MaLing Gou and colleagues from the Nano-biomaterials research group at Sichuan University readily prepared Dox/MPEG-PCL micelles by a novel self-assembly method. The technique involves heating an MPEG-PCL aqueous slurry to 50 °C and then incorporating Dox into MPEG-PCL micelles through a pH-induced self-assembly method. The team believes that this self-assembly method may be one of the easiest ways to prepare Dox-loaded polymeric nanoparticles/micelles in the literature.

Dox/MPEG-PCL micelles with a drug loading of 4.2% were monodisperse and ∼20 nm in diameter. Compared with free Dox, the Dox/MPEG-PCL micelles were more effective in inhibiting tumor growth in the subcutaneous C-26 colon carcinoma and Lewis lung carcinoma models, and prolonging survival of mice bearing these tumors. Furthermore, these Dox/MPEG-PCL micelles induced lower systemic toxicity than free Dox.

Real-time analysis

The researchers also examined the extravasation of Dox and MPEG-PCL micelle-encapsulated Dox from vessels to surrounding spaces in vivo in a transgenetic zebrafish model. Taking advantage of the transparency of the zebrafish larva and the visual contrast between Dox and EGFP-exp host endothelial cells, this in vivo analysis was carried out in real time.

The group found that encapsulation of Dox in MPEG-PCL micelles slowed the extravasation of Dox (see images above), which may be one of the reasons for the reduced systemic toxicity of Dox/MPEGPCL micelle treatment, compared with free Dox treatment.

Full results can be found in the journal Nanotechnology.