Green Synthesis of Selenium Nanoparticles Using Cleistocalyx operculatus Leaf Extract and Their Acute Oral Toxicity Study
, Phuong Thi Mai Nguyen 2,3, Ngan Hanh Pham 4, Thanh Huu Le 1, Tran Hung Nguyen 1,*, Dinh Trung Do 5 and Duong Duc La 1,*Round 1
Reviewer 1 Report
The manuscript is an experimental study of the synthesis of Selenium nanoparticles using plant leaf extract (Cleistocalyx operculatus). The reaction products are characterized using UV-vis and FTIR sepctroscopy, as well as X-ray diffraction, and imaging by means of electron microscopy with energy dispersive elemental analysis. Then, the authors report a toxicity study using mice, as well as tests on the antimicrobial activity of these products.
As stressed in the introduction, biological ways of nanoparticle synthesis ('green synthesis') seem to be more effective in many respects compared to conventional physical and chemical methods. The topic is thus of considerable interest for the readers of 'Journal of Composite Science'.
I recommend publication after consideration of the following points:
1. The introduction is a little bit a hymn of praise to the 'green synthesis' of nanoparticles. Its effectiveness seems to be obvious in comparisson with physical approaches. Can the authors give an estimation, which amount of plant leaf extract is necessary to produce a certain amount of selenium nanoparticles? I think this information would be necessary if an industrial scale production of selenium nanoparticles by this method is envisaged. Moreover, a possible drawback of the green synthesis seems to me that the leaf extract could contain also impurities which could also aggregate in the nanoparticles or at their surface. Especially for medical applications this could be a crucial point.
2. Unfortunately, the manuscript lacks a discussion section. Is there a special reason, why Cleistocalyx operculatus leaf extract was chosen to react with the selenium precursors? Other studies of metal nanoparticle formation using other plant extracts can be found in literature (Jadoun, S., Arif, R., Jangid, N.K. et al. Green synthesis of nanoparticles using plant extracts: a review. Environ Chem Lett 19, 355–374 (2021). https://doi.org/10.1007/s10311-020-01074-x). So, is there some selectivity of Cleistocalyx operculatus leaf extract towards Se reduction and nanoparticle formation? In this context, the quality of the manuscript would be considerably improved if the authors would discuss the composition of the leaf extract in more detail. The amount of flavonoids and polyphenols is reported in the text (line 96), but their significance for nanoparticle formation is only mentioned in a rather general way. The composition of Cleistocalyx operculatus plant parts can be found in literature (see Giang Nam Pham, Tu Thanh Thi Nguyen, Hieu Nguyen-Ngoc, "Ethnopharmacology, Phytochemistry, and Pharmacology of Syzygium nervosum", Evidence-Based Complementary and Alternative Medicine, vol. 2020, Article ID 8263670, 14 pages, 2020. https://doi.org/10.1155/2020/8263670 and also Niranjan Koirala, Nguyen Huy Thuan, Gopal Prasad Ghimire, Duong Van Thang, Jae Kyung Sohng, Methylation of flavonoids: Chemical structures, bioactivities, progress and perspectives for biotechnological production, Enzyme and Microbial Technology 86 (2016) 103–116, https://doi.org/10.1016/j.enzmictec.2016.02.003)
According to these works, Cleistocalyx operculatus may contain significant amounts of C-methylated flavonoids and especially quercetin.
Minor points:
lines 33-36: Reference 8 reports nanoparticle synthesis by means of laser ablation and thus physical methods, not by chemical methods for which the authors use it as a proof. So this sentence seems to me a bit misleading.
line 265: '(data not show)' should read '(data not shown)').
Author Response
September 25, 2022
Journal of Composite Science
Re: Response on Manuscript ID jcs-1944016:
Thank you for considering our manuscript for publication in Journal of Composite Science. We are very grateful for such a good news about the status of our manuscript. We have revised the manuscript to address the concerns of reviewers and editorial office. The point-to-point address of all reviewers’ comments are presented below.
Hope you find revised manuscript suitable for publication in Journal of Composite Science.
We look forward to hearing from you in due course.
Yours sincerely
Dr. Duong Duc La
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Reviewer #1:
The introduction is a little bit a hymn of praise to the 'green synthesis' of nanoparticles. Its effectiveness seems to be obvious in comparisson with physical approaches. Can the authors give an estimation, which amount of plant leaf extract is necessary to produce a certain amount of selenium nanoparticles? I think this information would be necessary if an industrial scale production of selenium nanoparticles by this method is envisaged. Moreover, a possible drawback of the green synthesis seems to me that the leaf extract could contain also impurities which could also aggregate in the nanoparticles or at their surface. Especially for medical applications this could be a crucial point.
Response: Thank you very much indeed for the valuable comment. The required amount of plant leaf extract used for the synthesis of certain amount of selenium nanoparticles depends on the types pf plant, particularly the polyphenols content in that leaf extract. In case of Cleistocalyx operculatus leaf extract, with polyphenol content of around 12-14 %, the amount of concentrated CO extract for synthesis of 1 liter Se NPs 400 ppm was approximately 50 ml, equivalent to 100 g of dried CO leaf.
Furthermore, the biological properties of the CO extract have been well-studied by Prof. Nguyen’s group indicating the high antioxidant activity, biocompatible and biological safety. (PHUONG, Nguyen Thi Mai, BOGER, Christin, et ULRIKE, Lindequist. Cytotoxicity and antioxidant activity of plant extracts from Vietnam. Academia Journal of Biology, 2020, vol. 42, no 1.)
Unfortunately, the manuscript lacks a discussion section. Is there a special reason, why Cleistocalyx operculatus leaf extract was chosen to react with the selenium precursors? Other studies of metal nanoparticle formation using other plant extracts can be found in literature (Jadoun, S., Arif, R., Jangid, N.K. et al.Green synthesis of nanoparticles using plant extracts: a review. Environ Chem Lett19, 355–374 (2021). https://doi.org/10.1007/s10311-020-01074-x). So, is there some selectivity of Cleistocalyx operculatus leaf extract towards Se reduction and nanoparticle formation? In this context, the quality of the manuscript would be considerably improved if the authors would discuss the composition of the leaf extract in more detail. The amount of flavonoids and polyphenols is reported in the text (line 96), but their significance for nanoparticle formation is only mentioned in a rather general way. The composition of Cleistocalyx operculatus plant parts can be found in literature (see Giang Nam Pham, Tu Thanh Thi Nguyen, Hieu Nguyen-Ngoc, "Ethnopharmacology, Phytochemistry, and Pharmacology of Syzygium nervosum", Evidence-Based Complementary and Alternative Medicine, vol. 2020, Article ID 8263670, 14 pages, 2020. https://doi.org/10.1155/2020/8263670 and also Niranjan Koirala, Nguyen Huy Thuan, Gopal Prasad Ghimire, Duong Van Thang, Jae Kyung Sohng, Methylation of flavonoids: Chemical structures, bioactivities, progress and perspectives for biotechnological production, Enzyme and Microbial Technology 86 (2016) 103–116, https://doi.org/10.1016/j.enzmictec.2016.02.003)
According to these works, Cleistocalyx operculatus may contain significant amounts of C-methylated flavonoids and especially quercetin.
Response: Thank you very much indeed for the valuable comment. The discussion part in this work was integrated in the results and discussion part. Since the biological properties of the CO extract has been well-studied previously and this work only focused on the utilization of the CO extract for the synthesis of Se NPs with less detail of the composition investigation. However, more discussion on the reason why Cleistocalyx operculatus leaf extract was chosen to react with the selenium precursors was added in the manuscript such as the CO extract contains high content of polyphenols and flavonoids, which are the main reducing reagent for the reaction of selenium precursors; they also consist of useful polysaccharide content, which might protect newly formed Se NPs from oxidation. The selected references were added and discussed. Please see the yellow highlight in the manuscript.
Minor points:
- lines 33-36: Reference 8 reports nanoparticle synthesis by means of laser ablation and thus physical methods, not by chemical methods for which the authors use it as a proof. So this sentence seems to me a bit misleading.
Response: Thank you for the comment. The reference related to the chemical methods was also added in this sentence along with the physical method reference. Please see the yellow highlight in the manuscript.
- line 265: '(data not show)' should read '(data not shown)').
Response: Thanks. Done
Reviewer 2 Report
Duong Duc La and co-authors presented a work on Selenium NPs synthesis using Cleistocalux operculatus leaf extract. After mixing the extract with selenium dioxide, a change in the color of the solution was observed, which is explained by the authors by the formation of selenium nanoparticles (this was also previously confirmed by other authors). Further, the toxicity of this solution in mice and some biological tests were investigated. The main idea of the work is that the use of the prepared solution of NPs may be more successful for fetching selenium in living organisms, since the obtained samples were less toxic. The positive aspects of the work include a good description of the experiment and experimental data, a clear presentation of the material, and also an undoubted novelty. The manuscript is well written and requires minor language adjustments. I find this work possible for publication in Journal Composite Science, however authors are encouraged to answer some key questions before publication.
1. According to SEM images, the obtained particles are not individual, but are essentially aggregated into rather large objects. There can be quite a few reasons for this, and the authors give some, however, I cannot call these particles nanoparticles. I presume that the authors put their opinion and definition of NPs, so it makes sense to cite additional literary sources in the manuscript, where similar objects (with similar sizes and irregular shapes) are also classified as nanoparticles.
2. The introduction looks too big and blurry. It would be better to shorten the introduction, especially the part related to NPs. A lot has been done in nanochemistry, and the current work is not a review, so two or three key reviews on the use of NPs in medicine and biology would be enough.
3. Mapping and EDX analysis show that the analyzed particles consist not only of selenium, but also include oxygen and carbon. It is possible that carbon and oxygen are part of the polysaccharides that coat the selenium nanoparticles. In this case, it is necessary to wash off this coating to make sure that it is really polysaccharides. If no changes follow after washing, then this may be selenium oxide, the reduction of which has not occurred, and the color change is due to the formation of selenium complexes. In this case, the carbon signal may come from the support for microscopic studies. So, some clarifications are welcome.
Author Response
September 25, 2022
Journal of Composite Science
Re: Response on Manuscript ID jcs-1944016:
Thank you for considering our manuscript for publication in Journal of Composite Science. We are very grateful for such a good news about the status of our manuscript. We have revised the manuscript to address the concerns of reviewers and editorial office. The point-to-point address of all reviewers’ comments are presented below.
Hope you find revised manuscript suitable for publication in Journal of Composite Science.
We look forward to hearing from you in due course.
Yours sincerely
Dr. Duong Duc La
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Reviewer 2:
- According to SEM images, the obtained particles are not individual, but are essentially aggregated into rather large objects. There can be quite a few reasons for this, and the authors give some, however, I cannot call these particles nanoparticles. I presume that the authors put their opinion and definition of NPs, so it makes sense to cite additional literary sources in the manuscript, where similar objects (with similar sizes and irregular shapes) are also classified as nanoparticles.
Response: Thank you very much for your valuable comment. Since synthesis of Se NPs using the CO extract which contains polysaccharide compounds, which can be coated on the surface of newly form Se nanoparticles. When preparing for the SEM observation, the Se NPs-containing solution was drop-casted on the silicon wafer which might induce the aggregation of the Se NPs with organic coating on the surface. However, in the solution, Se NPs were highlight stable with no aggregation or precipitation was observed. Several works with similar morphologies called Se NPs were added to support the claim. Please see the yellow highlight in the manuscript.
- The introduction looks too big and blurry. It would be better to shorten the introduction, especially the part related to NPs. A lot has been done in nanochemistry, and the current work is not a review, so two or three key reviews on the use of NPs in medicine and biology would be enough.
Response: Thank you very much for the recommendation. The introduction was revised to be more concise and clear. Please see the yellow highlight in the manuscript.
- Mapping and EDX analysis show that the analyzed particles consist not only of selenium, but also include oxygen and carbon. It is possible that carbon and oxygen are part of the polysaccharides that coat the selenium nanoparticles. In this case, it is necessary to wash off this coating to make sure that it is really polysaccharides. If no changes follow after washing, then this may be selenium oxide, the reduction of which has not occurred, and the color change is due to the formation of selenium complexes. In this case, the carbon signal may come from the support for microscopic studies. So, some clarifications are welcome.
Response: Thank you very much for your valuable comment. It was experimentally evident that the pristine Se nanoparticles were facilely oxidized by the oxygen right after the coating was washed, especially during the measurement process. As for preparation of the XRD analysis, we had to wash the polysaccharide coating out of the Se NPs to obtain the better crystallinity. The resultant XRD pattern also revealed the presence of some Se oxide proportion. So, it would be similar for the EDX analysis, which the measuring process involving in some stages that Se NPs in the contact with the ambient conditions; as a result, it would be oxidized if no organic coating was observed.
Round 2
Reviewer 1 Report
I recommend acceptance of the revised manuscript.
Reviewer 2 Report
As I can see, the manuscript was improved, so, it can be published in Journal of Composite Science.
