In this study, a facile method to fabricate reduction-responsive core-crosslinked micelles via in situ thiol-ene "click" reaction was reported. A series of biodegradable poly (ether-ester)s with multiple pendent mercapto groups were first synthesized by melt polycondensation of diol poly(ethylene glycol), 1,4-butanediol, and mercaptosuccinic acid using scandium trifluoromethanesulfonate [Sc(OTf)(3)] as the catalyst. Then paclitaxel (PTX)-loaded core-crosslinked (CCL) micelles were successfully prepared by in situ crosslinking hydrophobic polyester blocks in aqueous media via thiol-ene "click" chemistry using 2,2'-dithiodiethanol diacrylate as the crosslinker. These PTX-loaded CCL micelles with disulfide bonds exhibited reduction-responsive behaviors in the presence of dithiothreitol (DTT). The drug release profile of the PTX-loaded CCL micelles revealed that only a small amount of loaded PTX was released slowly in phosphate buffer solution (PBS) without DTT, while quick release was observed in the presence of 10.0 mM DTT. Cell count kit (CCK-8) assays revealed that the reduction-sensitive PTX-loaded CCL micelles showed high antitumor activity toward HeLa cells, which was significantly higher than that of reduction-insensitive counterparts and free PTX. This kind of biodegradable and biocompatible CCL micelles could serve as a bioreducible nanocarrier for the controlled antitumor drug release. (C) 2015 Wiley Periodicals, Inc.