A Self-Powered Acetaldehyde Sensor Based on Biofuel Cell

Nov 5, 2012 - urgent and significant. Inspired by the biological principle of feedback modulation, we have developed a novel and effective self-powere...
0 downloads 0 Views 1MB Size
Download PDF
Article pubs.acs.org/ac

A Self-Powered Acetaldehyde Sensor Based on Biofuel Cell Lingling Zhang, Ming Zhou, and Shaojun Dong* State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renming Street 5625, Changchun, Jilin, 130022, People’s Republic of China ABSTRACT: Acetaldehyde is recognized as a type of organic environmental pollutant all over the world, which makes the sensitive, rapid, simple and low-cost detection of acetaldehyde urgent and significant. Inspired by the biological principle of feedback modulation, we have developed a novel and effective self-powered device for aqueous acetaldehyde detection. In this self-powered device, an ethanol/air enzymatic biofuel cell (BFC) served as the core component, which showed the maximum power output density of 28.5 μW cm−2 at 0.34 V and the open circuit potential (Voc) of 0.64 V. The product of ethanol oxidation, acetaldehyde, would counteract the electrocatalysis at the bioanode and further decrease the power output of the BFC. Based on such principles, the fabricated acetaldehyde sensor exhibited excellent selectivity with wide linear range (5−200 μM) and low detection limit (1 μM), which conforms to the criteria provided by the World Health Organisation (WHO). In addition, the sensor fabrication is simple, fast, inexpensive, and user-friendly, and the detection process is convenient, efficient, and time-saving, requiring no complicated equipment. These make such self-powered acetaldehyde sensors feasible and practical for detecting aqueous acetaldehyde, particularly in the field of quality control and monitoring aimed at water resource protection.

A

determination of formaldehyde and acetaldehyde in food.5 However, most of the mentioned methods require derivatization agents, complicated operation, or expensive instruments, and they are not really suitable for wide applications, in particular for on-site monitoring. Electrochemical methods, because of the advantages of cost-efficiency, simple operation, and high sensitivity, are employed widely in chemical or biologic analyte determination.6 Enzymatic biofuel cells (BFCs), which are also referred to as bioelectrochemical fuel cells, are hybrid systems that combine the efficiency of electrochemical energy conversion with that of biocatalysis. They have drawn considerable attention and made many advanced and remarkable achievements in recent decades.7 As an efficient energy conversion technology, their development has not been confined only to cell assembling and performance improving, but also focused on their useful and potential application, i.e., power extracting from living creatures,8 miniaturization for low-cost, portable power devices on other matrixes,9 especially being used as the core components of self-powered sensors.10 Self-powered sensors based on BFCs are drawing increased attention, because of the capability for detection without external power sources, simplifying the fabrication process, minimizing the scale, and reducing the expense, which is especially beneficial to the miniaturization of detection devices. Herein, we have proposed

cetaldehyde, which is a ubiquitous organic compound, may cause water and atmosphere pollution, and directly threaten human health. Exogenous acetaldehyde inhalation may result in bronchitis, upper respiratory tract symptom, dottiness, protein denaturation, and even death. As the byproduct of cellular metabolism, it is considered as a possible human carcinogen for the reason that it can react avidly with genomic DNA, and accordingly induce cellular genotoxicity in living creatures.1 Also, acetaldehyde has been classified as a contaminant in drinking water by the United States Environmental Protection Agency (USEPA). Obviously, acetaldehyde detection is significant for both the environment and human beings, and the development of sensitive, rapid, simple, and low-cost devices for acetaldehyde detection is urgent and important. Toward this end, a variety of techniques and methods were applied in acetaldehyde detection. Tessini et al. employed a gas chromatograph coupled to a mass-selective detector and flame ionization detector (GC/MS/FID) and high-performance liquid chromatography coupled to ultraviolet−visible spectrum (HPLC-UV) for the detection of low-molecular-mass aldehydes in bio-oil.2 Solid-phase microextraction (SPME) coupled to other analytical techniques were also a common approach for aldehydes determination.3 Neng et al. exploited bar adsorptive microextraction (BAμE) for the determination of short-chain carbonyl compounds, which proved to be an effective method to monitor short-chain aldehydes and ketones in drinking water matrices.4 Zhang et al. adopted miniaturized capillary electrophoresis with electrochemical detection (mini-CE-ED) for the © 2012 American Chemical Society

Received: August 21, 2012 Accepted: November 5, 2012 Published: November 5, 2012 10345

dx.doi.org/10.1021/ac302414a | Anal. Chem. 2012, 84, 10345−10349

Analytical Chemistry

Article

Scheme 1. Principle for the Acetaldehyde Sensor Based on the Ethanol/Air BIofuel Cell (BFC)

could inhibit the kinetics of enzyme-catalytic ethanol electrooxidation.12 The mechanism is hypothesized to be the product suppression on the forward reaction rate of enzymatic catalysis, i.e., the catalytic current in electrocatalysis. In light of this particular behavior, a biosensing system has been designed for the determination of acetaldehyde reflected by the power output signal of the BFC. Compared with other detection techniques, the advantages of the present biosensor, such as fast response, simple operation, and reusability, may open a new pathway for analytical detection.

carbon nanotubes covalently binding with amine-terminated ionic liquid (CNTs-IL-NH2) serves as the electrode substrates, and alcohol dehydrogenase (ADH) and bilirubin oxidase (BOD) are immobilized on the anode and cathode, respectively. ADH is a zinc metalloenzyme catalyzing the reversible oxidation of primary short-chain alcohols to their corresponding carbonyl compounds using NAD+ or NADP+ as a cofactor.11 According to the previous reports, acetaldehyde

EXPERIMENTAL SECTION Reagents and Instruments. Alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae (E.C.1.1.1.1, ≥369 U mg−1), bilirubin oxidase (BOD) from Myrothecium verrucaria (E.C.1.10.3.2, 6 U mg−1), and chitosan (CAS, 9012-76-4) were purchased from Sigma. Ionic liquid (methylimidazole, note as IL) was purchased from Alfa Aesar. Multiwalled carbon nanotubes (CNTs) were obtained from Shenzhen Nanotech. Port. Co. Ltd. (Shenzhen, PRC) without further purification. CNTs-IL-NH2 was synthesized according to the reported method.13 NAD+ and NADH were obtained from Dingguo Reagent Company (Beijing, PRC). Ethanol, acetaldehyde, formaldehyde, acetic acid, acetone, and benzaldehyde were obtained from Beijing Chemical Reagent Company (Beijing, PRC). Phosphate buffer solution (PBS, 0.1 M, pH 7.0) was used as the supporting electrolyte. All other chemicals were of analytical grade and used as received. Ultrapure water was used throughout. Electrochemical measurements were made with an electrochemical workstation (Model CHI 832B, Shanghai Chenhua Instrument Corporation, China). Ag/AgCl electrode (saturated

an analytical strategy involving the regulation of the BFC performance caused by reversible kinetics suppression for the first time. The oxidized product at the bioanode is available to counteract the forward oxidation as well as disturb the enzymatic electrochemical equilibrium. The core component of this self-powered biosensor is a membrane-less ethanol/air BFC. As shown in Scheme 1,

■

Figure 1. (A) Polarization curves of the bioanode for ethanol oxidation in base solution containing 0 mM ethanol (curve a), 15 mM ethanol (curve b), and 30 mM ethanol (curve c). (B) Polarization curves of biocathode for O2 reduction in base solution saturated with N2 (curve a), air (curve b), and O2 (curve c). Scan rate is 1 mV s−1. (C) The dependence of the power output density on the potential of the BFC in different situation: the modified enzyme electrodes and with 30 mM ethanol as the biofuel (curve a); the modified enzyme electrodes and without the biofuel (curve b); and the CNTs-IL-NH2/GC electrodes and with 30 mM ethanol as the biofuel (curve c). (D) The stability of continuous operation at 0.34 V for 10 h. 10346

dx.doi.org/10.1021/ac302414a | Anal. Chem. 2012, 84, 10345−10349

Analytical Chemistry

Article

Figure 2. (A) The Voc response to acetaldehyde injection with different concentrations: 0 μM (curve a), 10 μM (curve b), and 100 μM (curve c). (B) The power output response to acetaldehyde injection with different concentrations: 0 μM (curve a), 10 μM (curve b), and 100 μM (curve c). (C) The power output response to the continuous acetaldehyde injection of different concentrations: 10, 10, 20, 20, 50, 100, 200, and 200 μM. Inset shows the power output response of the BFC to the continuous 1 μM acetaldehyde injection for six times. A fitting curve is shown in black. (D) The relationship between power change percentage (ΔP%) and acetaldehyde concentrations. Inset shows the linear function of the plot of ΔP% vs the logarithm of acetaldehyde concentrations.

BFC performance test. The quantitive relationship was established based on the variations of power output of BFC (the current output multiplied by the constant potential, 0.34 V) relied on different acetaldehyde concentrations added into the solution. The selectivity of the biosensing system was evaluated by operating this acetaldehyde sensor in the biofuel solution containing 500 μM possible interferents (i.e., formaldehyde, acetic acid, acetone, and benzaldehyde) into the solution of the well-operating BFCs and comparing the variation of the current-output value. To show the regeneration ability of the biosensing system, the chronoamperometry experiment was taken to record the inhibited and activated current of the operating BFC alternately. Here, fresh PBS containing 30 mM ethanol and 40 μM acetaldehyde were used as the activating reagent and the inhibiting reagent, respectively. Employing tap water with external target analyte and interferences addition (50 μM acetaldehyde, 100 μM formaldehyde, and 100 μM acetone) as the testing sample, five uniform sensing platforms were fabricated and the detection was repeated five times.

KCl) and a platinum wire electrode were used as the reference electrode and counter electrode, respectively. All of the experiments were carried out at room temperature. Ethanol/Air BFC Assembly and Measurement. The bioelectrodes of the assembling BFC was prepared as follows: before modification, glassy carbon electrodes (GC electrodes, 3 mm in diameter) were polished with 1.0-, 0.3-, and 0.05-μm alumina slurry and then were sonicated in ultrapure water and ethanol three times, respectively. Five microliters (5 μL) of 0.1 mg mL−1 CNTs-IL-NH2 was deposited dropwise onto a GC electrode and dried under infrared light, noted as the CNTs-ILNH2/GC electrode. Then, 5 μL of ADH solution (1 mg mL−1 dissolved in PBS containing 1% chitosan) was spread onto the CNTs-IL-NH2/GC electrode to fabricate the bioanode (i.e., ADH/CNTs-IL-NH2/GC electrode); similarly, the biocathode (i.e., BOD/CNTs-IL-NH2/GC electrode) was fabricated by spreading 5 μL of BOD solution onto the CNTs-IL-NH2/GC electrode. After drying bioanode and biocathode at 4 °C overnight, the ethanol/air BFC was constructed and then operated in a base solution (i.e., 0.1 M, pH 7.0 PBS, with 5 mM NAD+) containing 30 mM ethanol. Acetaldehyde-Sensing Platform Construction and Evaluation. To demonstrate the qualitative influence of acetaldehyde on the assembled BFC, we employed the Voc and power output of the BFC as the testing items. The Voc data were obtained in a steady open-circuit potential under normal and inhibited conditions. Subsequently, the polarization curves were taken from Voc to 0 V with a scan rate of 1 mV/s. To develop an acetaldehyde-sensing platform, the BFC apparatus was operated in 0.10 M pH 7.0 PBS containing 5 mM NAD+ and 30 mM ethanol under a constant potential, 0.34 V, which is the corresponding potential to the Pmax of BFC obtained in a

■

RESULTS AND DISCUSSION Before assembling the BFC devices, we first investigated the electrocatalysis behavior at the bioanode and biocathode. As shown in Figure 1A, the electrocatalytic oxidation of ethanol commences at −0.11 V and the catalytic current reaches ∼100 μA cm−2 at 30 mM ethanol concentration. Also, in 0.1 M pH 7.0 PBS saturated with air, the onset potential of electrocatalytic dioxygen reduction is 0.54 V and the current reaches a plateau with 160 μA cm−2 at 0.4 V (Figure 1B, curve b), which is higher than the catalytic current at the bioanode. This indicates that the kinetics at the bioanode is the limiting factor and, therefore, 10347

dx.doi.org/10.1021/ac302414a | Anal. Chem. 2012, 84, 10345−10349

Analytical Chemistry

Article

controlling the bioanode reaction would influence the cell performance. Figure 1C reveals that the Voc of the BFC is 0.64 V and the maximum power density (Pmax) reaches 28.5 μW cm−2 at 0.34 V. Figure 1D indicates that the power output loses 10% after continuous operation for 10 h. Because the subsequent concentration-dependent measurement could be completed within less than 1 h, we consider the power output to remain almost constant during this period. Five repeated assemblies and characterizations of the BFCs show that the relative standard deviation (RSD) of the power output is ∼0.8%. Moreover, the present BFC could almost retain its initial performance in 4 °C for at least one week (data not shown). Figures 2A and 2B depict that both the cell Voc and power density are able to respond to different concentrations of acetaldehyde. In the absence of acetaldehyde, the Voc maintains a constant value of 0.64 V (Figure 2A (trace a)) and the Pmax reaches 28.5 μW cm−2 (Figure 2B (curve a)). When 10 μM acetaldehyde was added, the Voc and Pmax values decrease to 0.63 V (see curve b in Figure 2A) and 25.6 μW cm−2 (see curve b in Figure 2B), respectively. In the bioanode reaction, ADH catalyzes the oxidation of substrate, ethanol, to acetaldehyde selectively. Because of the reversibility of enzymatic reaction, the increase in acetaldehyde ratio is capable of improving the backward catalytic rate as well as reducing the forward rate, which lead to inferior BFC performance. The Voc and Pmax values decline further with the injection of 100 μM acetaldehyde (see curve c in Figures 2A and 2B). The corresponding relationship between the BFC performance and acetaldehyde concentration is attractive, and the idea employing the biological regulation mechanism to modulate the BFC performance has not been reported previously, according to the best of our knowledge. Considering the rapid response and the consecutive operability, the concentration-dependent assay was carried out by recording the power output change of the BFC operated at 0.34 V, shown in Figure 2C. After the injection of 30 mM ethanol, the assembled BFC generated steady power output density. Treating the BFC with incremental concentrations of acetaldehyde (10, 20, 40, 60, 110, 210, 410, and 610 μM), the power decreased gradually, in accordance with the increase of acetaldehyde concentrations. The relevance between the variation percentage and the corresponding acetaldehyde concentration was plotted in Figure 2D. Notably, the power of the BFC is linear over the logarithm of acetaldehyde concentration ranging from 5 μM to 200 μM (R = 0.998) (Figure 2D, inset). The detection limit is 1 μM, which is lower than 0.2 mg/L (4.5 μM), the maximum acceptable concentration according to the health and safety guide (HSG) published by the World Health Organisation (WHO).14 A prominent and important advantage of this sensing platform is that the component electrodes could be renewed by simply replacing with base solution, which testifies for the reversible inhibition of acetaldehyde on the BFC performance, as well as the maintenance of enzyme activity. As described in Figure 3, the BFC initially operated at 0.34 V in base solution containing a 30 mM solution. With a 30 mM ethanol injection at point “a”, the BFC generated a higher power output density immediately. Acetaldehyde was added until a steady and durable value is achieved (point “b”). The power signal decreased as the same situation in Figure 2B, as expected. At point “c”, we updated the fresh base solution and, consequently, the device was reset to the initial condition. Repeating the

Figure 3. Power output signal recorded in operation of the assembled BFC with injecting different chemicals: (a) 30 mM ethanol, (b) 40 μM acetaldehyde, and (c) changing base solution.

procedures of ethanol and acetaldehyde injection successively, the BFC was capable of fluctuating rapidly, in response to the activation and inhibition. These suggested the practicality of such a self-powered acetaldehyde sensor. The selectivity of the self-powered acetaldehyde sensor was evaluated by testing the effect of various interferents on the cell power output. Normalizing the power decline caused by 500 μM acetaldehyde as having a value of 1, we compared the decline percentage caused by equimolar possible interferents in Figure 4. This result demonstrates that all of the possible

Figure 4. Effect of different interferences; the analyte concentration, as well as that of all the interfering agents, is 500 μM.

interferents can rarely affect the power output, suggesting the excellent selectivity of this acetaldehyde detecting platform. In order to estimate the feasibility, we measured the aqueous sample mixture (containing 50 μM acetaldehyde, 100 μM formaldehyde, and 100 μM acetone in tap water) with five sensors, and obtained a relative standard deviation (RSD) of 3.5% for 5 sensors, demonstrating the good reproducibility in real sample determination. Without the use of a derivatization agent and expensive instruments, the proposed method is sensitive, cost-efficient, time-saving, and user-friendly. Therefore, it is favorable for the self-powered sensors to expand their application in real sample determination, especially in the field of quality control and monitoring aimed at water resource protection.

■

CONCLUSION In the present work, we have demonstrated a novel type of user-friendly, low-cost, and self-powered acetaldehyde sensor based on the regulation of the biofuel cell (BFC) performance caused by kinetics suppression. The sensor is able to detect an 10348

dx.doi.org/10.1021/ac302414a | Anal. Chem. 2012, 84, 10345−10349

Analytical Chemistry

Article

acetaldehyde concentration of 5−200 μM, with a detection limit of 1 μM, which conforms to the criteria provided by teh World Health Organisation (WHO).14 In addition, the excellent selectivity favors it to distinguish the analyte from other carbonyl compounds. Thus, these imply the potential application in real sample determination. Also, the inherent superiority of the mechanism and the excellent selectivity make this type of biosensor potentially feasible and practical in quality control and monitoring aimed at water resource protection.

■

Bourdillon, C. Biotechnol. Bioeng. 1991, 38, 788−796. (c) Indrati, R.; Ohta, Y. Can. J. Microbiol. 1992, 38, 953−957. (13) (a) Guo, S. J.; Dong, S. J.; Wang, E. K. Adv. Mater. 2010, 22, 1269−1272. (b) Yang, H. F.; Shan, C. S.; Li, F. H.; Han, D. X.; Zhang, Q. X.; Niu, L. Chem. Commun. 2009, 3880−3882. (c) Guo, S. J.; Wen, D.; Zhai, Y. M.; Dong, S. J.; Wang, E. K. Biosens. Bioelectron. 2011, 26, 3475−3481. (14) http://www.inchem.org/documents/hsg/hsg/hsg90_e.htm, 1994.

AUTHOR INFORMATION

Corresponding Author

*Tel.: (+86) 431-85262101. Fax: (+86) 431-85689711. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by National Natural Science Foundation of China (Nos. 20935003 and 21075116) and the 973 Project (Nos. 2010CB933603 and 2011CB911002).

■

REFERENCES

(1) (a) O’Brien, P. J.; Siraki, A. G.; Shangari, N. Crit. Rev. Toxicol. 2005, 35, 609−662. (b) Stein, S.; Lao, Y. B.; Yang, I. Y.; Hecht, S. S.; Moriya, M. Mutat. Res.−Genet. Toxicol. Environ. Mutagen. 2006, 608, 1−7. (c) Chen, L.; Wang, M. Y.; Villalta, P. W.; Luo, X. H.; Feuer, R.; Jensen, J.; Hatsukami, D. K.; Hecht, S. S. Chem. Res. Toxicol. 2007, 20, 108−113. (2) Tessini, C.; Muller, N.; Mardones, C.; Meier, D.; Berg, A.; von Baer, D. J. Chromatogr. A 2012, 1219, 154−160. (3) Khorrami, A. R.; Narouenezhad, E. Talanta 2011, 86, 58−63. (4) Neng, R.; Nogueira, J. M. Anal. Bioanal. Chem. 2010, 398, 3155− 3163. (5) Zhang, D. L.; Zhang, J. B.; Li, M. J.; Li, W. L.; Aimaiti, G.; Tuersun, G.; Ye, J. N.; Chu, Q. C. Food Chem. 2011, 129, 206−212. (6) Zhou, M.; Dong, S. J. Acc. Chem. Res. 2011, 44, 1232−1243. (7) Zebda, A.; Gondran, C.; Le Goff, A.; Holzinger, M.; Cinquin, P.; Cosnier, S. Nat. Commun. 2011, 2, 370. (8) (a) Cinquin, P.; Gondran, C.; Giroud, F.; Mazabrard, S.; Pellissier, A.; Boucher, F.; Alcaraz, J. P.; Gorgy, K.; Lenouvel, F.; Mathe, S.; Porcu, P.; Cosnier, S. PLoS. One. 2010, 5, e10476. (b) Halamkova, L.; Halamek, J.; Bocharova, V.; Szczupak, A.; Alfonta, L.; Katz, E. J. Am. Chem. Soc. 2012, 134, 5040−5043. (c) Rasmussen, M.; Ritzmann, R. E.; Lee, I.; Pollack, A. J.; Scherson, D. J. Am. Chem. Soc. 2012, 134, 1458−1460. (d) Szczupak, A.; Halámek, J.; Halámková, L.; Bocharova, V.; Alfonta, L.; Katz, E. Energy Environ. Sci. 2012, 5, 8891−8895. (9) Zhang, L. L.; Zhou, M.; Wen, D.; Bai, L.; Lou, B. H.; Dong, S. J. Biosens. Bioelectron. 2012, 35, 155−159. (10) (a) Katz, E.; Buckmann, A. F.; Willner, I. J. Am. Chem. Soc. 2001, 123, 10752−10753. (b) Germain, M. N.; Arechederra, R. L.; Minteer, S. D. J. Am. Chem. Soc. 2008, 130, 15272−15273. (c) Amir, L.; Tam, T. K.; Pita, M.; Meijler, M. M.; Alfonta, L.; Katz, E. J. Am. Chem. Soc. 2009, 131, 826−832. (d) Deng, L.; Chen, C. G.; Zhou, M.; Guo, S. J.; Wang, E. K.; Dong, S. J. Anal. Chem. 2010, 82, 4283−4287. (e) Zhou, M.; Zhou, N.; Kuralay, F.; Windmiller, J. R.; Parkhomovsky, S.; ValdesRamirez, G.; Katz, E.; Wang, J. Angew. Chem., Int. Ed. Engl. 2012, 51, 2686−2689. (f) Zhou, M.; Wang, J. Electroanalysis 2012, 24, 197−209. (11) (a) Eklund, H.; Plapp, B. V.; Samama, J. P.; Branden, C. I. J. Biol. Chem. 1982, 257, 4349−4358. (b) Bryant, F. O.; Wiegel, J.; Ljungdahl, L. G. Appl. Environ. Microb. 1988, 54, 460−465. (12) (a) Yoon, S. Y.; Noh, H. S.; Kim, E. H.; Kong, K. H. Comput. Biochem. Phys. B 2002, 132, 415−422. (b) Laval, J. M.; Moiroux, J.; 10349

dx.doi.org/10.1021/ac302414a | Anal. Chem. 2012, 84, 10345−10349