A Surface Plasmon Resonance Sensor for Detection of Toluene (C6H5CH3)

Herein, we report a novel surface plasmon resonance (SPR) sensor modified with a toluene-binding domain (TBD) to detect toluene. The TBD was manipulated with cysteines for rapid, easy, and orientation-controlled immobilization of the protein onto an SPR gold surface, due to the specific interaction between bare gold and the thiol group (-SH) of cysteines. After the purification and on-chip immobilization of the recombinant TBD, the thickness of cysteine-tagged TBD was determined to be approximately 1.8 nm according to atomic force microscopic cross-sectional analysis. The SPR analysis of cysteine-tagged TBD adsorption showed that cysteine-tagged TBD binds to gold thin film with high binding affinity. With an SPR-based ligand binding assay, a detectable increase in the SPR response was observed for 15.62 mu M of toluene. Owing to the inherent specificity of the TBD, this method showed comparative specificity for the determination of toluene, as it exhibited no SPR response to aromatic compounds such as p-xylene or benzene. Taken together, the results obtained from this study indicate that a TBD-modified SPR sensor system can be useful for detecting toluene, a volatile organic compound widely distributed in the environment.