Development of fluorometric detection for saxitoxin with its specific binding peptide

Abstract

Saxitoxin (STX) is a representative neurotoxin among paralytic shellfish poisons and poses a serious threat to human health. When ingested, it blocks sodium permeability of excitatory membranes and causes neuromuscular paralysis and respiratory arrest, leading to death. Therefore, technology capable of detecting STX in advance is required. In this study, to develop the bioreceptor that specifically binds to STX, a phage display was introduced. For this technique, the STX hapten was synthesized by reacting the amine group of STX with the carboxyl group of ovalbumin, a carrier protein, using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysulfosuccinimide sodium salt coupling reaction. The peptides discovered through this were selected according to frequency and similarity, and the 5′-terminal was modified with 5-carboxyfluorescein as the fluorophore. To construct a simple verification procedure for the discovered peptides, we developed a peptide-based fluorometric sensor using the graphene oxide (GO) quenching phenomenon. In this sensor, GO as a quencher can be strongly adsorbed through π–π interaction with a fluorophore and charge–charge interaction with STX at pH 7.4, and it showed a low detection limit of 1.5 ppb.