Elsevier

Talanta

Volume 80, Issue 1, 15 November 2009, Pages 403-406
Talanta

Short communication
Glucose biosensor based on immobilization of glucose oxidase in platinum nanoparticles/graphene/chitosan nanocomposite film

https://doi.org/10.1016/j.talanta.2009.06.054Get rights and content

Abstract

The bionanocomposite film consisting of glucose oxidase/Pt/functional graphene sheets/chitosan (GOD/Pt/FGS/chitosan) for glucose sensing is described. With the electrocatalytic synergy of FGS and Pt nanoparticles to hydrogen peroxide, a sensitive biosensor with a detection limit of 0.6 μM glucose was achieved. The biosensor also has good reproducibility, long-term stability and negligible interfering signals from ascorbic acid and uric acid comparing with the response to glucose. The large surface area and good electrical conductivity of graphene suggests that graphene is a potential candidate as a sensor material. The hybrid nanocomposite glucose sensor provides new opportunity for clinical diagnosis and point-of-care applications.

Introduction

Graphene has recently emerged as an interesting material in a myriad of applications because of its unique mechanical and electronic properties [1], [2], [3], [4], [5]. Most of the graphene studies have focused on its physical properties, such as its electronic properties, and these studies have demonstrated some applications in gas sensors [6], [7] and pH sensors [8]. However, using graphene for biosensors has not received much attention. Graphene exhibits excellent electrical conductivity, high surface area, and strong mechanical strength [2], [4], [9]. Such properties indicate that graphene may be a good support for electrocatalysts. Recently, we developed a new approach for producing functionalized graphene sheets (FGSs) in mass quantities through the thermal expansion of graphite oxide to yield single graphene sheets with epoxy, hydroxyl, and carboxyl groups as well as Stone-Wales and 5–8–5 lattice defects [10]. Such functional groups and their lattice defects may play a significant role in preparing graphene-based electrocatalysts. Furthermore, these FGSs are more dispersible and biocompatible than other carbon-based materials due to their functional groups. These advantages of FGSs make them an ideal material for sensor and fuel cell applications. In fact, due to their planar morphology and thus larger accessible surface area, FGSs may perform better than any other carbon-based electrode as a sensor material. Another advantage of graphene is its potential low manufacturing cost as compared to other nanostructured carbon materials, such as carbon nanotubes. Recently, graphene has been used as electrode material for direct electrochemistry of glucose oxidase, battery, and fuel cell [11], [12], [13].

Noble nanoparticles (NPs), such as platinum, exhibit electrocatalytic behavior to hydrogen peroxide (H2O2) and have been widely used for sensing applications [14], [15], [16]. It will be attractive to prepare nanoparticle-functionalized FGS, e.g., platinum nanoparticles (Pt NP)/FGS nanocomposite, because such a functionalized FGS may generate synergy on electrocatalytic activity and thus enhance the sensitivity of the biosensor.

In this work, we report a FGS-based bionanocomposite film and demonstrate its application for sensitive glucose sensing. This bionanocomposite film was prepared by the following routes: chemically controlled modification of FGSs by electrodeposition of Pt NPs followed by physical modification of the Pt/FGS nanocomposite with enzymes. The FGS used here was prepared as described elsewhere [10]. The FGSs were first dispersed in a solution containing 0.2% chitosan and then cast on a glassy-carbon electrode (GCE). By using the potentiostatic electrodeposition in a platinum-containing solution, platinum nanoparticles were modified on the FGS/chitosan/GCE. Then glucose oxidase (GOD) was immobilized on Pt/FGS/chitosan/GCE, forming a bionanocomposite film.

Section snippets

Chemicals

GOD, d-glucose, chitosan, phosphate buffer saline, potassium chloride, acetic acid, chloroplatinic acid, sulfuric acid, H2O2, ascorbic acid, and uric acid were all purchased from Sigma–Aldrich (St. Louis, USA). All solutions used in the experiments were prepared with ultra-pure water (18.3  cm, Nanopure, Barnstead, USA).

Materials

The graphene used in our study was made by thermal exfoliation of graphite oxide [10], which starts with the chemical oxidation of graphite flakes to increase the c-axis spacing

Results and discussion

The chitosan dispersed FGSs were prepared and characterized with TEM. Fig. 1(A) shows an image of FGSs dispersed in chitosan. As shown in this figure, the FGSs exhibit wrinkled graphene sheets. This wrinkled nature of FGSs is highly beneficial in maintaining a high surface area on the electrode since the sheets cannot readily collapse back to a graphitic structure. The inset in Fig. 1(A) displays a selected-area electron diffraction (SAED) of the nanocomposite material, yielding a double

Conclusion

We present a novel bionanocomposite film consisting of GOD/Pt/FGS/chitosan for glucose sensing. The biosensor exhibits good sensitivity with a detection limit of 0.6 μM glucose. Such a sensitivity is attributed to the synergy of FGS and Pt nanoparticles on the electrocatalytic activity to H2O2. The glucose biosensor has good responses because of the large surface area and fast electron transfer of graphene and Pt nanoparticles. The biosensor also has good reproducibility and long-term stability.

Acknowledgements

This work was supported by a laboratory-directed research and development program at Pacific Northwest National Laboratory (PNNL). The work was performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy (DOE) and located at PNNL. PNNL is operated by Battelle for DOE under Contract DE-AC05-76RL01830. Ilhan A. Aksay acknowledges support from Army Research Office (ARO)/Multidisciplinary Research Initiative (MURI)

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