Objective: To synthesize poly(ethylene glycol)-poly(lactic acid)-poly(β-amino ester) (PBAE) block polymer and prepare paclitaxel-loaded micelles to enhance its solubility in aqueous milieu. Method: PBAE was synthesized by Michael addition reaction

its structure was characterized by 1H-NMR

its dissociation contant of a base (pKb) was determined by acid-base titration

critical micelle concentration (CMC) of copolymer was measured by pyrene fluorescence spectroscopy.Paclitaxel loaded copolymer micelles were prepared by membrane hydration methods.Drug loading efficiency (DL) and entrapment efficiency (EE) of micelles were evaluated by high-performance liquid chromatography (HPLC).The size and size distribution of micelles were determined by nanoparticle size analyzer. The structure of micelles was manifested by transmission electron microscopy.In vitro release was performed in phosphate buffered saline at different pH values. Result: CMC of PELA and PBAE were 3.31

4.79 mg ·L-1

pKb values of them were 7.1 and 6.5

their DL were 12.37% and 12.05%

EE were 70.55% and 68.53%

respectively.Paclitaxel loaded micelles were stable up to one week at 4 ℃.In vitro release study showed that drug release from PELA micelles increased slightly with decrease of pH.However

drug release accelerated obviously upon acidic environment (pH 6.5 and 5.5) from pH responsive polymer micelles. Conclusion: PBAE shows high performance in increasing paclitaxel solubility

high drug loading and long stability

as well as pH controlled drug release from micelles.