Biosensors based on electrochemistry are now attracting considerable attention as potential successors to a wide range of analytical techniques due to their unique properties of specificity [1
]. The key aspect of an electrochemical biosensor is the generation or modulation of electrical current in an electronic circuit between the bio-reaction or bio-recognition systems and the electronic elements. The high demand for selection and sensation requires not only the appropriate biological macromolecules with high active, but also the suitable substrates with biocompatible surroundings and efficient transport of electrons, but it is difficult for conventional electrodes to satisfy the demands. To that end, specific materials and structures with novel biocompatibility, stability, and electron transport property are demanded, for example, the intensively investigated nanomaterials [4
Nanomaterials, especially the one-dimensional nanostructures such as carbon nanotubes (CNT) [6
] and metal [7
], semiconductor [8
], or conducting polymer [9
] nanowires or nanotubes, are particularly attractive for biosensor application due to their unique advantages including high surface-to-volume ratio, elevated electrochemical activity, and eminent electron communication features. Usually, nanotubes and nanowires are incorporated into the functional systems by a variety of methods, such as solution evaporation [10
], sol–gel encapsulation [11
], and polymer-assisted dispersion [12
]. These methods generally result in disarrayed and layered films with the absorbed catalytic enzyme sites partially blocked and the substrate transport to the enzymes hindered [13
], leading to a low amperometric responses upon bio-electrocatalysed oxidation or reduction of the analyte. To overcome this problem, perpendicularly aligned nanotube or nanowire arrays can be formed as sensing devices [7
], which will lead to an increment of enzyme content associated with the electrode surface, an improvement of electrical communication between the redox center and the electrode, and thus an enhancement of the transduced amperometric signal.
Metal gold is one of the mostly used noble metals in biosensors; several reports have demonstrated that gold nanoparticles may be used as a hopping bridge of electrons generated from the enzyme catalytic redox reaction [16
]. Besides facilitating the transfer of electrons, gold nanoparticles can also provide a biocompatible environment for proteins, since they are not toxic to the biological systems [19
]. Gold nanoparticles are an excellent candidate for replacing potentially harmful mediators in the construction of biosensors.
In this paper, we fabricated the gold nanoelectrode array (NEA) in the template of polycarbonate (PC) membranes. Free standing nanostructured gold nanowire arrays were obtained by direct electrodepositing on the conventional gold electrode, analogous to ultramicroelectrode ensembles reported by Penner et al. [21
]. The whole system can be considered as a modified electrode consisting of millions of nanowires which contact well with the substrate electrode; the diameter of each nanowire is about 450 nm and the length is even 4 μm. The 3D nanowire array results in large electroactive surface area, which is about five times as large as the conventional gold electrode. The high electroactive surface can not only enhance the sensitivity to hydrogen peroxide, but also provide large space for the loading of the enzymes. Considering the advantages of NEA and biocompatibility of metal gold, we put the gold NEA into the use of enzymes biosensors, which showed high sensitivity and wide linear range.