Development and characterization of stabilized double loaded mPEG-PDLLA micelles for simultaneous delivery of paclitaxel and docetaxel

Objective: Double loaded micelles (DLM) in which paclitaxel (PTX) and docetaxel (DTX) were co-solubilized with monomethoxy poly(ethylene glycol)-block-poly(d,l-lactide) (mPEG-PLA) copolymer were prepared and evaluated in an aim to investigate the effect of a combination of PTX and DTX on the stability of mPEG-PLA micelles compared to single drug-loaded micelles (SDM), especially that recent clinical anticancer formulations are limited by the existence of toxic excipients and stability issues.

Materials and methods: The SDM and DLM of PTX and DTX were prepared by a solvent evaporation method. Micellar size, size distribution, drug loading content and drug release were investigated. Transmission electron microscopy was used to investigate the stabilization mechanism.

Results: The drug loading efficiency of both PTX and DTX in DLM and SDM were 25% and 10%, respectively. ¹H NMR showed a successful encapsulation of both drugs in the polymeric micelle. DLM showed better physical stability at drug concentrations higher than 1?mg/mL compared to SDM. Moreover, DLM, SDM-PTX and SDM-DTX were stable for 24, 9 and 1?h, respectively. The stabilization mechanism of DLM was investigated, a network structure of DLM was observed in TEM graphs. Furthermore, DLM showed complete and faster drug release compared to SDM. mPEG-PLA double loaded micelles can deliver two poorly water soluble anticancer drugs at clinically relevant doses. The obtained results offer a promising alternative for double drug therapy without any formulation associated undesirable effects and encourage further in vivo development and optimization of the DLM as a drug delivery system for anticancer drugs.