A surface plasmon resonance (SPR) sensor for detection of toluene (C6H5CH3)

Abstract

Herein, we report a novel surface plasmon resonance (SPR) sensor modified with toluene binding domain (TBD) to detect toluene. The toluene binding domain was manipulated with cysteines for rapid, easy and orientation-controlled immobilization of the protein onto a SPR gold surface due to the specific interaction between a 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 the cross-sectional analysis by atomic force microscopy (AFM). The SPR analysis of cysteine-tagged TBD adsorption showed that cysteine-tagged TBD bound onto a gold thin film with high binding affinity. With a SPR-based ligand binding assay, a detectable increase in the SPR response was observed with 15.62 uM of toluene. Due to the inherent specificity of TBD, this method showed a comparative specificity for the determination of toluene, as it exhibited no SPR response to aromatic compounds such as p-xylene and benzene. Taken together, the results obtained from this study indicate that TBD-modified SPR sensor system can be useful for detecting toluene, a volatile organic compound widely distributed in the environment.