A biological method for the quantitative measurement of tetrodotoxin (TTX): tissue culture bioassay in combination with a water-soluble tetrazolium salt.

A tissue culture bioassay, using the mouse neuroblastoma cell line (Neuro2A), was improved to provide a simple and sensitive bioassay for TTX or sodium channel-blocking toxins (SCB). The water-soluble tetrazolium salt, 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetraz olium, monosodium salt (WST-1), was applied to replace the time-consuming and subjective cell-counting procedure of the cells with automatic measurement, using a microplate reader. It was also confirmed that this method is directly applicable to bacterial culture supernatants, with the precaution of possible interference.