Comparison of two glutathione S-transferases used in capacitive biosensors for detection of heavy metals

Abstract

This work describes the development of a heavy-metal biosensor based on either recombinant 6His-Tag glutathione S-transferase (GST-(His)₆) or glutathione S-transferase Theta 2-2 (GST-theta 2-2), and a capacitive transducer. The dynamic range of the pure bovine liver GST-Theta 2-2 biosensor was 1 fM to 1 mM for Zn²⁺, and 10 pM to 1 mM for Cd²⁺. The GST-(His)₆ biosensor was able to detect Zn²⁺ and Cd²⁺ in the range of 1 fM to 10 µM, and Hg²⁺ in the range of 1 fM to 10 mM. The bovine liver GST Theta 2-2 biosensor displays an increased selectivity and a wider dynamic range for Zn²⁺ compared with the GST-(His)₆ biosensor. Therefore, by using different GST isozymes, it is possible to modulate important characteristics of capacitive biosensors for the detection of heavy metals.

Keywords:

• Capacitive biosensor
• 6His-tag glutathione S-transferase
• Bovine liver glutathione S-tranferase theta 2-2
• Heavy-metal detection

Acknowledgements

The authors give thanks to the following organizations for financial support: (SPO) T.R. Primary Ministry State Planning Organization, project no. DPT-05-09; (BAP) Middle East Technical University, Human Resources Development in Education Programme, project no. BAP-08-11-DPT2002K120510. Also, thanks to Dr Belgin İşgör, Department of Materials Engineering, Atılım University, Ankara, Turkey, for supplying the purified bovine liver GST-Theta 2-2.