Preparation and characterization of the ion-fixed mixed micelles with superior stability

The inherent instability of micelles remains a main challenge for antitumor drug delivery, the objective of this study is to prepare and characterize the ion-fixed mixed micelles with significantly improved stability. The mixed micelles and ion-fixed mixed micelles combining the carboxy-containing PLA (PLA-COO(-)) and mPEG-PLA were formed by inserting PLA-COO(-) into micellar core without and with metal ions, respectively. The critical micelle concentration (CMC) of mixed micelle depended on the origin PLA length in the mPEG-PLA, whereas kinetic stability of the mixed micelles was significantly improved, irrespective of the PLA length. However, curcumin (Cur)-loaded mixed micelles did not show higher physical stability upon dilution and Cur-micelle bonding constant due to the lower loading space. On the contrary, the ion-fixed mixed micelles formed in the presence of CaCl2 solution showed a high physical stability upon dilution due to the solidification of micellar core by forming the more hydrophobic (PLA-COO(-))2 Ca(2+) complex. The Cur-loaded ion-fixed mixed micelles showed the comparable cellular uptake of Cur and cytotoxicity in comparison with mPEG-PLA micelles. Our study highlights a universal combining strategy of ion-fixed mixed micelles with superior stability to individual micelles for antitumor drug delivery.