Light/temperature dual-responsive ABC miktoarm star terpolymer micelles for controlled release

A novel light- and temperature-responsive amphiphilic ABC miktoarm star terpolymer consisting of hydrophilic poly(ethylene glycol) (PEG), light-responsive poly(2-nitrobenzyl methacrylate) (PNBM), and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) arms, PEG(-b-PNBM)-b-PNIPAM, was synthesized via a combination of atom transfer radical polymerization (ATRP) and click reaction. In aqueous solution, the obtained miktoarm star terpolymer self-assembled into spherical micelles with PNBM cores and hybrid PEG/PNIPAM coronas. When heating above the phase transition temperature of PNIPAM, larger aggregates with mixed PNBM/PNIPAM cores and PEG coronas were formed. Upon UV light irradiation, the initial micelles were disrupted and reassembled into some large micelle complexes. Fluorescence emission measurements showed that Nile red encapsulated in the polymeric micelles could be released by stimuli of UV light or temperature change. More interestingly, the UV triggered release could be strengthened in basic conditions but weakened in acidic conditions. The prepared light- and temperature-responsive polymeric micelles may have great potential in applications such as nanocarriers and biotechnology for controlled drug and bioagent delivery.