NIR laser-activated polydopamine-coated Fe3O4 nanoparticles used as a novel precise photothermal insecticide

Chemical pesticides are widely used in prevention and control of pests. However, low insecticidal efficacy, high environmental risks and pesticidal resistance severely constrain further applications. In this study, a near-infrared (NIR) laser-activated pesticide-free Fe3O4@PDA nanoplatform with a low production cost was constructed for precise photothermal killing of housefly larvae. The polydopamine (PDA) surface-functionalized Fe3O4 nanoparticles (Fe3O4@PDA NPs) were synthesized by simply mixing dopamine with Fe3O4 NPs under aerobic alkaline conditions. These Fe3O4@PDA NPs exhibited superb photothermal performance with near-infrared (NIR) laser irradiation. Larval uptake results revealed greater in vivo uptake of Fe3O4@PDA NPs than bare Fe3O4 NPs when housefly larvae were fed a NP-treated diet. These NPs exhibited favorable biocompatibility and showed no obvious influence on larval development and intestinal microbial population. However, when irradiated with a NIR laser, the NPs efficiently induced death of housefly larvae with high temperature (Tmax > 50 ℃) damage to the intestinal wall and subsequent leakage of intestinal bacteria into the hemocoel. Furthermore, uneaten NPs can be collected by magnetic absorption and show excellent thermal stability, which allowed recycling of these environmentally friendly nanoparticles. The Fe3O4-based nanoparticles described in the present study integrate the independence of pesticides, pronounced photothermal control of pests, and environmental friendliness, making this nanoplatform promising for controlling vector pests and diseases.