Self-assembled nanoparticles from thiol functionalized liquid crystalline brush block copolymers for dual encapsulation of doxorubicin and gold nanoparticles†
We synthesized new amphiphilic brush liquid crystalline block copolymers (brush-chol-BCP) comprised of polymethacrylates bearing polyethylene oxide (PEO) in one block and polymethacrylates bearing a cholesterol mesogen with a hemitelechelic thiol end group. Polymethacrylate bearing PEO (PMA-g-PEO) was first synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT) and used as a macro-chain transfer agent to prepare block copolymer (PMA-g-PEO)-b-PC5MA-thioester (brush-chol-BCP-thioester). Brush-chol-BCP-thiol was obtained by the reduction of a thioester to thiol in the presence of butylamine. Gold nanoparticles (AuNPs) were prepared in situ with the brush-chol-BCP-thiol template via the reduction of gold ions and were stabilized by directly anchoring to the brush-chol-BCP-thiol chains through the coordination bonds with the thiol groups in the copolymer. The hydrophobic anticancer drug doxorubicin (DOX) was successfully encapsulated into AuNP-templated brush-chol-BCP-thiol via physical entrapment to form dual-encapsulated NPs with a high drug loading of 21.4% (w/w) and a high encapsulation efficiency of 85.6%. The dual-encapsulated NPs had an average size of 157 nm, spherical shape, excellent stability, and a sustained drug release pattern. More importantly, the dual-encapsulated NPs could be effectively internalized by human cervical cancer cells (Hela) and showed dose-dependent cytotoxicity, while the blank nanoparticles were non-cytotoxic at the tested concentrations. The results indicate that the brush-chol-BCP-thiol and their nanoparticles are promising carriers for dual encapsulation and delivery of an anticancer drug and metal nanoparticles.