Redox-Responsive Self-Assembly Micelles from Poly(N-acryloylmorpholine-block-2-acryloyloxyethyl ferrocenecarboxylate) Amphiphilic Block Copolymers as Drug Release Carriers

Novel well-defined redox-responsive ferrocene-containing amphiphilic block copolymers (PACMO-b-PAEFC) were synthesized by ATRP, with poly(N-acryloylmorpholine) (PACMO) as hydrophilic blocks and poly(2-acryloyloxyethyl ferrocenecarboxylate) (PAEFC) as hydrophobic blocks. The copolymers were characterized by FT-IR and H-1 NMR spectroscopies and gel permeation chromatography, and the crystalline behavior was determined by X-ray diffraction and small-angle X-ray scattering. The results showed that the size of the lamellar crystals and crystallinity vary with the systematic compositions while the periodic structure of the lamellar stacks has no obvious change. These block copolymers could self-assemble and form globular nanoscaled coreshell micellar aggregates in aqueous solution. The reductive ferrocene groups could be changed into hydrophilic ferrocenium via mild oxidation, whereas the polymer micelles at the oxidation state could reversibly recover from their original states upon reduction by vitamin C. The tunable redox response was investigated and verified by transmission electron microscopy, ultravioletvisible spectroscopy, cyclic voltammetry, and dynamic light scattering measurements. The copolymer micelles were used to entrap anticancer drug paclitaxel (PTX), with high drug encapsulation efficiency of 61.4%, while the PTX-loaded drug formulation exhibited oxidation-controlled drug release, and the release rate could be mediated by the kinds and concentrations of oxidants. MTT assay was performed to disclose the biocompatibility and security of the copolymer micelles and to assess anticancer efficiency of the PTX-loaded nanomicelles. The developed copolymer nanomicelles with reversible redox response are anticipated to have potential in targeted drug delivery systems for cancer therapy.