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Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite.

Das G, Yoon HH - Int J Nanomedicine (2015)

Bottom Line: The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds.Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C.The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biological Engineering, Gachon University, Seongnam, Gyeonggi-do, South Korea.

ABSTRACT
An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (μA · cm(-2)·mM(-1). The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

No MeSH data available.


Cyclic voltammogram.Notes: (A) Chronoamperometric curve obtained at different urea concentrations; (B) calibration curve of signal current vs urea concentration obtained after triplicate measurements; and (C) amperometric signal for minimum concentration of urea (50 µM) based on a signal/noise ratio of 3.
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f11-ijn-10-055: Cyclic voltammogram.Notes: (A) Chronoamperometric curve obtained at different urea concentrations; (B) calibration curve of signal current vs urea concentration obtained after triplicate measurements; and (C) amperometric signal for minimum concentration of urea (50 µM) based on a signal/noise ratio of 3.

Mentions: The amperometric response of the ITO/SG-PANI/Urs biosensor was analyzed through the current responses to varying urea concentration (0.12–20 mM) for a definite period of time (Figure 11A). The calibration plot (Figure 11B) indicates a broad linear range (0.12–12.3 mM), a correlation coefficient of 0.997, and a detection limit of 0.05 mM (0.140 mg/dL), based on the signal to noise ratio of ~3 (Figure 11C). A sensitivity of 0.85 µA·cm−2·mM−1 was obtained for the biosensor from the slope of the current/urea concentration calibration curve after triplicate measurements. The ITO/SG-PANI/Urs biosensor showed a rapid response to the change in urea concentration with a response time of ~5 seconds. The instantaneous response of the biosensors can be attributed to the quick diffusion of the NH4+ ions produced during urea hydrolysis toward the PANI surface through the large electrode/electrolyte interface. The porous structure of the biosensor allows low-barrier translational mass diffusion of the ionic species, which results in better utilization of the active sites of the enzyme (Figure 12). The electrochemical signal is generated by the SG-PANI film due to the association between graphene-SO3− and NH+ to form graphene-SO3−NH4+ (Figure 12), which causes dissociation of NH4+ into NH3 and H+. The proton liberated in this process protonates the imine unit of PANI, generating a radical cation (polaron/bipolaron structure). The interconnected network of PANI nanofibers on the graphitic structure ensures a faster transfer of the electrons, resulting in a fast response time (~5 seconds) for the biosensors compared to other reported values of doped intrinsically conducting polymers (Table 1). It is important to mention that the measured sensitivity was adequate, considering that the urea levels present in the human serum are approximately 1.7–8.3 mM.53


Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite.

Das G, Yoon HH - Int J Nanomedicine (2015)

Cyclic voltammogram.Notes: (A) Chronoamperometric curve obtained at different urea concentrations; (B) calibration curve of signal current vs urea concentration obtained after triplicate measurements; and (C) amperometric signal for minimum concentration of urea (50 µM) based on a signal/noise ratio of 3.
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Related In: Results  -  Collection

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f11-ijn-10-055: Cyclic voltammogram.Notes: (A) Chronoamperometric curve obtained at different urea concentrations; (B) calibration curve of signal current vs urea concentration obtained after triplicate measurements; and (C) amperometric signal for minimum concentration of urea (50 µM) based on a signal/noise ratio of 3.
Mentions: The amperometric response of the ITO/SG-PANI/Urs biosensor was analyzed through the current responses to varying urea concentration (0.12–20 mM) for a definite period of time (Figure 11A). The calibration plot (Figure 11B) indicates a broad linear range (0.12–12.3 mM), a correlation coefficient of 0.997, and a detection limit of 0.05 mM (0.140 mg/dL), based on the signal to noise ratio of ~3 (Figure 11C). A sensitivity of 0.85 µA·cm−2·mM−1 was obtained for the biosensor from the slope of the current/urea concentration calibration curve after triplicate measurements. The ITO/SG-PANI/Urs biosensor showed a rapid response to the change in urea concentration with a response time of ~5 seconds. The instantaneous response of the biosensors can be attributed to the quick diffusion of the NH4+ ions produced during urea hydrolysis toward the PANI surface through the large electrode/electrolyte interface. The porous structure of the biosensor allows low-barrier translational mass diffusion of the ionic species, which results in better utilization of the active sites of the enzyme (Figure 12). The electrochemical signal is generated by the SG-PANI film due to the association between graphene-SO3− and NH+ to form graphene-SO3−NH4+ (Figure 12), which causes dissociation of NH4+ into NH3 and H+. The proton liberated in this process protonates the imine unit of PANI, generating a radical cation (polaron/bipolaron structure). The interconnected network of PANI nanofibers on the graphitic structure ensures a faster transfer of the electrons, resulting in a fast response time (~5 seconds) for the biosensors compared to other reported values of doped intrinsically conducting polymers (Table 1). It is important to mention that the measured sensitivity was adequate, considering that the urea levels present in the human serum are approximately 1.7–8.3 mM.53

Bottom Line: The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds.Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C.The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biological Engineering, Gachon University, Seongnam, Gyeonggi-do, South Korea.

ABSTRACT
An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (μA · cm(-2)·mM(-1). The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

No MeSH data available.