Uptake and Depuration Kinetics of Pacific Ciguatoxins in Orange-Spotted Grouper (Epinephelus coioides).

Ciguatoxins (CTXs), produced by toxic benthic dinoflagellates, can bioaccumulate in marine organisms at higher trophic levels. The current study evaluated the uptake and depuration kinetics of some of the most potent CTXs, Pacific CTX-1, -2, and -3 (P-CTX-1, -2, and -3), in orange-spotted grouper (Epinephelus coioides) exposed to 1 ng P-CTXs g-1 fish daily. Over a 30 d exposure, P-CTX-1, -2, and -3 were consistently detected in various tissues of exposed fish, and the concentrations of the total P-CTXs in tissues generally ranked following the order of liver, intestine, gill, skin, brain, and muscle. Relatively higher uptake rates of P-CTX-1 in the groupers were observed compared with those of P-CTX-2 and -3. The depuration rate constants of P-CTX-1, -2, and -3 in different tissues were (0.996-16.5) × 10-2, (1.51-16.1) × 10-2, and (0.557-10.6) × 10-2 d-1, respectively. The accumulation efficiencies of P-CTX-1, -2, and -3 in whole groupers were 6.13%, 2.61%, and 1.15%, respectively. The increasing proportion of P-CTX-1 and the decreasing proportion of P-CTX-2 and -3 over the exposure phase suggest a likely biotransformation of P-CTX-2 and -3 to P-CTX-1, leading to higher levels of P-CTX-1 in fish and possibly a higher risk of CTXs in long-term exposed fish.

Development of a signal-enhanced LFIA based on tyramine-induced AuNPs aggregation for sensitive detection of danofloxacin.

A signal-enhanced LFIA based on tyramine (TYR)-induced AuNPs aggregation has been developed for the sensitive detection of danofloxacin (DAN). In the model, the hydroxyl radical produced by HRP catalyzing H2O2 can trigger the TYR-AuNPs to aggregate on the T or C line for enhancing the detection signal. The linear range of TYR-AuNPs LFIA was 0.25-5 ng mL-1 with the limit of detection (LOD) of 0.032 ng mL-1, and the LOD was 8-fold lower than that of the traditional AuNPs LFIA (0.26 ng mL-1). The TYR-AuNPs LFIA could be used with the naked eyes to qualitatively detect DAN with a cut-off limit of 2.5 ng mL-1, which was 4-fold lower than that of the traditional AuNPs LFIA (10 ng mL-1). The recoveries of TYR-AuNPs LFIA were 86.04-105.14% and 92.41-110.19%, with the coefficient of variation of 1.71-2.05% and 4.42-5.89% in chicken and pork, respectively.