Quantitative detection of tetrodotoxin (TTX) by a surface plasmon resonance (SPR) sensor

We report the quantitative antibody-based detection of a low-molecular weight molecule tetrodotoxin (TTX) (∼319 Da) by inhibition assay with a surface plasmon resonance (SPR) sensor. A novel anti-TTX antibody sensing surface was developed by chemically immobilizing TTX on a gold film with a mixed self assembled monolayer (SAM) consisting of amine terminated oligo-ethylene glycol (OEG) alkanethiol and a hydroxyl terminated OEG alkanethiol. The ratio of amine to hydroxyl terminated OEG alkanethiols and TTX immobilization chemistry were optimized to maximize specific anti-TTX binding, while minimizing non-specific binding. The calibration curves are reported for two antibody concentrations incubated with samples of varying TTX concentrations ranging from 0.01 to 10,000 ng/mL. The detection limit for TTX is defined as IC20 (20% inhibitory concentration), which is ∼0.3 ng/mL in this work. The corresponding calibration curve has a characteristic IC50 (50% inhibitory concentration) of ∼6 ng/mL. The ability to reproducibly regenerate the TTX-immobilized surface was also demonstrated.