Ιnclusion Complexes of Magnesium Phthalocyanine with Cyclodextrins as Potential Photosensitizing Agents
and Anastasia Detsi 1,*Round 1
Reviewer 1 Report
The reviewed paper presents the preparation of inclusion complexes (IC) of natural (β-CD, γ-CD) and modified cyclodextrins (HP-β-CD, Me-β-CD) with magnesium phthalocyanine (MgPc) by kneading. According to the authors, MgPc encapsulation was obtained with very satisfactory inclusion efficiency values of 81%, 97%, 67% and 59% for β-CD-MgPc, HP-β-CD-MgPc, γ-CD-MgPc and Me-β-CD-MgPc IC, appropriately. The average size of the inclusion complexes (ICs) ranged from 564 to 748 nm, while the zeta potential ranged from -15 to -30 mV, indicating different stability of the formed ICs.
Inclusion complexes were typically described by FT-IR spectroscopy and 1H NMR spectroscopy. The IC stoichiometry determined by continuous variation in each case was 2 : 1 (CD : MgPc). Regarding the MgPc release test at 37°C in a pH 7.4 buffer solution, a bursting effect occurred during the first 20 minutes during which approximately 70% of the encapsulated MgPc was released. In vitro release from the nanosystems was found to follow Korsmeyer-Peppas kinetics, while the release mechanism is described as anomalous transfer. The ICs were tested for their ability to produce ROS, showing satisfactory ROS production after irradiation with a 661 nm laser. Photodynamic therapy studies against the A431 squamous cell carcinoma cell line showed a strong photosensitizing effect of MgPc (33% cell viability after 3 min irradiation of 18 mW/cm2), as well as IC γ-CD-MgPc, which was the most promising photosensitizing nanosystem showing the best PDT activity (cell viability 26% after 3 minutes of irradiation). Finally, intracellular localization studies showed cellular uptake of MgPc after incubation of the cells with the γ-CD-MgPc complex for 4 hours. Overall, the obtained ICs can be considered promising for sustained release of MgPc and effective PDT therapy of cancer.
Nevertheless, I believe that the publication needs to be supplemented and cannot be accepted in this form. Authors should perform the following studies:
In terms of synthesis, compare the products obtained by simply mixing the guest with the host. This process is also carried out in a mortar by kneading for several minutes in solvent-free conditions.
Attempts to synthesize complexes by precipitation, in which water is the main solvent, enabling the separation of the complex from the raw materials.
Compare the FTIR spectra of products obtained by different techniques.
The assessment of the inclusion complex formation cannot be made based on such subtle changes in the FTIR and 1H NMR spectra presented by the authors.
NMR studies must be supplemented with ROESY and DOSY measurements, which will unambiguously determine the type of interactions.
In the case of ROESY, the authors will see whether the MGPc molecule actually partially penetrates inside the CD torus or not. In my opinion, sandwich complexes are most likely formed in the stabilization of which CD hydroxyl groups located outside the cavities are involved.
DOSY measurements will make it possible to assess the stability of the resulting complexes as well as the existence of other equilibria. They will make it possible to determine the stability constants of the complexes.
Author Response
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Reviewer 2 Report
Generally, the proposed manuscript is well-organized and can be published as it is.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Recommendation: Minor revision
Comments:
In the manuscript entitled "Ιnclusion complexes of magnesium phthalocyanine with cyclodextrins as potential photosensitizing agents", Anastasia Detsi et. al., reported the preparation of inclusion complexes (ICs) using magnesium phthalocyanine (MgPc) and various cyclodextrins (β-CD, γ-CD, HP-β-CD, Me-β-CD) using the kneading method. The photodynamic therapy studies against squamous carcinoma A431 cell line indicated a potent photosensitizing activity of MgPC (33% cell viability after irradiation for 3 min with 18 mW/cm2), while the ICs also presented significant activity (γ-CD-MgPc: cell viability 26% after 3 min of irradiation). The results are convinced enough to support their point of view. There are some minor issues that the authors need to be considered while revising the manuscript. Thus, I would recommend this manuscript for publication after following modifications.
1. Abstract can be rewritten.
2. How inclusion complexes are different from the complexes.
3. Can the authors elaborate the experimental part of the light toxicity studies?
4. The authors can draw a 1:2 complex formation in the SI as per Job’s plot.
5. Remove the term “Job’s plot” from the inset of Figure 2.
6. The FT-IR stretching can be compared with the reference “Dalton Trans., 2022, 51, 3937-3953” and “10.1016/j.jcat.2020.06.005”
7. Figure 3 can be modified.
8. The colour combination in Figure 5 can be changed.
9. The baseline in Figure 6 should be uniform.
10. The cytotoxicity results can be compared with some recent references e.g., ACS Appl. Bio Mater. 2022, 5, 1, 190–204, Dalton Trans., 2020,49, 15481-15503, 10.1016/j.ccr.2021.214169
11. A scale bar should be added in Figure 10.
12. Conclusion part can be rewritten.
13. It can be observed throughout the manuscript that there are some missing spaces between two consecutive words. The authors need to be careful while resubmitting the manuscript.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The lack of two-dimensional NMR spectra leaves a certain unsatisfactory. The changes in the shapes of the multiplets of the aromatic part of the 1H NMR spectrum speak in favor of the formation of the complex. Unfortunately, it cannot be ruled out that they are caused not by inclusion but by other factors. However, due to the impossibility of supplementing the research with the above-mentioned ones due to the inoperative apparatus, I leave the editor's decision to accept or reject the publication.
