Green Synthesis of Magnesium Oxide Nanoparticles and Nanocomposites for Photocatalytic Antimicrobial, Antibiofilm and Antifungal Applications

Round 1

Reviewer 1 Report

In my opinion this is an interesting review in respect to information about green synthesis of magnesium oxide nanoparticles and their application.

However, I just have a few minor suggestions:

1) In introduction: “Nanomaterials are commonly synthesized utilizing a variety of chemical and physical processes that necessitate high temperatures, chemical additives, sophisticated instruments, and vacuum conditions [13,14]” – please give one or two example of method used to nanomaterials synthesis.  

2) In introduction: “Present advances in chemical techniques for the preparation of nanomaterials have raised biological dangers to the environment on account of the utilization of poisonous chemicals that remain adherent to synthesized nanomaterials” – please give some examples of these chemicals.

3) Authors sometimes write Gram-negative and Gram-positive (with a capital letter) and sometimes gram-negative, gram-positive (with a small letter) please standardize.

 

4) Please improve the quality of the Figures 5-7, they are too small and hard to see.

Author Response

Reviewer 1:

In my opinion this is an interesting review in respect to information about green synthesis of magnesium oxide nanoparticles and their application.

However, I just have a few minor suggestions:

1) In introduction: “Nanomaterials are commonly synthesized utilizing a variety of chemical and physical processes that necessitate high temperatures, chemical additives, sophisticated instruments, and vacuum conditions [13,14]” – please give one or two example of method used to nanomaterials synthesis.  

Response:

Thanks for this comment, some examples of nanomaterials synthesis method added to the mentioned part.

2) In introduction: “Present advances in chemical techniques for the preparation of nanomaterials have raised biological dangers to the environment on account of the utilization of poisonous chemicals that remain adherent to synthesized nanomaterials” – please give some examples of these chemicals.

Response:

To follow up on this comment, some examples have been provided in the introduction section.

3) Authors sometimes write Gram-negative and Gram-positive (with a capital letter) and sometimes gram-negative, gram-positive (with a small letter) please standardize.

Response:

Thanks for pointing this out, the words are standardized.

 4) Please improve the quality of the Figures 5-7, they are too small and hard to see.

Response:

Thanks for reviewer's attention. The quality of the images have been improved and some figures resized.

Reviewer 2 Report

This manuscript introduced the biosynthetic methods of MgO NPs are in three general ways based on plants, fungi and algae. The characteristic was detailed demonstrated, which mainly depend on the metabolites produced by biological material and their extracts, causing capping and stabilization for the particles and thus the formation of NPs. The superiority of biocompatible and environmentally friendly is fully utilized in a suitable approach for biological applications. The antibacterial mechanism of these NPs is mainly related to ROS and the destruction of the cell wall or membrane, although other processes such as electrostatic interaction and physical damage are also effective factors in applications of photocatalytic treatment. In general, this review of MgO NPs as biocompatible and eco-friendly material is a good guidance for biomedical applications. However, this paper is not suitable for publication in this form, which needs to be improved in light of the recommendations mentioned below.

Some major concerns are shown as following:

1.      Bio-templates-mediated synthesis strategies: This part lack of summary and analysis for plant extracts, bacterial extracts, fungi extracts, and algae extracts. Obvious research results cannot convey the critical meaning for this review, and the distinction and commonality should be described in this section.

2.      Applications of photocatalytic treatment: The potential application of MgO NPs activity against microbial, biofilm, and fungal should be summarized attributed to the different mechanisms. According to the content, the views and comments of authors should be expressed.

3.      In this manuscript, the introduction should be restructured since it is considered too simple. Some related work should be reviewed in this part, for example: Catalysts, 2021, 11(7), 821; Advanced Fiber Materials, 2022, 4, 119; Industrial Crops and Products, 2022, 187, 115442; Composites Communications, 2022, 34, 101271. Additionally, the reason why the authors selected this point, the interaction of different performance and application should be added in the manuscript.

4. Page 11 Line 305: The “2.1. Algae extracts” should be amended to “2.4. Algae extracts”.

Author Response

Reviewer 2:

 

This manuscript introduced the biosynthetic methods of MgO NPs are in three general ways based on plants, fungi and algae. The characteristic was detailed demonstrated, which mainly depend on the metabolites produced by biological material and their extracts, causing capping and stabilization for the particles and thus the formation of NPs. The superiority of biocompatible and environmentally friendly is fully utilized in a suitable approach for biological applications. The antibacterial mechanism of these NPs is mainly related to ROS and the destruction of the cell wall or membrane, although other processes such as electrostatic interaction and physical damage are also effective factors in applications of photocatalytic treatment. In general, this review of MgO NPs as biocompatible and eco-friendly material is a good guidance for biomedical applications. However, this paper is not suitable for publication in this form, which needs to be improved in light of the recommendations mentioned below.

Some major concerns are shown as following:

1. Bio-templates-mediated synthesis strategies: This part lack of summary and analysis for plant extracts, bacterial extracts, fungi extracts, and algae extracts. Obvious research results cannot convey the critical meaning for this review, and the distinction and commonality should be described in this section.

Response:

Thanks for mentioning the important points by the reviewer. The corrections have been applied to related sections in the manuscript.

2. Applications of photocatalytic treatment: The potential application of MgO NPs activity against microbial, biofilm, and fungal should be summarized attributed to the different mechanisms. According to the content, the views and comments of authors should be expressed.

Response:

Thanks for mentioning the important points by the reviewer. Antibacterial, antibiofilm, and antifungal activity mechanisms have been well explained in the text and views and comments of authors in each section have been expressed.

3. In this manuscript, the introduction should be restructured since it is considered too simple. Some related work should be reviewed in this part, for example: Catalysts, 2021, 11(7), 821; Advanced Fiber Materials, 2022, 4, 119; Industrial Crops and Products, 2022, 187, 115442; Composites Communications, 2022, 34, 101271. Additionally, the reason why the authors selected this point, the interaction of different performance and application should be added in the manuscript.

Response:

The structure of introduction has been changed and rewritten in a structured and coherent way. Also, new references and more information have been added to improve the introduction. The purpose of the study, the general review and the reason for conducting the study were written at the end of the introduction.

4. Page 11 Line 305: The “2.1. Algae extracts” should be amended to “2.4. Algae extracts”.

Response:

Thanks for the reviewer's attention. The related section number has been changed.

Reviewer 3 Report

Magnesium oxide nanoparticles (MgO NPs) have emerged as an promising antimicrobial platform owing to their unique physicochemical features, and they may be a potential option for overcoming the difficulties associated with the eradication of microbial biofilms and antibiotic resistance. This review examines current breakthroughs in biosynthetic techniques for MgO NPs from plant, bacterial, fungal, and algal extracts, as well as the processes, problems, and future possibilities of MgO NPs and associated nanocomposites for their effect on microbial, biofilm, and fungal strains. This reviewer considers this review has the potential to contribute to the green synthesis of MgO nanoparticles if the following concerns are addressed adequately:

1.    It is noted that your manuscript needs careful editing by someone with expertise in technical English editing paying particular attention to english grammar spelling, and sentence structure for lack of logic and coherence of the essay.

2.    There are some hazy photographs, such as Figure 5, and it is advised to select a more distinct alternative. And the serial numbers preceding the subheadings in the text are confusing; please review and re-calibrate.

3.    Figure 2 is extraneous to the presentation of the article's primary subject and does not fully explain what is shown. Instead, it is recommended that some figures be used to improve and summarize the methods and characteristics of Plant extracts. And the need for a clear diagram to cover the whole text is indispensable at the beginning of the article.

4.    In the applications of photocatalytic treatment section, it is proposed to mention more cutting-edge research on MgO nanoparticles and to highlight the challenges and goals of the present relevant research.

5.    In the conclusion part, it is necessary to provide a good overview and evaluation of the study development of magnesium oxide in order to communicate the author' opinions and contribute more of their ideas.

6.    The authors should cite more references in introduction for the wider readership. Such as Adv. Func. Mater. 2022, 32, 202200302；InfoMat, 2022, 4（7）, e12294.

Author Response

Reviewer 3:

Magnesium oxide nanoparticles (MgO NPs) have emerged as an promising antimicrobial platform owing to their unique physicochemical features, and they may be a potential option for overcoming the difficulties associated with the eradication of microbial biofilms and antibiotic resistance. This review examines current breakthroughs in biosynthetic techniques for MgO NPs from plant, bacterial, fungal, and algal extracts, as well as the processes, problems, and future possibilities of MgO NPs and associated nanocomposites for their effect on microbial, biofilm, and fungal strains. This reviewer considers this review has the potential to contribute to the green synthesis of MgO nanoparticles if the following concerns are addressed adequately:

1. It is noted that your manuscript needs careful editing by someone with expertise in technical English editing paying particular attention to english grammar spelling, and sentence structure for lack of logic and coherence of the essay.

Response:

Thank you for the hint. The entire text has been edited.

2. There are some hazy photographs, such as Figure 5, and it is advised to select a more distinct alternative. And the serial numbers preceding the subheadings in the text are confusing; please review and re-calibrate.

Response:

Thank you for your comment. All figures are edited, framed, and labeled.

3. Figure 2 is extraneous to the presentation of the article's primary subject and does not fully explain what is shown. Instead, it is recommended that some figures be used to improve and summarize the methods and characteristics of Plant extracts. And the need for a clear diagram to cover the whole text is indispensable at the beginning of the article.

Response:

It should be noted that plants contain many bioflavonoids, and these compounds have functional groups, such as hydroxyl. The formation mechanism begins with the ionization of magnesium nitrate, which produces Mg²⁺ and NO^3- ions in the solution. Following this, the hydroxyl group from the polyphenolic compounds forms a magnesium complex. Other phytochemicals, such as terpenoids, which are found in plants, also have the capacity to bind to the metal ion and, consequently, trigger (stabilize) the formation of Mg(OH). The removal of water molecules takes place via the calcination process, which results in the formation of metal oxide nanoparticles. Apart from this, figure 1 shows the schematic synthesis of biogenic MgO NPs by microorganisms and plants.

The reviewer is suggested to consider the following references:

https://doi.org/10.1016/j.sciaf.2022.e01366 / https://doi.org/10.1016/j.apt.2018.04.003

 

 

4. In the applications of photocatalytic treatment section, it is proposed to mention more cutting-edge research on MgO nanoparticles and to highlight the challenges and goals of the present relevant research.

Response:

Thanks for reviewer's comment. Several examples have added to manuscript to show various application of biogenic MgO NPs as well as antibacterial, antibiofilm, and antifungal activity mechanisms have been well explained in the text and views and comments of authors in each section have been expressed.

5. In the conclusion part, it is necessary to provide a good overview and evaluation of the study development of magnesium oxide in order to communicate the author' opinions and contribute more of their ideas.

Response:

Thanks for reviewer's comment. The conclusion part has been improved.

6. The authors should cite more references in introduction for the wider readership. Such as Adv. Func. Mater. 2022, 32, 202200302；InfoMat, 2022, 4（7）, e12294.

Response:

Suggested references have been added to the introduction section.

Reviewer 4 Report

The topic of the paper is quite interesting. The paper can be published after some corrections.

1.Authors claim that different factors influence the MgO NPs synthesis using plant extracts such as pH and temperature as well as the ratio and concentration of the precursors and extracts. However, Table 1 summarizes only green source and magnesium source. From the Table it is not clear in what way particle size and morphology were controlled. Were pH value and temperature varied to obtain MgO particles with different morphologies?

2.It is not clear why authors use terms “photocatalytic treatment, photocatalytic properties” etc.

For example:

 Applications of photocatalytic treatment (Part 3)

This part includes

3.1 Antimicrobial activity

3.2 Antibiofilm activity

3.3 Antifungal activity

Moreover, conclusions part includes the statement “MgO NPs as metal oxide NPs have special photocatalytic properties for antimicrobial, antifungal, and antibiofilm applications”.

The same thing with the article title “Green synthesis of magnesium oxide nanoparticles and nanocomposites for photocatalytic antimicrobial, antibiofilm, and antifungal applications”

It is not clear because photocatalytic activity of material is provided by its interaction with light.

No evidence of photocatalytic properties of MgO were described in the present review. There is a statement in the paper that Visible light photocatalysis is one of the possible mechanisms of antibacterial activity and refer to [143] reference. However, [143] reference describes a slight photocatalytic activity for inactivation of the bacteria (∼22% improvement in their antibacterial activity) for CuO nanoparticles but not MgO.

Authors also claim “The photocatalytic properties of MgO NPs play a significant role in removing environmental pollution and the antibacterial behavior of these nanoparticles” and refer to [41]. However, no details of the role of photocatalytic activity of MgO in antimicrobial, antibiofilm and antifungal properties were given.

3.The review is devoted to MgO NPs and nanocomposites synthesis and application. However, there is very little information on MgO-based nanocomposites. The role of nanocomposite formation in antimicrobial, antibiofilm and antifungal properties should be highlighted.

Authors should correct these essential things.

Author Response

Reviewer 4

The topic of the paper is quite interesting. The paper can be published after some corrections.

1.Authors claim that different factors influence the MgO NPs synthesis using plant extracts such as pH and temperature as well as the ratio and concentration of the precursors and extracts. However, Table 1 summarizes only green source and magnesium source. From the Table it is not clear in what way particle size and morphology were controlled. Were pH value and temperature varied to obtain MgO particles with different morphologies?

Response:

Thank you for this comment. Table 1 is related to the synthesis of nanoparticles using plant extracts. Due to the fact that the number of variables affecting the synthesis process is very large and this issue has not been mentioned in detail in various articles, other effective factors such as temperature and pH are briefly mentioned in this article. Examining all of the factors for various synthesis methods in the form of a new review article can be a novel and excellent idea.

2.It is not clear why authors use terms “photocatalytic treatment, photocatalytic properties” etc.

For example:

 Applications of photocatalytic treatment (Part 3)

This part includes

3.1 Antimicrobial activity

3.2 Antibiofilm activity

3.3 Antifungal activity

Moreover, conclusions part includes the statement “MgO NPs as metal oxide NPs have special photocatalytic properties for antimicrobial, antifungal, and antibiofilm applications”.

The same thing with the article title “Green synthesis of magnesium oxide nanoparticles and nanocomposites for photocatalytic antimicrobial, antibiofilm, and antifungal applications”

It is not clear because photocatalytic activity of material is provided by its interaction with light.

Response:

Photocatalytic activity in production of reactive oxygen species (ROS) has been described in the "Applications of photocatalytic treatment" section. The pro-oxidant activity of metallic and semiconductor nanoparticles typically originates from light-induced oxidative stress, caused by reactive oxygen species (ROS), examples of which include: superoxide anions (O₂^•−), hydroxyl radicals (^•OH), singlet oxygen ( O₂), dissolution of cations, internalization of nanostructures resulting in disintegration of the cell membrane, inhibition of enzyme activity and DNA synthesis, interruption of energy transduction, etc. Generally, ROS damages biomolecules, e.g. proteins, vitamins, and lipids (lipid peroxidation) of microbial cells, due to the strong oxidation potential of ROS. In addition to antibacterial activity, ROS also introduces anticancer and antitumor activity, leading to the use of these types of materials to have potential therapeutic applications.

No evidence of photocatalytic properties of MgO were described in the present review. There is a statement in the paper that Visible light photocatalysis is one of the possible mechanisms of antibacterial activity and refer to [143] reference. However, [143] reference describes a slight photocatalytic activity for inactivation of the bacteria (∼22% improvement in their antibacterial activity) for CuO nanoparticles but not MgO.

Response:

The evidence in photocatalytic activity and antimicrobial activity of biogenic MgO NPs have been provided in the "antimicrobial activity" section.

Authors also claim “The photocatalytic properties of MgO NPs play a significant role in removing environmental pollution and the antibacterial behavior of these nanoparticles” and refer to [41]. However, no details of the role of photocatalytic activity of MgO in antimicrobial, antibiofilm and antifungal properties were given.

Response:

Photocatalytic activity in production of reactive oxygen species (ROS) has been described in the "Applications of photocatalytic treatment" section. The pro-oxidant activity of metallic and semiconductor nanoparticles typically originates from light-induced oxidative stress, caused by reactive oxygen species (ROS), examples of which include: superoxide anions (O₂^•−), hydroxyl radicals (^•OH), singlet oxygen ( O₂), dissolution of cations, internalization of nanostructures resulting in disintegration of the cell membrane, inhibition of enzyme activity and DNA synthesis, interruption of energy transduction, etc. Generally, ROS damages biomolecules, e.g. proteins, vitamins, and lipids (lipid peroxidation) of microbial cells, due to the strong oxidation potential of ROS. In addition to antibacterial activity, ROS also introduces anticancer and antitumor activity, leading to the use of these types of materials to have potential therapeutic applications.

3.The review is devoted to MgO NPs and nanocomposites synthesis and application. However, there is very little information on MgO-based nanocomposites. The role of nanocomposite formation in antimicrobial, antibiofilm and antifungal properties should be highlighted.

Response:

To follow this opinion, various studies conducted on nanocomposites containing MgO and their properties, including antibacterial, were discussed and added to the review.

           

Authors should correct these essential things.

Round 2

Reviewer 2 Report

The authors have revised the manuscript carefully based on referees' comments. The scientific quality of this paper is greatly improved. The manuscript can be accepted at the present version. 

Reviewer 4 Report

The paper can be published in the present form.