Advances in Electrochemical Aptasensors Based on Carbon Nanomaterials
Round 1
Reviewer 1 Report
In this review, the authors introduced not only the aptasensors, but also the fabrications and properties of a series of carbon based nanomaterials, such as CNT, graphene, carbon black etc. The advantages of each carbon materials in aptasensor have been briefly introduced. The table summarized the most recent works using CNT and graphene for Aptasensors. The review includes most important references and works; the reviewer suggests accept after the authors make following revision.
This reviewer suggests adding “sensor” as one of the keyworks.
There are some typo in line 90, 165, 376….
The authors have nicely introduced from sensor to biosensor and then to aptasensor in the Introduction, while only a small paragraph was used to introduce the role of carbon materials in aptasenors. It is better that the authors can give more information of why carbon materials are important in aptasenor and how they can help to improve the performance of aptasensors.
The authors mentioned the preparations of graphene by mechanical exfoliation and CVD. Are there any examples using those two types of graphene for aptasensors? If so, please add in the review.
In Line 180, the references about using Graphene as carriers for Au and redox molecules should be given.
The table summarized the most recent works using CNT and Graphene for aptasensors. It would be better that the authors could give more details about how the carbon materials was integrated with the aptamers. The typical scheme or Figures from the reported works should be added in this review.
The performance (for example, detection limits) of carbon nanomaterials based aptasensors listed in the table should be compared, or discussed in the Review.
Author Response
We are grateful to the reviewers for very useful comments that allowed us to improve manuscript.
In this review, the authors introduced not only the aptasensors, but also the fabrications and properties of a series of carbon based nanomaterials, such as CNT, graphene, carbon black etc. The advantages of each carbon materials in aptasensor have been briefly introduced. The table summarized the most recent works using CNT and graphene for aptasensors. The review includes most important references and works; the reviewer suggests accept after the authors make following revision.
Comment: This reviewer suggests adding “sensor” as one of the keywords.
Response: ‘Sensor’ was added in the keywords as requested
Comment: There are some typo in line 90, 165, 376….
Response: We have corrected typos mentioned
Comment: The authors have nicely introduced from sensor to biosensor and then to aptasensor in the Introduction, while only a small paragraph was used to introduce the role of carbon materials in aptasenors. It is better that the authors can give more information of why carbon materials are important in aptasenor and how they can help to improve the performance of aptasensors.
Response: We agree with this comment and the following paragraph was added in the Introduction (Ln 96-107):
"However, carbonaceous nanomaterials show many other advantages that make them very attractive in the assembly of electrochemical aptasensors. Most of them exert electroconductivity sufficient for electric wiring of redox active species involved in target interactions. This is particularly important for aptamers that do not exert any redox activity and need specific labels or redox indicators for signal generation. Then, many of carbon nanomaterials contain surface groups that might be involved in the immobilization of aptamers (hydroxyl and carboxylate groups). Moreover, such groups are obtained spontaneously in mechanical treatment of appropriate materials. But their quantities can be increased by additional chemical or electrochemical oxidation. Then, carbon nanomaterials increase the specific surface of the electrode and hence density of biorecognition elements to be immobilized. Finally, carbon nanomaterials can be easily modified by chemical treatment so that their properties including charge, shape and size can be directly varied in a broad range."
Comment: The authors mentioned the preparations of graphene by mechanical exfoliation and CVD. Are there any examples using those two types of graphene for aptasensors? If so, please add in the review.
Response: Unfortunately, we have not found examples of the application of several types of graphene in a single aptasensor. The following sentence was added (Ln 145-146):
"Unfortunately, there were not reported yet any applications of several types of graphene materials in a single aptasensor."
Comment: In Line 180, the references about using Graphene as carriers for Au and redox molecules should be given.
Response: The references [70,71] were added as requested.
Comment: The table summarized the most recent works using CNT and Graphene for aptasensors. It would be better that the authors could give more details about how the carbon materials was integrated with the aptamers. The typical scheme or Figures from the reported works should be added in this review.
Response: Typical schemes of signal generation are presented in Figures 8, 10 and 11. They cover all of them utilized for aptasensor signal detection.
Comment: The performance (for example, detection limits) of carbon nanomaterials based aptasensors listed in the table should be compared, or discussed in the Review.
Response: The limits of detection are presented in Tables 1 and 2 in fourth column. Short discussion comparing the limit of detections for certain type of aptasensors is presented (Ln 712-740) as follows:
"It is important to note that the sensitivity of most of the aptasensors based on carbon nanomaterials is extremely high and meets most requirements of medical diagnostics and environmental monitoring. Moreover, in some cases concerning the determination of organophosphate pesticide, the concentrations determined are so small that it is hardly to find the analytical problems correspond to their value. Indeed, the detection of profenofos on the level of 0.025 ng/mL [174] or malathion on the level of 0.1 fM [168] does not have sense in terms of food safety or contamination assessment. To some extent this refers also to determination of some metabolites like trypthophan and urea. One of the possible reason to reach lower and lower LOD values is to allow higher dilution of the samples and hence suppress matrix interference. However, on other cases, especially for cancer biomarkers detection, extremely high sensitivity of the aptasensrs described seems an important advantage due to opportunities of early diagnosis of cancer diseases and hopes for more successful therapy of such patients. Regarding relative influence of different modifiers on the analytical performance of aptasensors, only few analytes have been determined with various content of the surface layer. Some of such works (see determination of thrombin and CEA) were performed in the same research groups with rather insignificant changes of the measurement conditions. It can be concluded from the comparison of these results that the use of carbon nanomaterials in combination with Au nanoparticles or other catalytic systems provides better performance against ‘pure’ carbon nanomaterial. Then, the biochemical amplification mechanism also increased the sensitivity of the assay even to a higher extent that inclusion of additional inorganic components into the aptasensor assembly. It should be noted that such systems, being very sensitive, require much more reagents and extra stages so that the duration of the measurement cycle stands to about one hour. Together with requirements of thermosetting, this makes such measurement protocols incompatible with the biosensor idea assuming portable instrumentation with fast and rather simple measurement protocol. Such complication of the bioassay is rational if biomarkers crucially important for danger diseases diagnostics are detected. Regarding signal measurement mode, EIS shows much higher sensitivity of the response against voltammetry though the use of DPV technique can decrease this difference to acceptable levels. Meanwhile, EIS requires careful control of non-specific adsorption and can provide positive false in diagnostics of some biomarkers."
Reviewer 2 Report
In the manuscript authors describe series of carbon structures that are used for aptasensors construction. The manuscript may be published in Chemosensors after several corrections:
- I’m not sure why author compare fullerene and graphitized carbon nitride (g-C3N4) in figure 3 as they are totally different structures (and fullerene is even not mentioned in the paragraph)
- The title of Table 2 is “The characteristics of electrochemical aptasensors based on graphene materials (2016-2020)” but only three of them are based on graphene, all others are rGO or GO. Therefore in my opinion the title should be renamed according to the paragraph name “The characteristics of electrochemical aptasensors based on graphene and related materials (2016-2020)”
Author Response
We are grateful to the reviewers for very useful comments that allowed us to improve manuscript.
In the manuscript authors describe series of carbon structures that are used for aptasensors construction. The manuscript may be published in Chemosensors after several corrections:
Comment: I’m not sure why author compare fullerene and graphitized carbon nitride (g-C3N4) in figure 3 as they are totally different structures (and fullerene is even not mentioned in the paragraph)
Response: The structures of fullerene and graphitized carbon nitride were presented in one figure only in attempts to limit the number of figures. In accordance with the Reviewer comment, we have separated them and placed in two figures with corresponding description in the text.
Comment: The title of Table 2 is “The characteristics of electrochemical aptasensors based on graphene materials (2016-2020)” but only three of them are based on graphene, all others are rGO or GO. Therefore in my opinion the title should be renamed according to the paragraph name “The characteristics of electrochemical aptasensors based on graphene and related materials (2016-2020)”
Response: We agree with this comment. The title was modified as requested.
Reviewer 3 Report
The peer-reviewed article by Evtugyn et al. can be intersted to a wide range of specialist working in chemical analysis of the different substances with an use of aptasensors based on various carbon materials. The authors collected a lot of papers on this wide scientific area and they preapred an unique guide on succesfull applications of the aptasensors in the different areas of electrochemical analysis. In general, this review is scientifically correct, but often the authors don't cite the original papers and I marked some of these places in pdf-file. In addition, although I tried to correct the English used (see the attached pdf-file), the further its polishing is strongly desirable.
There are two physical questions on the text:
1). Page 4 (line 172): In arc discharge, carbon atoms are evaporated from solid precursors at 3000-3500°C.
First, I would like to note that the transition of the atoms from the solid phase into gaseous(plasma) phase is called sublimation and it would be more correct to use the verb «sublimated» instead of «evaporated». In addition, I recommend to correct the value of the temperature range in arc discharge during CNT synthesis. There is an excellent review on this topics: Neha Arora, N.N. Sharma, Arc discharge synthesis of carbon nanotubes: Comprehensive review, Diamond & Related Materials 50 (2014) 135–150.
2) Page 4 (line 173):In laser ablation, laser pulses ablate carbon target heated to 1200°C.
In addition to the data on the temperature of the carbon target, it would be desirable to add information about the much higher temperature in the laser plume. See for example: Kuo et al., Synthesis of Carbon Nanotubes by Laser Ablation of Graphites at Room Temperature, Jpn. J. Appl. Phys. Vol. 40 Part 1, No. 12, (2001) pp. 7147–7150.
Comments for author File: 
Comments.pdf
Author Response
We are grateful to the reviewers for very useful comments that allowed us to improve manuscript.
The peer-reviewed article by Evtugyn et al. can be interested to a wide range of specialist working in chemical analysis of the different substances with an use of aptasensors based on various carbon materials. The authors collected a lot of papers on this wide scientific area and they prepared an unique guide on successful applications of the aptasensors in the different areas of electrochemical analysis. In general, this review is scientifically correct, but often the authors don't cite the original papers and I marked some of these places in pdf-file. In addition, although I tried to correct the English used (see the attached pdf-file), the further its polishing is strongly desirable.
Response: We are very grateful to the reviewer for careful reading of manuscript and for important corrections. We have corrected all the mistakes mentioned in the pdf file as requested. Several references of original papers were included in the revised manuscript according to reviewers suggestions.
Comment: There are two physical questions on the text:
1). Page 4 (line 172): In arc discharge, carbon atoms are evaporated from solid precursors at 3000-3500°C.
First, I would like to note that the transition of the atoms from the solid phase into gaseous (plasma) phase is called sublimation and it would be more correct to use the verb «sublimated» instead of «evaporated». In addition, I recommend to correct the value of the temperature range in arc discharge during CNT synthesis. There is an excellent review on this topics: Neha Arora, N.N. Sharma, Arc discharge synthesis of carbon nanotubes: Comprehensive review, Diamond & Related Materials 50 (2014) 135–150.
Response: We agree with this comments and appreciate the reviewer's advice. We have substituted the word ‘evaporated’ with ‘sublimated’ as requested, changed the temperature interval to 4000 – 6000 K and included the review recommended (reference [70] in revised manuscript).
Comment: 2) Page 4 (line 173): In laser ablation, laser pulses ablate carbon target heated to 1200°C.
In addition to the data on the temperature of the carbon target, it would be desirable to add information about the much higher temperature in the laser plume. See for example: Kuo et al., Synthesis of Carbon Nanotubes by Laser Ablation of Graphites at Room Temperature, Jpn. J. Appl. Phys. Vol. 40 Part 1, No. 12, (2001) pp. 7147–7150.
Response: We agree with the reviewers comments. The following sentence was added: "In laser plume, the temperature can reach 4000 K" (Ln 188). The article recommended was included in the reference list as ref. [71].
