Development of an ultra high sensitive tissue biosensor for determination of swellfish poisoning, tetrodotoxin.

A simple tissue biosensor for measuring Na+ channel blockers such as tetrodotoxin (TTX) and saxitoxin (STX) has been developed. The membrane of frog bladder has Na+ channels which control the passage of Na+. It is well known that TTX blocks Na+ channels. The tissue biosensor consists of a Na+ electrode integrated within a flow cell. The tip of the electrode was covered with frog bladder membrane sandwiched between two sheets of cellulose acetate membrane, and the electrode was set in a flow cell. A solution of 8% NaCl was carried in the cell and the output of the electrode allowed to stabilize. TTX was injected into the sensor system and measured from the inhibition ratio of the sensor peak output. One assay took approximately 5 min. The lower limit of detection was 86 fg. The continuous determination of TTX was feasible for 250 h in the presence of 0.003% NaN3. A Linear correlation was obtained between TTX activities of F-niphobles and F-parudale determined by the methods of TTX sensor and mouse assay.