The development of highly selective and sensitive surface plasmon resonance (SPR) immunoassay for the rapid detection of illegal compound using secondary antibody interaction labelled nanoparticle was conducted. For the construction of SPR sensor surface, the illegal compound (clenbuterol) was immobilized as antigen onto gold succinimide-terminated monolayer to perform amide-coupling reaction. In order to avoid non-specific reaction, the blocking agent (ethanol amine) was injected to the SPR system. Furthermore, indirect competitive inhibition method was employed in the detection of clenbuterol. In this work, the antibody solution (PBS solution containing clenbuterol antibody) premixed with a sample solution (PBS solution containing antigen) before the injection into the sensing system. As the premixed solution flowed over the sensor surface, the SPR senses the dielectric constant change at the interface due to the binding of the unreacted primary antibody to antigen-immobilized on the sensor surface. After this primary antibody detection, secondary antibody was injected to the SPR sensor surface. Here, we compared the signal difference of secondary antibody injection labelled Au nanoparticles (d = 40 nm). For the regeneration of the sensor surface, 0.1 M NaOH was used, so primary and secondary antibodies could be detached from the sensor surface. According to the indirect competitive inhibition method, it was found that the sensitivity for clenbuterol detection was enhanced from 2.5 ppt to 0.07 ppt.
Distance-regulating surface plasmon catalyzed coupling reaction of p-nitrophenyl disulfide