Mixed Polymeric Micelles for Paclitaxel Delivery: Preparation and Characterization

To address the limitations of commercial vehicles for paclitaxel (PTX) delivery, this study investigated mixed micelles as a novel delivery system for this drug. By incorporating PCL₅₀₀₀-PEG₅₀₀₀ into DSPE-PEG₂₀₀₀ at 99.5:0.5 and 99:1 molar ratios, we aimed to enhance drug loading and biocompatibility. The resulting systems were characterized using a range of physicochemical and biological characterization. The system achieved a low critical micelle concentration (CMC) of 1.9 × 10^-5 mol/L, ensuring stability upon dilution. Optimized formulations (99.5:0.5 and 99:1 molar ratios) exhibited a small hydrodynamic diameter (∼11 nm) and near-neutral zeta potential. Small-range X-ray scattering (SAXS) analysis confirmed a spheroidal core-shell structure, where the addition of 0.5% PCL₅₀₀₀-PEG₅₀₀₀ increased drug loading capacity to 3.1 ± 0.05% w/w. Thermal analysis confirmed the successful integration of copolymers and their thermal stability. Notably, the cytotoxicity of this formulation was comparable to that of commercial formulations, while exhibiting negligible hemolysis (<2%), indicating a substantially improved safety profile compared with Cremophor-based vehicles. These findings highlight the potential of these mixed micelles as a biocompatible, high-capacity delivery platform for intravenous cancer chemotherapy.