Photoresponsive Vesicles of Pendimethalin, γ-Cyclodextrin, and an Azobenzene for Controlled Release of a Pesticide

Abstract

Traditional pesticide emulsion formulation may exert deleterious effects on the environment and even induce stress on nontarget crops in the vicinity. In this study, γ-cyclodextrin (γ-CD)-encapsulated azobenzene derivative nanovesicles were synthesized and loaded with pendimethalin to obtain pendimethalin-loaded γ-CD/azobenzene derivative nanovesicles. Upon exposure to ultraviolet irradiation or sunlight, the azobenzene derivatives are converted from the trans- to cis- configuration, leading to the dissociation of the ternary host–guest complexes, resulting in the vesicle rupture and the subsequent release of pendimethalin. Further investigations were conducted on the γ-CD/azobenzene nanovesicles. According to the release characteristics of herbicides, the release rate of pendimethalin under ultraviolet light (365 nm) or sunlight conditions reached 88.3 ± 3%, which was 4.3 times higher than that under dark conditions, demonstrating excellent photocontrolled release behavior. Pot experiments showed that the herbicidal activity of pendimethalin-loaded nanovesicles against Portulaca oleracea (L.) and Echinochloa crusgalli (L.) Beauv. at the recommended dose was comparable to that of the pendimethalin technical under illuminated conditions. Furthermore, genotoxicity experiments reveal a notable increase in the mitotic index of onion root tip cells treated with pendimethalin-loaded nanovesicles, indicating that it had minimal inhibitory effect on cell metabolism and the genotoxicity was lower than that of pendimethalin technical. Pendimethalin-loaded nanovesicles exhibited favorable stability and photoresponsive performance. These findings reveal a promising avenue for responsive material design and release modulation using such nanovesicle systems, providing insights into their potential applications in targeted pesticide delivery systems.