Tailoring layered double hydroxides into pH- and protease-responsive slow-release pesticide: Insecticidal activity, photostability, and environmental friendliness

Abstract

Two controlled-release pesticide systems based on layered double hydroxides (i.e. PDA/LDH@DNF and Zein/LDH@DNF) were developed to improve the anti-photodegradation and controlled release of dinotefuran (DNF) using polydopamine (PDA) or zein as the outer layer and layered double hydroxides (LDHs) as the inner carrier. Results showed that DNF was loaded into the LDHs surface by hydrogen bonding and electrostatic attraction, while both PDA and zein molecules were coated on the outer surface of LDH@DNF through hydrogen bonding. The loading proportions of PDA/LDH@DNF and Zein/LDH@DNF were as high as 10.17 % and 11.85 %, respectively. The PDA/LDH@DNF performed a pH-responsive release behavior due to the dissolution of carriers under different pH conditions. The cumulative amount of released DNF within 24 h at pH 5, 7, and 9 was 84.86 %, 59.59 %, and 33.44 %, respectively. On the other hand, Zein/LDH@DNF showed enzyme-responsive slow-release behavior. The final cumulative release of DNF from Zein/LDH@DNF in the presence of protease reached 46.77 % contrasting that of 24.69 % without adding protease. The anti-photodegradation capacities of DNF in PDA/LDH@DNF and Zein/LDH@DNF were improved to nearly 2.5 times higher than that of DNF without protection under ultraviolet irradiation. Compared with the commercial dinotefuran granules, the prepared systems enhanced the immobilization of DNF by reducing pesticide leaching by 54.55–64.72 % in soil. The two controlled-release pesticide systems were environmental-friendly to non-targeted zebra fish according to biosafety evaluation. Consequently, this research provides a controlled and sustained technology for long-term pest management and thus enhance pesticide efficiency as well as decline contamination to environment.