Bacterial Detection and Differentiation of Staphylococcus aureus and Escherichia coli Utilizing Long-Period Fiber Gratings Functionalized with Nanoporous Coated Structures

Round 1

Reviewer 1 Report

Manuscript

Bacterial Detection and Differentiation of Staphylococcus aureus and Escherichia coli Using Long-Period Fiber Gratings Functionalized by Nanoporous Coated Structures

 

Shuyue He, Jue Wang, Fan Yang, Tzu-Lan Chang, Ziyu Tang, Kai Liu, Shuli Liu,Fei Tian, Jun-Feng, Liang, Henry Du and Yi Liu

This research is a very innovative and encompasses many goals associated with synthetic biology, microbiology and development of biosensors for biotechnology and biomedical engineering. A long-period fiber gratings (LPFG)-based biosensor with nanoporous coated structures for rapid bacterial detection of Staphylococcus aureus was developed. The specific adhesion and interaction of S. aureus on LPFG surfaces with nanoporous structure coatings induced immediate resonance wavelength (RW) shift in the transmission spectrum of the LPFG. The bacterial differentiation and S. aureus specificity of the method was confirmed through a series of studies using E. coli. The nanoporous structure enabled LPFG-based biosensor scheme developed holds a significant promise for rapid, reliable, and low-cost detection of S. aureus for biomedical and biotechnological applications.

Some comments to the authors:

1)     It should be written in italic in the title Staphylococcus aureus, Escherichia coli.

2)     It should be written in italic, Staphylococcus aureus, S. aureus in the paragraphs 19, 20, 24, 27, 28.

3)     It should be written in „italic“ E.coli in the paragraphs 25, 29.

4)     I didnʼt find the „Materials and Methods“ part in the manuscript.

 

 

 

Comments for author File: Comments.pdf

Author Response

Reviewer 1

Comments and Suggestions for the Authors

This research is a very innovative and encompasses many goals associated with synthetic biology, microbiology and development of biosensors for biotechnology and biomedical engineering. A long- period fiber gratings (LPFG)-based biosensor with nanoporous coated structures for rapid bacterial detection of Staphylococcus aureus was developed. The specific adhesion and interaction of S. aureus on LPFG surfaces with nanoporous structure coatings induced immediate resonance wavelength (RW) shift in the transmission spectrum of the LPFG. The bacterial differentiation and S. aureus specificity of the method was confirmed through a series of studies using E. coli. The nanoporous structure enabled LPFG-based biosensor scheme developed holds a significant promise for rapid, reliable, and low-cost detection of S. aureus for biomedical and biotechnological applications.

Some comments to the authors:

We thank the reviewer for the encouraging comments and recognition of the prospect on our work.

1. It should be written in italic in the title Staphylococcus aureus, Escherichia coli.

Thanks for the comments. We have updated it.

2. It should be written in italic, Staphylococcus aureus, S. aureus in the paragraphs 19, 20, 24, 27, 28.

It has been updated in the text.

3. It should be written in „italic “E.coli in the paragraphs 25, 29.

We have fixed this issue in the manuscript.

4. I didnʼt find the „Materials and Methods “part in this manuscript.

Thanks for pointing it out. Initially, we provided the Experimental Section into the Supplementary. We have moved the Experimental Section to the main text in the updated version of the manuscript.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper investigates the protection against bacteria using surfaces with nanoporous structures.. It is expected to contribute to the development of the field. It would be worthy of publication if the following points were corrected.

Although the technique reported by the authors can be produced using a simple method and is expected to be a novel method of protection against bacteria, the manuscript raises the following questions.

What does 'RW' stand for in line 71 in the Introduction part?

The authors have applied 10 layers of PAH and PAA, what are the reasons for this multilayer structure, and how does it differ compared to a PAH/PAA monolayer structure?

The SEM images are shown in Fig. 2a, what is the mechanism by which these pores are generated? In addition, Fig. 2b shows that pores with diameters in the range 300-350 nm are the most common, but can the size of these holes be controlled by changing the preparation conditions?

Can the method reported by the authors in the present study be used to selectively detect target bacteria in conditions where other (harmless) bacteria are present?

It is well written. I consider it worthy of acceptance if the sections I commented on to the author can be corrected.

Author Response

Reviewer 2

Comments and Suggestions for the Authors

This paper investigates the protection against bacteria using surfaces with nanoporous structures. It is expected to contribute to the development of the field. It would be worthy of publication if the following points were corrected.

Although the technique reported by the authors can be produced using a simple method and is expected to be a novel method of protection against bacteria, the manuscript raises the following questions.

1. What does 'RW' stand for in line 71 in the Introduction part?

We thank reviewer for the comments.

As shown in Abstract, the “RW” means “resonance wavelength”. To make it clear, we have added the full name of RW in line 71.

2. The authors have applied 10 layers of PAH and PAA, what are the reasons for this multilayer structure, and how does it differ compared to a PAH/PAA monolayer structure?

This is a good question. The monolayer of PAH/PAA coating is too thin to generate nanoporous structures. Recently, we found that there is a range limitation of the size of nanoporous structures based on the different layers of PAH/PAA coatings. For example, the size range of 10 layered coatings is ~300nm to ~800nm, and the size range of 20 layers of the coatings is ~800nm to ~2um. We are drafting our next manuscript to discuss the details of the results.

3. The SEM images are shown in Fig. 2a, what is the mechanism by which these pores are generated? In addition, Fig. 2b shows that pores with diameters in the range 300-350 nm are the most common, but can the size of these holes be controlled by changing the preparation conditions?

The scheme of the mechanism of pH-induced nanoporous structure in PAH/PAA coatings is shown in Fig. 1. Generally, the COO^- groups of PAA readily bind to the NH₃⁺ groups of PAH, forming –NHCO– ionic intermolecular cross-links. In the low-pH environment, the hydrogen cations protonate some of the COO^- groups, leading to breakage of interchain ion-pairs of LbL and thus increased mobility of polymer chains. It allows more energetically favorable reorganizations of the chains on the surface. This reorganization results in an insoluble swelling polyelectrolyte complex, which is followed by phase separation in the neutral solution via a spinodal decomposition process and thus forming nanopores.

As mentioned in comment 2, we are working on the study of different sized nanoporous structures. We have successfully controlled the size of nanopores at ~300nm, ~800nm, ~1.2um, ~1.6um and ~2um by changing the experimental temperatures, the reaction times, and the different pH. We will provide more details in our next manuscript.

4. Can the method reported by the authors in the present study be used to selectively detect target bacteria in conditions where other (harmless) bacteria are present?
5. aureusand E. coliare the most prevalent gram positive/negative bacteria that has been studied. In hospital settings, S. aureus and E. coli are the primary source of nosocomial infections; it is crucial and meaningful to detect and investigate in these two bacteria in order to reduce their impact on human and animal health. Since bacterial detection is very complicated, we need to study it step by step. This study provides an insight that our designed coatings could work for the detection and differentiation of S. aureus and E. coli, this technology could potentially serve as a foundation and enable fiber sensing arrays which is able to selectively detect target bacteria in the future (Ref: MJ Aernecke, et al. Sensors and Actuators B: Chemical, 2009). This platform has great potential for the high sensitivity, rapid detection and data transfer, as well as networking. We are also excited and interested in the target bacterial detection by such label-free biosensors. We will devote to the detection of multi-cultures on the platforms we designed in our next step.

It is well written. I consider it worthy of acceptance if the sections I commented on to the author can be corrected.

We thank the reviewer for the encouragement and all comments again!

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper aim is to present  a method for rapid bacterial detection of a dangerous cause of nosocomial infection with the S. aureus,  and this is  a topical one nowadays.  The coatings proposed for  detection use long-period fiber gratings (LPFG) integrated  with functional polyelectrolyte with designed nanoporous structures.  As other merits paper has a properly selected title  and a suitable concise abstract presenting the paper content. sle and an informative abstract. There are  as well weaknesses to be corrected  before publication, taking into account the following 

 1 the original character needs to be presented clearly based on existing literature, 

2 to introduced  a subchapter about Experimental part with presentation with details of  materials and methods. In the present form of manuscript absence of nanoporous [PAH/PAA]10-PAH coatings elaboration and its mechanism are indicated references 37 and 38 from ten years ago,

3 to take into account a better organization of all data. The information about materials and methods being  in a paragraph with results and discussion, but with no details. 

Author Response

Reviewer 3

Comments and Suggestions for the Authors

The paper aim is to present a method for rapid bacterial detection of a dangerous cause of nosocomial infection with the S. aureus, and this is a topical one nowadays.  The coatings proposed for detection use long-period fiber gratings (LPFG) integrated with functional polyelectrolyte with designed nanoporous structures.  As other merits paper has a properly selected title and a suitable concise abstract presenting the paper content. sle and an informative abstract. There are as well weaknesses to be corrected before publication, taking into account the following. 

1. the original character needs to be presented clearly based on existing literature, 

Thanks very much for the comments.

We have added the original character, such as resonance wavelength (RW), in line 71.

2. to introduced a subchapter about Experimental part with presentation with details of materials and methods. In the present form of manuscript absence of nanoporous [PAH/PAA]10-PAH coatings elaboration and its mechanism are indicated references 37 and 38 from ten years ago,

Initially, we provided the Experimental Section into the Supplementary. We have moved the Experimental Section to the main text in the updated version of the manuscript.

3. to take into account a better organization of all data. The information about materials and methods being in a paragraph with results and discussion, but with no details. 

To make the structure of the manuscript clearer, we have provided the materials/chemicals and the preparation methods separately in the Experimental Section in text.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

I do consider that the paper despite  some improvements  in order to be published   need another revision. 

The original character has to be presented based on other existing papers and not in a  sentence in line 71 

Author Response

We appreciate the reviewer’s comments and explanation. Compared to the existing papers, this study aims to provide a new platform with small sized porous structures to detect different bacteria. We made an effort on the preparation of the platform since it is a challenge to fabricate the small sized porous structures, therefore, the scheme of the mechanism of the porous structure fabrication has been depicted in the text. In order to investigate the properties of the nanoporous structures on the bacterial adhesion, we have fabricated the different sized nanoporous structures already and we are investigating the size effect of the porous structures on bacterial detection; the exciting results will be included in our coming manuscripts. This manuscript provided a good fundamental and exciting results for the bacterial detection on the small sized nanoporous structures. In this manuscript, we also investigated the ability of differentiation of the Layer-by-Layer (LbL) coatings on two bacteria. This is newfound that the LbL coating were much able to differentiate S. aureus and E. coli perhaps due to the limited ability of E. coli adhesion on LbL coatings. Thus, we provided a platform to facilitate the bacterial detection and fabricate a biosensor with a potential to be used for future studies in multi-cultures. Therefore, our study is reliable and meaningful, and it deserves to be published.

Author Response File: Author Response.pdf