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FIGURE 4 The calibration curve of GE/BOTT/Lac within the optimum conditions. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 4 The calibration curve of GE/BOTT/Lac within the optimum conditions. [Color figure can be viewed at wileyonlinelibrary.com]

Related Figures (7)

SCHEME 1A typical biosensor fabrication architecture. [Color figure can be viewed at wileyonlinelibrary.com] All chemicals used in organic synthesis were purchased from Sigma/Aldrich. Gluteraldehyde (GA) as the crosslinking agent and catechol were purchased from Sigma-Aldrich. Laccase (Lac; EC 1.10.3.2, from Trametes versicolor, 21.8 unit mg”) was obtained from Sigma. 2,5-Bis(tributylstannyl)thiophene and = 2,6-bis(trimethylstannyl)-4,8-bis(2-ethylhexyloxy)benzo [1,2-b:4,5-b’]dithiophene were used without further PUCEMOL dla PHEMUME COMIMOUTUS dre LOVULLECU do LUAIL CLIVILOLI” mental pollutants in the environment. Among phenolic com- pounds, pyrocatechol and catechol (1,2-dihydroxybenzene) are phenolic compounds having hazardous effects on plants, ani- mals, and human health.’” Additionally, due to their highly resistant properties to biotic and abiotic degradation they remain with toxic levels in the environment. Thus, in order to evaluate their toxicity in samples with high selectivity and sen- sitivity, there is a big demand for new methods. There are clas- sical methods for detection of them using analytical methods such as spectrophotometry, chemical, and gas chromatographic principles.‘*1° Due to some limitations in these methods (rela- tively complex instrumentation, needing preconcentration steps, highly expensive and time-consuming, etc.), there is a big need for new methods in order to handle such problems. Bio- sensors based on the combination of biological molecules with a suitable transducer provide a great route to detect phenolic compounds in environmental control and protection. The prop- erties of fast response, high selectivity and sensitivity, low cost, and simplicity make biosensors ideal sensing systems to moni- tor the phenolic compounds in the environment. Laccase (Lac), tyrosinase, and peroxidase biosensors have attracted great attention in the detection of phenolic compounds. Among these three enzymes, the biosensors prepared with laccase are gener- ally the most sensitive one to phenols.*° Laccase (Lac, benzenediol:oxygen oxidoreductase, EC 1.10.3.2) is a glycopro- tein where active sites are characterized by four copper atoms per monomer distributed in three redox sites. Different amper- ometric laccase biosensors have been utilized for quantifica- tions of phenolic compounds in different samples.2)-*° Brondani et al. describe the synthesis and characterization of polyethyleneimine (PEI)-coated gold nanoparticles (PEI-AuNPs) in order to construct laccase biosensor.*° They reported that such system shows good sensor properties with the help of the combination of PEI and AuNPs. With this combination, the opti- mized biosensor achieved the limits of detection (LODs) for the phenolic compounds (0.03 pM for catechol). In a similar work, a novel kind of fluorine and nitrogen codoped carbon dots
SCHEME 1A typical biosensor fabrication architecture. [Color figure can be viewed at wileyonlinelibrary.com] All chemicals used in organic synthesis were purchased from Sigma/Aldrich. Gluteraldehyde (GA) as the crosslinking agent and catechol were purchased from Sigma-Aldrich. Laccase (Lac; EC 1.10.3.2, from Trametes versicolor, 21.8 unit mg”) was obtained from Sigma. 2,5-Bis(tributylstannyl)thiophene and = 2,6-bis(trimethylstannyl)-4,8-bis(2-ethylhexyloxy)benzo [1,2-b:4,5-b’]dithiophene were used without further PUCEMOL dla PHEMUME COMIMOUTUS dre LOVULLECU do LUAIL CLIVILOLI” mental pollutants in the environment. Among phenolic com- pounds, pyrocatechol and catechol (1,2-dihydroxybenzene) are phenolic compounds having hazardous effects on plants, ani- mals, and human health.’” Additionally, due to their highly resistant properties to biotic and abiotic degradation they remain with toxic levels in the environment. Thus, in order to evaluate their toxicity in samples with high selectivity and sen- sitivity, there is a big demand for new methods. There are clas- sical methods for detection of them using analytical methods such as spectrophotometry, chemical, and gas chromatographic principles.‘*1° Due to some limitations in these methods (rela- tively complex instrumentation, needing preconcentration steps, highly expensive and time-consuming, etc.), there is a big need for new methods in order to handle such problems. Bio- sensors based on the combination of biological molecules with a suitable transducer provide a great route to detect phenolic compounds in environmental control and protection. The prop- erties of fast response, high selectivity and sensitivity, low cost, and simplicity make biosensors ideal sensing systems to moni- tor the phenolic compounds in the environment. Laccase (Lac), tyrosinase, and peroxidase biosensors have attracted great attention in the detection of phenolic compounds. Among these three enzymes, the biosensors prepared with laccase are gener- ally the most sensitive one to phenols.*° Laccase (Lac, benzenediol:oxygen oxidoreductase, EC 1.10.3.2) is a glycopro- tein where active sites are characterized by four copper atoms per monomer distributed in three redox sites. Different amper- ometric laccase biosensors have been utilized for quantifica- tions of phenolic compounds in different samples.2)-*° Brondani et al. describe the synthesis and characterization of polyethyleneimine (PEI)-coated gold nanoparticles (PEI-AuNPs) in order to construct laccase biosensor.*° They reported that such system shows good sensor properties with the help of the combination of PEI and AuNPs. With this combination, the opti- mized biosensor achieved the limits of detection (LODs) for the phenolic compounds (0.03 pM for catechol). In a similar work, a novel kind of fluorine and nitrogen codoped carbon dots
SCHEME 2 Synthetic pathway of the corresponding polymer.
SCHEME 2 Synthetic pathway of the corresponding polymer.
FIGURE 1 The effect of the important factors [(a) polymer amount, (b) enzyme amount, and (c) pH] on biosensor response.
FIGURE 1 The effect of the important factors [(a) polymer amount, (b) enzyme amount, and (c) pH] on biosensor response.
FIGURE 2 Cyclic voltammograms of with and without enzyme modified surfaces on GEs. [Color figure can be viewed at wileyonlinelibrary.com]
FIGURE 2 Cyclic voltammograms of with and without enzyme modified surfaces on GEs. [Color figure can be viewed at wileyonlinelibrary.com]
FIGURE 3 SEM images of the modified surfaces: (a) GE/BOTT and (b) GE/BOTT/Lac. The interference effects on the biosensor response were investigated and some potential substrates (ethanol, uric acid, ascorbic acid, glucose) were injected into the reaction medium [Fig. 5(a)]. The response was recorded by exposing the sensor in a 0.01 mM substrates with the interferants. The results showed that negligible signals were obtained for the related interfering substances whereas stable and accurate signal was created for catechol (Fig. 5). This high sensitivity toward cate- chol and less interference effect from other agents shows that the proposed biosensor could be good alternative for cate- chol detection without any significant interference coming from the substances. Moreover, the effect of the different Other additional important biosensor parameters (repeatabil- ity and operation stability) were also examined. The opera- tional stability of the sensor was examined using a freshly prepared electrode at optimum conditions to catechol solution and assessed its amperometric responses for 10 times for a period of 3 h successively. It was observed that the electrode retained 98% of its initial response at the end of the 10 mea- surements. The standard deviation (-+-SD) of 10 measurements was calculated as +0.081. These promising results indicate that enzyme leakage on the electrode surface was negligible.
FIGURE 3 SEM images of the modified surfaces: (a) GE/BOTT and (b) GE/BOTT/Lac. The interference effects on the biosensor response were investigated and some potential substrates (ethanol, uric acid, ascorbic acid, glucose) were injected into the reaction medium [Fig. 5(a)]. The response was recorded by exposing the sensor in a 0.01 mM substrates with the interferants. The results showed that negligible signals were obtained for the related interfering substances whereas stable and accurate signal was created for catechol (Fig. 5). This high sensitivity toward cate- chol and less interference effect from other agents shows that the proposed biosensor could be good alternative for cate- chol detection without any significant interference coming from the substances. Moreover, the effect of the different Other additional important biosensor parameters (repeatabil- ity and operation stability) were also examined. The opera- tional stability of the sensor was examined using a freshly prepared electrode at optimum conditions to catechol solution and assessed its amperometric responses for 10 times for a period of 3 h successively. It was observed that the electrode retained 98% of its initial response at the end of the 10 mea- surements. The standard deviation (-+-SD) of 10 measurements was calculated as +0.081. These promising results indicate that enzyme leakage on the electrode surface was negligible.
TABLE 1 Comparing LOD, Sensitivity and Linear Range to Other Laccase Biosensors considerably lower than the current response observed for catechol. It can be concluded that the proposed system is highly specific to catechol.
TABLE 1 Comparing LOD, Sensitivity and Linear Range to Other Laccase Biosensors considerably lower than the current response observed for catechol. It can be concluded that the proposed system is highly specific to catechol.
FIGURE 5 Effect of some substrates and phenol derivatives (0.01 mM) on the biosensor response at —0.3V in pH 7.0 phosphate buffer. [Color figure can be viewed _ at wileyonlinelibrary.com] NR, not reported.
FIGURE 5 Effect of some substrates and phenol derivatives (0.01 mM) on the biosensor response at —0.3V in pH 7.0 phosphate buffer. [Color figure can be viewed _ at wileyonlinelibrary.com] NR, not reported.
Related topics:
Conjugated PolymersElectrochemical Biosensorsbiological applications of polymers
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