Development of controlled release formulations of azadirachtin-A employing poly(ethylene glycol) based amphiphilic copolymers

Abstract

Controlled release (CR) formulations of azadirachtin-A, a bioactive constituent derived from the seed of Azadirachta indica A. Juss (Meliaceae), have been prepared using commercially available polyvinyl chloride, polyethylene glycol (PEG) and laboratory synthesized poly ethylene glycol-based amphiphilic copolymers. Copolymers of polyethylene glycol and various dimethyl esters, which self assemble into nano micellar aggregates in aqueous media, have been synthesized. The kinetics of azadirachtin-A, release in water from the different formulations was studied. Release from the commercial polyethylene glycol (PEG) formulation was faster than the other CR formulations. The rate of release of encapsulated azadirachtin-A from nano micellar aggregates is reduced by increasing the molecular weight of PEG. The diffusion exponent (n value) of azadirachtin-A, in water ranged from 0.47 to 1.18 in the tested formulations. The release was diffusion controlled with a half release time (t(1/2)) of 3.05 to 42.80 days in water from different matrices. The results suggest that depending upon the polymer matrix used, the application rate of azadirachtin-A can be optimized to achieve insect control at the desired level and period.

Azadirachtin downregulates the expression of the CREB gene and protein in the brain and directly or indirectly affects the cognitive behavior of the Spodoptera litura fourth‐instar larvae

“…Azadirachtin is a botanical pesticide used to control lepidopteran pests. Because of its high efficiency and low toxicity 7,8 it can be used as a substitute or in rotation with current synthetic insecticides in integrated pest management programs 44,45 . This is mainly because azadirachtin is a good anti‐feedant 46 .…”

“…Azadirachtin, an insecticidal active component of Azadirachta indica , has attracted considerable attention both locally and internationally 5,6 . However, it is a broad‐spectrum compound exhibiting a potentially low level of selectivity to non‐targeted arthropods, including some pollinator species 7,8 . Azadirachtin can also interfere with the central nervous system (CNS) by inhibiting excitatory cholinergic transmission and partly blocking the calcium channel 9 .…”

“…5,6 However, it is a broad-spectrum compound exhibiting a potentially low level of selectivity to non-targeted arthropods, including some pollinator species. 7,8 Azadirachtin can also interfere with the central nervous system (CNS) by inhibiting excitatory cholinergic transmission and partly blocking the calcium channel. 9 Previous research has shown that different clusters of dopaminergic neurons respond differently to azadirachtin, 10 which can induce aversive taste memory in Drosophila and bee, [11][12][13] and such memory is typically regulated by the dopaminergic signals in the brain.…”

Stability Phenomena Associated with the Development of Polymer-Based Nanopesticides

“…In general, the release of pesticides from polymer-based nanocapsules occurs by diffusion of the active compound in the nucleus through the polymeric membrane until it reaches the surface [ 34 ]. Multiple factors can interfere with the release mechanisms of nanocapsules, and it has been reported that the release rates of the active principle are directly proportional to the molecular weight of the polymer [ 16 , 54 ]. In addition, polymer's mechanical properties, the degree of biodegradability, the thickness of the coating, and other factors such as the physiology and the water or cations content in the soil significantly affect the mechanism of active principle release [ 33 , 45 , 50 ].…”

Enhanced acaricidal activity of ricinine achieved by the construction of nano-formulation using amphiphilic block copolymer

“…Amphiphilic copolymers have been widely applied in drug delivery systems, 19 and recently are also focused as a carrier for the delivery of pesticides. 20,21 Such polymer can form aggregates with various microstructures, e.g. micelle, vesicle and nanoparticle, which involve hydrophobic microdomains that are capable to entrap water insoluble stuffs including the hydrophobic pesticides.…”