Review History


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Summary

  • The initial submission of this article was received on March 29th, 2016 and was peer-reviewed by 3 reviewers and the Academic Editor.
  • The Academic Editor made their initial decision on May 31st, 2016.
  • The first revision was submitted on July 5th, 2016 and was reviewed by 2 reviewers and the Academic Editor.
  • A further revision was submitted on September 19th, 2016 and was reviewed by the Academic Editor.
  • The article was Accepted by the Academic Editor on September 20th, 2016.

Version 0.3 (accepted)

· · Academic Editor

Accept

Dear Prof. Patcharapon,

Congratulations!
Your paper is now ready to be published in PeerJ.

Best regards

Version 0.2

· · Academic Editor

Minor Revisions

Dear Authors,

Reviewer 3 has commented that your response to them that: "In the experiment, MIC is the lowest concentration of drug that inhibits the growth of the organism that it was observed the turbid or clear solution after the incubation time and also compared with broth alone control. Our results could provide the clear solution in the dose of MIC due to the killing bacteria aggregated with the nanoparticles underneath the broth solution. Furthermore, the sampling supernatants of each condition were measured with spectrophotometer" is not clear enough.

As you can see from their review, they would like you to respond more fully to this concern.

Reviewer 1 ·

Basic reporting

The manuscript deals with a trendy topic, because of the worldwide interest in silver nanoparticles (AgNPs) and in natural bioactive substances. Unfortunately the AgNPs production process exhibits a broad range of toxicity in vertebrates and invertebrates, and to avoid the chemical toxicity, biosynthesis (green synthesis) of metal nanoparticles is proposed as a cost-effective and environmental friendly alternative. Aloe vera leaf extract is an interesting natural medicinal agent with multiple properties, including an antibacterial effect.

Experimental design

The used methods are correct and effective and the obtained results demonstrate an
antibacterial activity on S. epidermidis and P. aeruginosa. The results showed that AgNPs had a high antibacterial effect, which depended on their synthesis conditions, particularly when processed at 100 oC for 6 h and 200 oC for 12 h. The cytotoxicity of AgNPs was determined using human PBMCs revealing no obvious cytotoxicity.

Validity of the findings

The work provides interesting and innovative findings, with applicative potential.

Comments for the author

The Authors have considered the given suggestions, mentioning at least the matter concerning the choice of testing only a limited number of microbial species.

·

Basic reporting

Authors provided point-by-point responses to each of the comments with some minor weakeness.

Experimental design

No comments

Validity of the findings

Please make clear again the way you provide evidence of the inhibitory (reversible) and microbicidal (irreversible) effects of nanoclusters against the two investigated strains
A recovery procedure and subsequent incubation test might provide evidence of reversibility/irreversibility of nanocluster aggregation observed at 0.01mg/mL and 0.0025mg/mL for S. epidermidis and P. aeruginosa strains. Otherwise, you will provide evidence by microscopy of cell membrane damage (pores) for the S. epidermidis at 0.01 mg/mL or for that of the P. aeruginosa one at 0.0025mg/mL.

Comments for the author

Please make the following minor changes.

At line 109 - please change “vera” with “vera”
At line 202 - please change “stain” with “strains”

Version 0.1 (original submission)

· · Academic Editor

Minor Revisions

Dear Patcharaporn,

Expert reviewers of the field have reviewed your paper and they have raised some criticisms on your work.

I invite you to carefully respond all the questions raised and resubmit the revised paper.

Best regards,
Maria Rosaria

Reviewer 1 ·

Basic reporting

The manuscript deals with a trendy topic, because of the worldwide interest in silver nanoparticles (AgNPs) and in natural bioactive substances. Unfortunately the AgNPs production process exhibits a broad range of toxicity in vertebrates and invertebrates, and to avoid the chemical toxicity, biosynthesis (green synthesis) of metal nanoparticles is proposed as a cost-effective and environmental friendly alternative. Aloe vera leaf extract is an interesting natural medicinal agent with multiple properties, including an antibacterial effect.

Experimental design

The used methods are correct and effective and the obtained results demonstrate an
antibacterial activity on S. epidermidis and P. aeruginosa. The results showed that AgNPs had a high antibacterial effect, which depended on their synthesis conditions, particularly when processed at 100 oC for 6 h and 200 oC for 12 h. The cytotoxicity of AgNPs was determined using human PBMCs revealing no obvious cytotoxicity.

Validity of the findings

the work provides interesting and innovative findings, with applicative potential.

Comments for the author

In general I think that a larger number of microbial species should has to be tested, so I think the Authors have to explain why they tested only two microbial strains and why they tested those two strains. The Authors have to consider and underline this aspect when they discuss the obtained results.

Reviewer 2 ·

Basic reporting

No Comments

Experimental design

No Comments

Validity of the findings

No Comments

Comments for the author

Patcharaporn Tippayawat et al. report Green synthesis of silver nanoparticles in aloe veraplant extract prepared by a hydrothermal method and their synergistic antibacterial activity. The results are impressive especially for the antibacterial activity section. The article is suitable for this journal according to the content aspect. I recommend this article for publication.
Nevertheless, I have some suggestions which are listed below.
1. It is better to provide some representative TEM images of the obtained Ag nanoparticles because the AgNP in the SEM images in this study were aggregated from which the diameter measurement seems difficult.
2. If it is possible please provide the UV absorption spetra of the obtain colloid because the surface plasmon resonance band (PRB) of the Ag colloid can indicate some structural information.

·

Basic reporting

In the following some criticisms and weakeness are summarized.

Some works from literature have been carried out focused on green biosynthesis of silver nanoclusters with antimicrobial functionalities, some of them are also cited into the manuscript. Authors must indicate with clarity what the gap of knowledge their results have been covering beyond he state of the art.

Dose-relationships between the concentration of the silver nanoclusters (as obtained at 100°C and 6h as well as at 200°C and 12h) and load of vital microbial cell are strongly recommended to be reported and discussed in depth in the manuscript.

For a more easy reading, the manuscript should report the state of the art in the introduction section only.

Experimental design

Authors should report more information about the experimental method used to estimate MIC levels as well as on how they accounted for the medium turbidity due to the presence of the silver nanoclusters during the growth/inhibition tests.

Validity of the findings

A storage stability study about the antimicrobial ability for the two types of the more effective silver nanoclusters is lacking. No data are provided about nano structures and residual antimicrobial ability during storage intended for biotechnological or medical applications

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