accordingly (page 8, line 292 of the revised manuscript) and a relevant reference [54] was inserted.

Round 2

Reviewer 1 Report

The authors have addressed the previous concerns. The revised manuscript is suitable for publication in its present form.