Photo-responsive shell cross-linked micelles based on carboxymethyl chitosan and their application in controlled release of pesticide

An amphiphilic carboxymethyl chitosan conjugate with photolabile 2-nitrobenzyl side groups (NBS-CMCS) was synthesized, which could self-assemble into polymeric micelles in aqueous condition following by adding dropwise dialdehyde to form a cross-linking structure. TEM and (1)H NMR confirmed that the cross-linked micelles had a core-shell configuration with an average diameter of 140 ± 5.5 nm. DLS and TEM observations showed that the cross-linked micelles were stable in aqueous solution at pH 7.0 without light irradiation, while they could transfer into nanocapsules upon exposure to 365 nm UV light. Diuron, a photosynthetic inhibitor, was encapsulated in the cross-linked micelles reaching encapsulation efficiency as much as 91.9%. No release of the encapsulated diuron was detected without light, whereas a release rate as high as 96.8% over 8h at pH 7.0 buffer was observed under solar stimulated irradiation, indicating that the cross-linked micelles may be used as a photo-controlled sustained release carrier for the delivery of photosynthetic inhibitor.