Effects of Methoxyfenozide-Loaded Fluorescent Mesoporous Silica Nanoparticles on (L.) (Lepidoptera: Plutellidae) Mortality and Detoxification Enzyme Levels Activities.

The diamond back moth, , causes severe damage at all crop stages, beside its rising resistance to all insecticides. The objective of this study was to look for a new control strategy such as application of insecticide-loaded carbon dot-embedded fluorescent mesoporous silica nanoparticles (FL-SiO NPs). Two different-sized methoxyfenozide-loaded nanoparticles (Me@FL-SiO NPs-70 nm, Me@FL-SiO NPs-150 nm) were prepared, with loading content 15% and 16%. Methoxyfenozide was released constantly from Me@FL-SiO NPs only at specific optimum pH 7.5. The release of methoxyfenozide from Me@FL-SiO NPs was not observed other than this optimum pH, and therefore, we checked and controlled a single release condition to look out for the different particle sizes of insecticide-loaded NPs. This pH-responsive release pattern can find potential application in sustainable plant protection. Moreover, the lethal concentration of the LC value was 24 mg/L for methoxyfenozide (TC), 14 mg/L for Me@FL-SiO NPs-70 nm, and 15 mg/L for Me@FL-SiO NPs-150 nm after 72 h exposure, respectively. After calculating the LC, the results predicted that Me@FL-SiO NPs-70 nm and Me@FL-SiO NPs-150 nm exhibited better insecticidal activity against than methoxyfenozide under the same concentrations of active ingredient applied. Moreover, the activities of detoxification enzymes of were suppressed by treatment with insecticide-loaded NPs, which showed that NPs could also be involved in reduction of enzymes. Furthermore, the entering of FL-SiO NPs into the midgut of was confirmed by confocal laser scanning microscope (CLSM). For comparison, under treatment with water as control was also observed under CLSM. The control exhibited no fluorescent signal, while the larvae treated with FL-SiO NPs showed strong fluorescence under a laser excitation wavelength of 448 nm. The reduced enzyme activities as well as higher cuticular penetration in insects indicate that the nano-based delivery system of insecticide could be potentially applied in insecticide resistance management.