Mechanism study of the molluscicide candidate PBQ on Pomacea canaliculata using a viscosity-sensitive fluorescent probe

PBQ [1-(4-chlorophenyl)-3-(pyridin-3-yl) urea], an enormous potent molluscicide, showed excellent Pomacea canaliculata control activity and low toxicity for other aquatic organisms, but its snail-killing mechanisms are still not fully understood. We employed an optical method to elucidate PBQ action via a novel fluorescent viscosity probe, NCV. As the viscosity in the test solutions increased, compared with that in pure ethanol, a 54-fold fluorescence intensity enhancement of NCV was observed in 310 cP of 90% glycerol. Furthermore, NCV successfully exhibited a selective fluorescence response towards monensin-induced cellular viscosity changes in HepG2 cells. The liver, stomach, and foot plantar of the tested snails were frozen and sectioned for fluorescent imaging experiments after the treatment with different PBQ concentrations over various times. A significant fluorescent increase in the snail's liver was observed upon exposure to 0.75 mg/L PBQ for 72 h, which highlighted an increase in viscosity. Hematoxylin and eosin (HE) staining further supported PBQ-induced liver damage with a viscosity increase in P. canaliculata. Our study provides a new rapid optical visualization method to study the killing mechanisms of PBQ and may help discover new chemicals that control snail populations.