Synthesis and characterization of photo-responsive flower-like copolymer micelles with o-nitrobenzyl as the junction point.

• ABA amphiphilic triblock copolymer self-assembled into flower-like micelles. • The micelles showed excellent photo-response to irradiation time. • The photolysis rate could be adjusted by changing polymer chain lengths. • DOX-loaded micelles exhibit drug release increased obviously after UV irradiation. The photo-responsive ABA amphiphilic triblock copolymers polylactide-block-poly(ethylene glycol)-block-polylactide with o-nitrobenzyl esters as the photocleavable block-linker (defined as PLA-NB-PEG-NB-PLA), were prepared by controlled ring-opening polymerization (ROP) of D, L-lactide (D, L-LA) using two o-nitrobenzyl groups terminated polyethylene glycol as initiator. Flower-like micelles formed after these copolymers were dissolved in aqueous solution. Introduction of shortened PEG and PLA chains, although resulting in the reduction of micelle sizes, would bring about higher photolysis rate and loading efficiency of DOX. The flower-like micelles showed excellent photocleavage properties, thereby, burst release of DOX could be induced after UV irradiation, which will have potential application in biomedical materials. [ABSTRACT FROM AUTHOR]