Chitosan oligosaccharide copolymer micelles with double disulphide linkage in the backbone associated by H-bonding duplexes for targeted intracellular drug delivery

A folic acid (FA) conjugated chitosan oligosaccharide (CSO) polylactic acid (PLA) copolymer FA-CSO-PLA with double disulphide linkage in the backbone directed by H-bonding association duplex was synthesized, and its self-assembled micelles were evaluated as smart targeted drug delivery carriers. Both of the intermediates and the terminal copolymers were characterized by 1H-NMR and gel permeation chromatography (GPC). The critical micelle concentration (CMC) value is 0.045 mg mL−1 which suggests the micelles are highly stable in dilute solution. TEM and DLS further confirmed the successful formation of micelles with an average size of 61 and 100 nm, PDI of 0.209 and 0.230 for blank and DOX loaded micelles, respectively. The micelles were destructed under a reductive environment, leading to encapsulated drug release. Moreover, fluorescence microscopy demonstrated that the micelles exhibited both a passive and active targeting ability in HeLA cells due to an EPR effect and folate-mediated endocytosis. These results suggested the micelles would provide a favourable platform for constructing excellent drug delivery systems for cancer therapy.