Tetrodotoxin

32171958

A fluorescence aptasensor for the highly specific and sensitive determination of tetrodotoxin was established with tetrodotoxin-aptamer as the recognition unit, berberine as the signal reporter and exonuclease I as the elimination agent for the background. Berberine has a weak fluorescence emission at 540 nm, and it can form the tetrodotoxin-aptamer/berberine complex, resulted in an increased fluorescence. After introducing exonuclease I, it can degrade the single strand oligonucleotides of tetrodotoxin-aptamer into the single nucleotide in the absence of tetrodotoxin, which lead to dramatic fluorescence quenching, and reduce the background signal of sensing system. Once tetrodotoxin is in the presence, tetrodotoxin-aptamer is converted into the stable neck ring conformation, which resists the degradation of exonuclease I and provides a more rigid micro-environment for the excited state of berberine, and then the strong fluorescence is observed. Based on the above properties, an ultrasensitive label-free fluorescence aptasensor for tetrodotoxin is established. The fluorescence aptasensor shows good analytical performance with the linear increase of fluorescence intensity at the tetrodotoxin concentration from 0.030 nM to 6.0 × 103 nM. The detection limit of 11.0 pM is much lower than that of other reported sensor methods.

Exonuclease I; Fluorescence aptasensor; Label-free; Tetrodotoxin.

Exonuclease I-assisted fluorescence aptasensor for tetrodotoxin

Yifeng Lan 1, Guojie Qin 2, Yanli Wei 3, Li Wang 4, Chuan Dong 1

2020 May;

32088461

Tetrodotoxin (TTX), a potent neurotoxin, is found in various phylogenetically diverse taxa. In marine environments, the pufferfish is at the top of the food chain among TTX-bearing organisms. The accumulation of TTX in the body of pufferfish appears to be of the food web that begins with bacteria. It is known that toxic pufferfishes possess TTX from the larval/juvenile stage. However, the source of the TTX is unknown because the maternally sourced TTX is extremely small in quantity. Therefore, the TTX has to be obtained from other organisms or directly from the environment. Here, we report evidence that the source of TTX for toxic fish juveniles including the pufferfish (Chelonodon patoca) and the goby (Yongeichthys criniger) is in the food organisms, as seen in their gut contents. Next generation sequencing analysis for the mitochondrial COI gene showed that the majority of the sequence recovered from intestinal contents of these toxic fishes belonged to the flatworm Planocera multitentaculata, a polyclad flatworm containing highly concentrated TTX from the larval stage. PCR specific to P. multitentaculata also showed that DNA encoding the planocerid COI gene was strongly detected in the intestinal contents of the goby and pufferfish juveniles. Additionally, the planocerid specific COI sequence was detected in the environmental seawater collected from the water around the sampling locations for TTX-bearing fish. These results suggest that planocerid larvae are the major TTX supplier for juveniles of TTX-bearing fish species.

Marine toxin; Pufferfish toxin; Tetrodotoxin (TTX); Toxification process; Toxin accumulation.

The planocerid flatworm is a main supplier of toxin to tetrodotoxin-bearing fish juveniles

Shiro Itoi 1, Tatsunori Sato 2, Mitsuki Takei 2, Riko Yamada 2, Ryuya Ogata 2, Hikaru Oyama 2, Shun Teranishi 2, Ayano Kishiki 2, Takenori Wada 2, Kaede Noguchi 2, Misato Abe 2, Taiki Okabe 2, Hiroyuki Akagi 2, Maho Kashitani 2, Rei Suo 2, Tomoko Koito 2, Tomohiro Takatani 3, Osamu Arakawa 3, Haruo Sugita 2

2020 Jun