Construction and characterization of a temperature-responsive nanocarrier for imidacloprid based on mesoporous silica nanoparticles.

Nanopesticides have great potential applications due to their stability enhancement, sustained release and target affinity. In this work, a temperature-responsive nanocarrier for imidacloprid (IMI) was constructed using mesoporous silica nanoparticles (MSNs) as the core and paraffin wax (PW) as the outer layer. IMI was loaded into MSNs by screening the drug/carrier mass ratios to obtain the optimized IMI/MSNs formulation with a high drug loading (27.47 %). IMI/MSNs were functionalized with octadecyltrimethoxysilane (C18TMS) and further coated with a temperature-responsive trigger (PW) through hydrophobic interactions. Thus, a temperature-responsive nanocarrier for IMI (PW/IMI/MSNs) was constructed. Fourier transforms infrared (FT-IR), thermogravimetric analysis (TGA) and N2 adsorption-desorption isotherm measurements confirmed the successful loading of IMI into MSNs and the coating of PW on the surface of the IMI/MSNs. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses indicated that PW/IMI/MSNs with diameters approximately 100 nm had an ordered hexagonal mesoporous structure with a surface coating of approximately 6 nm. In addition, an in vitro release experiment showed that PW/IMI/MSNs displayed a temperature-responsive sustained release property. Correspondingly, the bioactivity assay of the PW/IMI/MSNs showed that the insecticidal activity greatly increased with temperature. This formulation is expected to have potential applications in some high-temperature areas, such as Turpan in Xinjiang Province, for improving the utilization efficiency of IMI.