Elsevier

Biosensors and Bioelectronics

Volume 52, 15 February 2014, Pages 277-280
Biosensors and Bioelectronics

Short communication
A sensitive and reliable dopamine biosensor was developed based on the Au@carbon dots–chitosan composite film

https://doi.org/10.1016/j.bios.2013.09.003Get rights and content

Highlights

  • The Au@carbon dots were used for good electrochemical signal with good biocompatibility.

  • Highly sensitive and selective detection of dopamine by the Au@CDs–CS/GCE.

  • This method was applied to the detection of DA content in its injection with satisfactory results.

Abstract

A novel composite film of Au@carbon dots (Au@CDs)–chitosan (CS) modified glassy carbon electrode (Au@CDs–CS/GCE) was prepared in a simple manner and applied in the sensitive and reliable determination of dopamine (DA). The CDs had carboxyl groups with negative charge, which not only gave it have good stability but also enabled interaction with amine functional groups in DA through electrostatic interaction to multiply recognize DA with high specificity, and the Au nanoparticle could make the surface of the electrode more conductive. Compared with the bare GCE, CS/GCE, and CDs–CS/GCE electrodes, the Au@CDs–CS/GCE had higher catalytic activity toward the oxidation of DA. Furthermore, Au@CDs–CS/GCE exhibited good ability to suppress the background current from large excess ascorbic acid (AA) and uric acid (UA). Under the optimal conditions, selective detection of DA in a linear concentration range of 0.01–100.0 μM was obtained with the limit of 0.001 μM (3S/N). At the same time, the Au@CDs–CS/GCE was also applied to the detection of DA content in DA's injection with satisfactory results, and the biosensor could keep its activity for at least 2 weeks.

Introduction

Acting as one of the excitatory neurotransmitters, dopamine (DA) plays an important role in several physiological events such as behavior, mood, and movement. It is also involved in some diseases and in drug addiction. In addition, DA is available for intravenous medication, which acts on the sympathetic nervous system, to produce effects such as increasing heart rates and blood pressure (Ji et al., 2012, Suzuki et al., 2013, Wightman, 2006, Sulzer, 2011, Goldberg, 1972). Hence, determination of DA in vivo/vitro becomes increasingly important in clinical medical practice. Tremendous efforts have been made over the last 30 years to detect it, such as high performance liquid chromatography (Muzzi et al., 2008, Carrera et al., 2007), ultraviolet–visible spectrophotometry (Barreto et al., 2008), capillary electrophoresis (Thabano et al., 2009, Li et al., 2010), liquid chromatography–electrospray tandem mass spectrometry (El-Beqqali et al., 2007), fluorescence spectrometry (Khattar and Mathur, 2013, Chen et al., 2011), etc. Compared with other described methods, the direct electrochemical method for DA analysis, as a simple, rapid, and sensitive alternative, is drawing increasing attention. However, on the bare glassy carbon electrode (GCE) the coexisting compounds such as uric acid (UA) or ascorbic acid (AA) in the biological samples can cause great interference due to the similar oxidation potential close to that of DA (Liu et al., 2013, Zhang et al., 2005). In addition, the accumulation of the oxidation product of AA or UA on electrode surface may lead to the electrode fouling with poor selectivity and reproducibility (Gonon et al., 1980). To resolve this problem, various materials have been employed to elaborate the surface of working electrodes or as the electrode materials, including boron-doped carbon nanotubes (Deng et al., 2009), graphene (Kim et al., 2010), gold nanoparticle (Raj et al., 2003), single wall carbon nanotubes (Habibi et al., 2011), Cu2O/graphene (Zhang et al., 2011), Au nanoparticle–polyaniline nanocomposite layers (Stoyanova et al., 2011), multiwall carbon nanotubes (Alothman et al., 2010), hollow nitrogen-doped carbon microspheres (Xiao et al., 2011), and so on. Although most of these systems contributed to the detection of dopamine, these modified materials had either limitations with aspect to sensitivity or the material synthesis was sophisticated and expensive. Consequently, it is highly desirable to develop a sensor that is not only sensitive, selective and reliable but also simple, practical and economical in biological, pharmacological and toxicological fields.

For biosensing electrodes, Au nanoparticle is an excellent choice due to its conductivity, stability, biocompatibility and large surface area (Hsu et al., 2012). Carbon dots (CDs) as a class of ‘zero-dimensional’ carbon nanomaterials have recently received considerable attention because of their advantageous characteristics. Compared with conventional semiconductor quantum dots, CDs are superior in terms of low cytotoxicity, excellent biocompatibility, simple synthesis, economy and remarkable conductivity (Liu et al., 2012, Dai et al., 2012, Chen et al., 2013). The CDs can provide abundant carboxyl groups at the surface which can significantly enhance the redox response of dopamine. In this paper, we reported the synthesis of Au@carbon dots (Au@CDs), and the Au@CDs nanostructures could be used as electrochemical labels with signal amplification technique as the CDs could increase surface area of the electrode and Au nanoparticle could make the surface of the electrode more conductive. Then a novel composite film of Au@CDs–chitosan (CS) modified GCE (Au@CDs–CS/GCE) was prepared, and introduced it into a sensor for the rapid, simple and sensitive determination of DA. Under the optimal conditions good linearity was observed between the differential pulse voltammetric peak current and the concentration of DA in the range from 0.01 μM to 100 μM in a pH 7.0 phosphate buffer solution. Meanwhile, the Au@CDs–CS/GCE was applied to the detection of DA content in injection solution.

Section snippets

Reagents and instrumentation

Sucrose, chitosan, chloroauric acid and dopamine were obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Oil acid, glacial acetic acid, ascorbic acid, citric acid and polyethylene glycol-200 were purchased from Xilong Chemical Co., Ltd. (Guangdong, China). Phosphate buffer solution was from Shanghai Kangyi Instrument Co., Ltd. (Shanghai, China). All other reagents are analytical reagents. Nanopure deionized and distilled water (18.2 MΩ) was used throughout all experiments.

Characterization of CDs, Au@CDs and CDs–CS/GCE

The morphology of CDs (see Fig. S1A in the Supplementary materials) and Au@CDs (see Fig. S1B in the Supplementary materials) was characterized by TEM; typical UV–vis absorption spectra of CDs (a), Au (b) and Au@CDs (c) was shown in Fig. S1C (see Fig. S1C in the Supplementary materials). The Au@CDs had strong absorption bands at 282 nm and 536 nm. These values are consistent with previous reports (Chen et al., 2013, Luo et al., 2012).

AFM images of bare GCE and Au@CDs–CS/GCE film are shown in Fig.

Conclusions

In this study, we developed and characterized a new DA sensor based on the Au@CDs–CS/GCE electrode with high sensitivity, nice specificity and good stability. Under the optimal conditions, selective detection of DA in a linear concentration range of 0.01–100.0 μM was obtained with the limit of 0.001 μM (3S/N). Furthermore, Au@CDs–CS/GCE electrode exhibited good ability to suppress the background current from large excess AA and UA. Meanwhile, the Au@CDs–CS/GCE was applied also to the detection of

Acknowledgments

This project was supported by the Science and Technology Foundation of the National General Administration of Quality Supervision in China (2012QK053), the Fujian Province Natural Science Foundation (2012D136), and the Minnan Normal University Graduate Students' Scientific Research Projects (No. 1300-1314).

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