Enhancement in the antibacterial activity of cephalexin by its delivery through star-shaped poly(ε-caprolactone)-block-poly(ethylene oxide) coated silver nanoparticles

The antibacterial activity of silver nanoparticles (AgNPs) stabilized with a four-armed star-shaped poly(ε-caprolactone)-block-poly(ethylene oxide) copolymer [St-P(CL-b-EO)] and its application as a drug delivery vehicle for cephalexin (Cp) was evaluated against pathogenic Staphylococcus aureus. The prepared AgNPs were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, zeta sizer and atomic force microscopy (AFM). The antibacterial efficiency of Cp is enhanced several-fold by its delivery through complexation with St-P(CL-b-EO)-AgNPs, monitored by microplate assay and biofilm destruction studies. Finally, the visual destruction of bacterial cells and its biofilms by employing Cp and its conjugates at their minimum inhibitory concentration (MIC50) and minimum biofilm inhibitory concentration (MBIC50), respectively, is observed by topographic imaging by AFM. Enhanced antibacterial activity of St-P(CL-b-EO)-AgNPs loaded Cp is attributed to penetrative nature of the drug cargo St-P(CL-b-EO)-AgNPs towards the bacterial cell wall.

(2) The authors should discuss why they choose the block ratio with star-PCL10K and  The morphology of nanoparticles should also be characterized by TEM. (4) The loading efficiency of drug should be determined.
The stability of material should also be studied by DLS test to monitor the size change.
Decision letter (RSOS-201097.R0) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Dr Malik: Title: Enhancement in the Antibacterial Activity of Cephalexin by its Delivery through Starshaped Poly(ε-caprolactone)-block-poly(ethylene oxide)-AgNPs Manuscript ID: RSOS-201097 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
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How about the materials' stability? This point is very critical if we consider practical applications.
The authors show wide-angle XRD patterns for samples. How about the average crystallite sizes? This size is matched with TEM data?
Related papers have been reported by different research groups. It is better to cite the following refs to support some related paragraphs in the introduction part.
Overall the manuscript is well written, but I want to see the authors' perspective (future vision) on this research in the conclusion part.
Reviewer: 2 Comments to the Author(s) Silver nanoparticles (AgNPs) were prepared by stabilization with 4-arm star-shaped block copolymer [St-P(CL-b-EO)] and its application as drug delivery vehicle for cephalexin (Cp) was evaluated against pathogenic Staphylococcus aureus. The manuscript can be accepted for publication after issuing the following considerations.
(1) The characterization data of St-P(CL-b-EO) sample used in this work should be provided in the supporting information.
(2) The authors should discuss why they choose the block ratio with star-PCL10K and MeO-PEO2K?
(3) The morphology of nanoparticles should also be characterized by TEM.
(4) The loading efficiency of drug should be determined.
(5) The stability of material should also be studied by DLS test to monitor the size change.
Author's Response to Decision Letter for (RSOS-201097.R0) See Appendix A.

Are the interpretations and conclusions justified by the results? Yes
Is the language acceptable? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? Yes

Recommendation? Accept as is
Comments to the Author(s) Improved.

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Are the interpretations and conclusions justified by the results? Yes
Is the language acceptable? Yes

Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
The authors have successfully addressed most of the concerns raised by the reviewers, thereby I think it can be considered for publication. Before that, I still hold the opinion that the authors should put all th DETAILED characterization data of polymers in the ESI, including SEC, 1H NMR, etc.

Decision letter (RSOS-201097.R1)
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Dear Dr Malik: Title: Enhancement in the Antibacterial Activity of Cephalexin by its Delivery through Starshaped Poly(ε-caprolactone)-block-poly(ethylene oxide)-AgNPs Manuscript ID: RSOS-201097.R1 Thank you for submitting the above manuscript to Royal Society Open Science. On behalf of the Editors and the Royal Society of Chemistry, I am pleased to inform you that your manuscript will be accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the reviewers' comments at the end of this email.
The reviewers and handling editors have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your manuscript.
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Reviewer: 2 Comments to the Author(s) The authors have successfully addressed most of the concerns raised by the reviewers, thereby I think it can be considered for publication. Before that, I still hold the opinion that the authors should put all th DETAILED characterization data of polymers in the ESI, including SEC, 1H NMR, etc.

Decision letter (RSOS-201097.R2)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.

Dear Dr Malik:
Title: Enhancement in the Antibacterial Activity of Cephalexin by its Delivery through Starshaped Poly(ε-caprolactone)-block-poly(ethylene oxide)-AgNPs Manuscript ID: RSOS-201097.R2 It is a pleasure to accept your manuscript in its current form for publication in Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
The comments of the reviewer(s) who reviewed your manuscript are included at the end of this email.  (2) The authors should discuss why they choose the block ratio with star-PCL10K and

MeO-PEO2K?
We selected the block ratio of star-PCL10K and MeO-PEO2K just to keep the ratio of same content of hydrophobic and hydrophilic segments. In further studies, we plan to compare the selectivity of the block lengths, their ratios of star block copolymer in context of their efficiency as antibacterial material.
(3) The morphology of nanoparticles should also be characterized by TEM.
In this study morphology and size of the NPs is studied through AFM. As a complementary technique we employed zetasizee (DLS) and zetapotential to confirm the size, size distribution, and stability of NPs before and after encapsulation with drug. The relevant discussion in the manuscript is given below The (4) The loading efficiency of drug should be determined.
Loading efficiency of the synthesized NPs is now added in the manuscript. The additions in the manuscript in this connection are . Experimental Section:

Determination of Loading Efficiency
Loading efficincy of drug in the above-mentioned compelxation is determined through UV visible spectrophotometer (Shimadzu, UV-240, Hitachi U-3200). In brief, above-mentioned formulation of drug and nanoparticles was centrifuged at 14000 rpm for 25 min. The pellets at the bottom of the Eppendorf tube were carefully collected, followed by dissolution of these pellets in acetone. In results indicate that we can achieve higher drug loading by using star shaped polymer.
(5) The stability of material should also be studied by DLS test to monitor the size change.
This is already discussed in the manuscript as

Response to the Reviewer's Comments (RSOS-201097R1)
Reviewer: 2 Comments to the Author(s) The authors have successfully addressed most of the concerns raised by the reviewers, thereby I think it can be considered for publication. Before that, I still hold the opinion that the authors should put all th DETAILED characterization data of polymers in the ESI, including SEC, 1H NMR, etc.