Elsevier

Biosensors and Bioelectronics

Volume 23, Issue 7, 28 February 2008, Pages 1180-1184
Biosensors and Bioelectronics

Short communication
Enhanced resonance light scattering based on biocatalytic growth of gold nanoparticles for biosensors design

https://doi.org/10.1016/j.bios.2007.10.024Get rights and content

Abstract

The biocatalytic growth of gold nanoparticles (Au-NPs) has been employed in the design of new optical biosensors based on the enhanced resonance light scattering (RLS) signals. Both absorption spectroscopy and transmission electron microscopy (TEM) analysis revealed Au-NP seeds could be effectively enlarged upon the reaction with H2O2, an important metabolite that could be generated by many biocatalytic reactions. Upon the stepwise enlargement of Au-NPs, the light scattering intensity could be greatly enhanced, which then allowed the quantitative detection of the analyte, H2O2. Further combination of the biocatalytic reaction that can yield H2O2 by using the enzyme, glucose oxidase, with the enlargement of Au-NPs enabled the design of a sensitive glucose biosensor using the RLS technique. In the present study, we could achieve the detection of glucose in a linear range of 1.0 × 10−6 M to 1.1 × 10−4 M, with detection limit of 6.8 × 10−7 M.

Introduction

Nanomaterials have attracted widespread attention since the 1990s because of their specific features that differ from bulk materials. The application of nanomaterials to the design of biosensors is nowadays one of the most active research fields because of their high activity, good selectivity, and tremendous specific surfaces (Shi et al., 2004). Among the various nanomaterials, metal nanoparticles are of particular interests, and have attracted significant attention in the fields of biosensing (Penn et al., 2003). Many detection methods have been developed based on their fascinating electronic and optical properties, such as colorimetric method for specific DNA sequence detection (Storhoff et al., 1998), fluorescence method for protein assays (Hsieh et al., 2007), electrochemical method for glucose sensing (Wu et al., 2007), and so on.

Recently, with the distinct advantages of simplicity, rapidness and high sensitivity, resonance light scattering (RLS) technique was developed to study the extended aggregates of chromophores or bio-assemblies (Huang et al., 2003, Kano et al., 2000). For the analytical purpose, RLS technique has been proposed for the determination of DNA (Bao et al., 2002, Zou et al., 2007), proteins (Zhong et al., 2004), metal ions (Liu et al., 2000), drugs (Feng et al., 2001), and so on. In particular, with the rapid development of nanotechnology, great attention has been focused on the use of metal nanoparticles as the RLS probes (Du et al., 2006, Li et al., 2006, Liu et al., 2006, Wang et al., 2007, Wu et al., 2006a), which was mainly based on their extremely strong light scattering at the plasmon-resonance wavelength due to the collective oscillation of their conduction electrons. For example, Li's et al. reported a highly sensitive light scattering assay for DNA hybridization in a homogeneous solution by using gold nanoparticles (Au-NPs) as the label of oligo-nucleotide probes (Du et al., 2006). Recently, based on the formation of silver nanoparticles, Huang et al. developed a simple light scattering method to detect the Sudan dyes in food products (Wu et al., 2006a). Also, based on the extremely strong RLS of Au-NPs, Ren and co-workers developed a single-molecule detection technique, namely RLS correlation spectroscopy, and successfully achieved the rapid detection of DNA sequences (Wang et al., 2007).

In this paper, we report a new design mode of RLS biosensors based on the biocatalytic growth of Au-NPs. The use of biomaterials as active components for the growth of nanoparticles is actually a new and emerging area in nanobiotechnology (Willner et al., 2006). Since the growth of NPs dominates their chemical properties, the biocatalytic reactions that yield the NPs then allow the design of different biosensors based on the change of the optical or electronic properties of Au-NPs. Only recently, the biocatalytic growth of Au-NPs was employed in several analytical protocols, such as absorption spectroscopy (Xiao et al., 2004, Zayats et al., 2005), surface plasmon resonance (Yang et al., 2007), and electrochemical detection (Zhou et al., 2006). Within our knowledge, no study has been reported to introduce this biocatalytic growth of Au-NPs for the RLS biosensors design. Therefore, we report here on the application of this process to develop a new assay protocol based on the enhanced RLS signals of biocatalyst-enlarged Au-NPs. The present assay is conceptually different from the previous RLS assays utilizing metal nanoparticles, as they either rely on determining the amount of metal nanoparticles (Wu et al., 2006a), or rely on large ensembles of nanoparticles (Du et al., 2006, Li et al., 2006, Liu et al., 2006, Wang et al., 2007).

As an example, we report in this work on the catalytic growth of Au-NPs by H2O2, an important metabolite of organisms, and the further application of the process to develop a glucose biosensor upon the integration of enzyme (glucose oxidase) with the Au-NPs enlargement using RLS technique. The work described here not only presents a new RLS biosensor design mode, but also provides an alternative approach to detect numerous substrates by using their corresponding oxidases.

Section snippets

Materials

The glucose oxidase (E.C. 1.1.3.4) was obtained from Sigma Chemical Co. Cetyltrimethylammonium chloride (CTAC) was purchased from Nanjing Robiot Co. (China). Hydrogen tetrachloroaurate (HAuCl4·3H2O), trisodium citrate, and glucose were purchased from Beijing Chemical Co. (China). The stock solution of glucose was allowed to incubate at room temperature overnight before use. The stock solution of H2O2 was freshly diluted from 30% solution. All other reagents were of analytical reagent grade, and

Results and discussion

We first performed experiments by employing the growth solution containing H2O2. Fig. 1 shows the typical TEM images of Au-NP seeds (A) and the enlarged NPs upon the reaction with H2O2 (B). As can be seen, the as-prepared Au-NP seeds were nearly of the same size with spherical shapes. The average diameters measured from TEM image data were calculated to be 14 ± 1 nm. Upon the reaction with H2O2 (1.2 × 10−4 M), the size of Au-NPs was observed to be obviously enlarged, about 32 nm, although not very

Conclusions

In conclusion, the present study has demonstrated the development of a new type of RLS biosensors which is based on the biocatalytic enlargement of Au-NPs. The effective enlargement of Au-NPs upon the reaction with H2O2, results in enhanced RLS signals, which then enables the design of a sensitive biosensor using RLS technique. Furthermore, by combining the catalytic reaction of the substrate by the corresponding enzyme, for example, glucose oxidase, with the enlargement of Au-NPs, a sensitive

Acknowledgement

This work was supported by the National Natural Science Foundation of China (Nos. 20427003 and 20575064).

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