Surface Plasmon Resonance Sensor Based on Polypyrrole–Chitosan–BaFe2O4 Nanocomposite Layer to Detect the Sugar
, Mahmoud Naseri 3, Ahmad Mohammadi 4, Yap Wing Fen 5,*, Suhidi Shafie 1 and Halimah Mohamed Kamari 5Round 1
Reviewer 1 Report
This manuscript by Sadrolhosseini et al. describes a method of using electrochemically deposited composite film of PPy-chitosan-BeFe2O4 for low concentration sugar sensing. Overall it can be considered for publication in Applied Sciences. There are, however, some points that need the authors' attention.
Is chitosan soluble in pH 7.2 PBS? The authors may also want to specify what type of chitosan used in this experiment. The authors use the unit ppm to describe sugar concentrations. Although understandable for such low concentrations, it is not easy to directly compare them with other results. Normally, the units for the blood sugar level are mmol/l or mg/dL The significant figures of the FTIR peak positions, thickness of the films, and SPR angles all imply extremely high resolution of the instruments. For example, 7.3 nm of thickness suggests sub-nanometer resolution from the profilometer. The authors may want to double-check that. The equation (1) in the text is not properly shown. How many samples are used for each measurement? There are other typos. For example, Line 73: “Ca (NO3)2.H2”.
Author Response
Dear Reviewer
The authors appreciate you for your constrictive comments and the manuscript was improved as follows:
Comments and answers
This manuscript by Sadrolhosseini et al. describes a method of using electrochemically deposited composite film of PPy-chitosan-BeFe2O4 for low concentration sugar sensing. Overall it can be considered for publication in Applied Sciences. There are, however, some points that need the authors' attention.
1-Is chitosan soluble in pH 7.2 PBS?
Answer
The chitosan was prepared before to it use for electrodeposition. The manuscript was improved as follows:
To prepare the electrolyte solution for electrodeposition of PPy-Chi-BaFe2O4, 0.2 g chitosan powder was dissolved in 50 ml aqueous solution of 0.3M oxalic acid and it was stirred 4h prior to its use for preparation of layer.
2-The authors may also want to specify what type of chitosan used in this experiment.
Answer
The chitosan was purchased from Sigma Aldrich company in medium molecular weight. The materials part was improved as follows:
……..chitosan (Medium Molecular Weight, (75%-85 deacetylated))………
3-The authors use the unit ppm to describe sugar concentrations. Although understandable for such low concentrations, it is not easy to directly compare them with other results. Normally, the units for the blood sugar level are mmol/l or mg/dL.
Answer
The text was improved and the unit of mg/dL was added.
4-The significant figures of the FTIR peak positions, thickness of the films, and SPR angles all imply extremely high resolution of the instruments. For example, 7.3 nm of thickness suggests sub-nanometer resolution from the profilometer. The authors may want to double-check that.
Answer
The FT-IR peak positions were checked and corrected the text. The Table 1 was added to present results.
The minimum resolution of profilometer was 1nm. We measured the thickness of layers with the profilometer. After that, the layers were attached to prism and the SPR signals were registered in the presence of DDW. The SPR signal were analyzed using minimum root square as an equation 2 and the refractive index and the high accuracy thickness (0.1 nm) have been found. It was necessary that the range of thickness of layers was cleared before the analysis of SPR signals. To clarify the manuscript, the text was improved and the results were listed in Table 1.
5-The equation (1) in the text is not properly shown.
Answer
The equation (2) [(1) is old Number] was rewrite and corrected.
6-How many samples are used for each measurement?
Answer
Three sugars (glucose, fructose and sucrose)
Six concentration of each sample were used to test using SPR sensor (0.005, 0.05, 0.5, 5 10 25 ppm)
The experiment was repeated 10 times for each concentration of sugar.
The preparation of sugar solution section was improved as follows:
In this research, glucose, fructose, and sucrose (three sugar) in six concentration were used to do experiment and the SPR experiment was repeated 10 times for each concentration of sugar.
7-There are other typos. For example, Line 73: “Ca (NO3)2.H2”.
Answer
The manuscript was checked and the corrected of error typos.
The authors improved the manuscript based on your comments and they hope this article will be published in Applied sciences. If you have any question, comments or suggestion, would you please don’t hesitate to ask them.
Yours Sincerely
Dr. Amir Reza Sadrolhosseini
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript reports electrodeposition of a polypyrrole-chitosan-BaFe2O4 nanocomposite on a gold film for sugar detecting. This work can be considered for publication after addressing the following comments:
- In the title, it is not correct to write a composition like this: “Polypyrrole Chitosan Barium Ferrite Nanocomposite”.
- It is unclear what is the aim of the work when reading the abstract. The authors report the use of surface plasmon resonance for sensing, what is a relation of the “polypyrrole-chitosan-BaFe2O4 nanocomposite” to the sensing property and the surface plasmon resonance, it should be discussed in the introduction section.
- Which ions are referred to in this phrase: “The experiment was repeated separately for each ion about 10 times.”?
- There are many unassigned peaks in the XRD pattern with the intensity of the same order of the assigned peaks. I don’t think the XRD pattern has been assigned correctly.
- The discussion from Line 141 to 163 is very vague, it must be completely rewritten. Please also explain how BaFe2O4 can form in the film during the electrodeposition process in the discussion section.
- Please provide thickness in Figure 3b.
- Please discuss why “the degree of absorption for the glucose is higher than the degree of adsorption of fructose and sucrose”?
Author Response
Dear Reviewer
The authors appreciate you for your constrictive comments and the manuscript was improved as follows:
Comments and answers
This manuscript reports electrodeposition of a polypyrrole-chitosan-BaFe2O4 nanocomposite on a gold film for sugar detecting. This work can be considered for publication after addressing the following comments:
1- In the title, it is not correct to write a composition like this: “Polypyrrole Chitosan Barium Ferrite Nanocomposite”.
Answer
The title was corrected as demanded. (Polypyrrole-Chitosan-BaFe2O4)
2- It is unclear what is the aim of the work when reading the abstract. The authors report the use of surface plasmon resonance for sensing, what is a relation of the “polypyrrole-chitosan-BaFe2O4 nanocomposite” to the sensing property and the surface plasmon resonance, it should be discussed in the introduction section.
Answer
The Polypyrrole-chitosan-BaFe2O4 layer was used to improve the gold. The abstract, and introduction were improved as follows:
Abstract: The surface plasmon resonance sensor was used to detect and measure the low concentration of sugar. A polypyrrole-chitosan-BaFe2O4 nanocomposite layer was prepared to improve the surface of the gold layer for detection of glucose, fructose, and sucrose using surface plasmon resonance technique.
In introduction
Moreover, the surface plasmon resonance (SPR) sensor is a versatile and accurate method to detect the chemical materials and sugar. The SPR phenomena occurs at the interface of two medium with opposite dielectric sign. Normally, the gold layer is used for the SPR sensors and the sensing layer has been coated on the surface of gold layer to improve the sensitivity and selectivity of the sensor. Recently, the nanocomposite layers have been used for sensing layer. The gold nanoparticle, carbon-based nanostructure [1], and magnetic nanoparticles were used to improve the sensitivity of the sugar sensor. Magnetic nanoparticles have some advantage such as high catalytic efficiency, good stability and mono-dispersion [2]. Hence, many researchers used the magnetic nanoparticles such as ZnFe2O4 [2], Fe3O4 [21], and polypyrrole-chitosan/Fe2O3 nanocomposite [16] to detect the glucose and others sugar and the detection limit was in the range of 1 to 3 µM and the ratio of signal to noise was about 3. Consequently, the magnetic nanoparticles are considerable nanostructure to design the sugar sensor.
3- Which ions are referred to in this phrase: “The experiment was repeated separately for each ion about 10 times.”?
Answer
The measurement of low concentration of sugars is the subject of this study. So, the manuscript was corrected as follows:
The experiment was repeated separately for each sugars about 10 times. The SPR signal was analyzed using the Fresnel theory based on the matrix method for a multi-layer system [26].
4- There are many unassigned peaks in the XRD pattern with the intensity of the same order of the assigned peaks. I don’t think the XRD pattern has been assigned correctly.
Answer
In Figure 2(b), the important XRD peaks for evaluation of BaFe2O4 is in the range of 20° to 50°. So to clarify the results, the peaks at 39.5° and 59.7° were assigned that related to reflection plane of (420) and (120). The peak at 21.4° correspond to PPy-Chi. The XRD result was improved.
5- The discussion from Line 141 to 163 is very vague, it must be completely rewritten. Please also explain how BaFe2O4 can form in the film during the electrodeposition process in the discussion section.
Answer
The discussion from line 152 to 169 (141 to 163) was corrected and rewrote as follows:
Figure 2(c) shows the FE-SEM image of PPy-Chi-BaFe2O4 nanocomposite layer. The PPy-Chi-BaFe2O4 composite layer was formed during electro-polymerization of pyrrole in the presence of chitosan, LiClO4 (as a dopant) and BaFe2O4 nanoparticles and the chitosan agglomerated the polypyrrole and BaFe2O4 nanoparticles during the electro-polymerization of pyrrole. Finally, the PPy-Chi-BaFe2O4 composite layer was formed on the surface of gold layer [16]. BaFe2O4-NPs was scattered on the surface of layer and it impressed the morphology of the PPy-Chi-BaFe2O4 nanocomposite layer [31].
The essential charges for organizing the PPy were electrons and anions that LiClO4 and BaFe2O4 provided them. Therefore, the role of LiClO4 and BaFe2O4 were as the electron and anions charges to create the counterbalance of PPy-Chi-BaFe2O4 composite layer. Hence, the polymer electropolymerized at the surface of the working electrode, containing BaFe2O4 nanoparticles [32].
The mechanism was added to text as follows:
During the electrodeposition process, monomer molecules and metal ions at the electrode-electrolyte interface deposited on the surface of the working electrode by reaching the proper applied potential and the mechanism is as follows:
(1)
6- Please provide thickness in Figure 3b.
Answer
The Figure 3(b) and 3(c) were corrected and the thickness of layer was added to figure. The Table 1 was added to manuscript to list the optical parameters.
7- Please discuss why “the degree of absorption for the glucose is higher than the degree of adsorption of fructose and sucrose”?
Iron oxide nanoparticles and chitosan can be used for sugar sensor application because they have contribution to transfer electron between receptor and sugar [16]. The molecule of glucose has higher tendency than other sugar to make the bond and contribute to exchange the electron with chitosan and BaFe2O4. Figure 7 shows the binding model of glucose and PPy-Chi-BaFe2O4. The molecules of sucrose is very heavy and the tendency to make a bond with other elements is very weak.
Figure 7. Molecular modeling of interaction between glucose and PPy-Chi-BaFe2O4
The authors improved the manuscript based on your comments and they hope this article will be published in Applied sciences. If you have any question, comments or suggestion, would you please don’t hesitate to ask them.
Yours Sincerely
Dr. Amir Reza Sadrolhosseini
Round 2
Reviewer 2 Report
The discussion on why “the degree of absorption for the glucose is higher than the degree of adsorption of fructose and sucrose”? is unclear. In fact, a new added text does not provide any information. Figure 7 must be removed because it does not show any relevant information about the comment. This discussion must be improved significantly.
Author Response
Dear Reviewer
The authors appreciate you for your constrictive comment and the discussion section was improved as follows:
The discussion on why “the degree of absorption for the glucose is higher than the degree of adsorption of fructose and sucrose”? is unclear. In fact, a new added text does not provide any information. Figure 7 must be removed because it does not show any relevant information about the comment. This discussion must be improved significantly.
Answer
The discussion for the degree of adsorption of glucose by PPy-Chi-BaFe2O4 was improved as follows:
Magnetic nanoparticles and chitosan can be used for sugar sensor application because they contribute to transfer the electron between a receptor (sensing layer) and sugar [16, 38, 39]. The BaFe2O4- NPs can enhance the electron transfer between glucose, fructose and sucrose with sensing layer. The molecule of glucose contains more hydroxyl group (OH) and one hydroxymethyl group (CH2OH) at the edge of molecule plane and the hydroxyl group can interact with BaFe2O4-NPs in the sensing layer. The difference between glucose and fructose is in the number of hydroxyl group at the edge of molecule planes so that fructose contains two hydroxymethl groups (CH2OH) at the edge of molecule plane and they cause the space moment between fructose and BaFe2O4-NPs. Moreover, the number of hydroxyl group (OH) in glucose is higher than fructose. Therefore, the tendency of glucose to exchange the electron with sensing layer is higher than fructose [39, 40]. The molecule of sucrose is combination of glucose and fructose and it is very heavy and stable. Hence, the tendency of sucrose to exchange the electron with BaFe2O4-NPs is very weak. Consequently, the degree of adsorption for the glucose is higher than the degree of adsorption of fructose and sucrose. Therefore, the PPy-Chi-BaFe2O4 nanocomposite layer is sensitive to bind the low concentration of the glucose.
The Figure 7 was removed as demanded.
The authors improved the manuscript based on your comment and they hope this article will be published in Applied sciences. If you have any question, comments or suggestion, would you please don’t hesitate to ask them.
Yours Sincerely
Dr. Amir Reza Sadrolhosseini
Author Response File: Author Response.pdf
