Mixed micelles made of Pluronic P 105 (P 105) and poly(ethylene glycol)-phosphatidyl ethanolamine conjugate (PEG-PE) were prepared. The interaction of Pluronic and PEG-PE was studied and the interaction parameter,6 and critical micelle concentration (CMC) were used to evaluate the micellar stability toward dilution. The results showed that certain mixed micelles were more stable than pure Pluronic micelles upon dilution. The mixed micelles were used to trap the poorly soluble anticancer drug camptothecin (CPT). The cytotoxicity of the CPT-loaded mixed micelles against MCF-7 cancer cell was higher than that of CPT-loaded P105 micelles and much higher than that of the free drug. (c) 2007 Elsevier Inc. All rights reserved.