Study on Dual Stimuli-Responsive Supramolecular Diblock Copolymers

In this paper, we report the synthesis and characterization of a new stimuli-responsive diblock polymer, i.e., methoxy poly (ethylene glycol)-block-Poly(N-isopropylacrylamide) (mPEG-beta-PNI-PAM), which belongs to the family of supramolecular amphiphiles. For this purpose, beta-cyclodextrin (beta-CD)-functionalized methoxy poly (ethylene glycol) (mPEG-CD) and adamantine (AD)-modified poly(N-isopropylacrylamide) (PNIPAM-AD) were synthesized. The diblock polymer mPEG-beta-PNIPAM was then obtained by host-guest inclusion between mPEG-CD and PNIPAM-AD. The structure and molecular weight of the mPEG-beta-PNIPAM was confirmed by (HNMR)-H-1 and GPC, respectively. Above the lower critical solution temperature (LCST), mPEG-beta-PNIPAM can self-assemble into nano-structures in aqueous solutions with PNIPAM block as the core and mPEG block as the corona. The aggregation behavior of mPEG-beta-PNIPAM were revealed by UV-vis, DLS measurements, and TEM observations. The mPEG-beta-PNIPAM was further utilized to construct Dox@mPEG-beta-PNIPAM micelles at 37 degrees C in phosphate-buffered saline (PBS). No detectable amount of Dox was released from the micelles at 37 degrees C. When cooling to 27 degrees C or adding a competitive reagent, however, release of Dox from the micelles was observed.