Paclitaxel-loaded Pluronic nanoparticles formed by a temperature-induced phase transition for cancer therapy

We prepared nanoparticles by a temperature-induced phase transition in a mixture of Pluronic F-68 and liquid PEG (polyethylene glycol, molecular weight: 400) containing paclitaxel (PTX) with a fast, simple, continuous and solvent-free process. The liquid PEG is used as solubilizer of PTX and the polymer for the encapsulation of PTX is composed of Pluronic F-68. At the phase transition temperature, the polymer mixture was changed to the liquid phase, and stirring the liquid polymer mixture formed emulsions composed of PEG containing PTX and liquidized Pluronic F-68. On the nanometer scale, PEG containing PTX was encapsulated by Pluronic F-68 by cooling to 0 °C to form Pluronic nanoparticles. The morphology and size distribution of the prepared Pluronic nanoparticles were observed using FE-SEM and TEM, and a particle size analyzer and cryo-TEM were used to observe the shape of paclitaxel-loaded Pluronic nanoparticles in an aqueous state. To apply Pluronic nanoparticles as a delivery system for cancer therapy, the release pattern of PTX, a model anti-cancer drug, was observed and the tumor growth was monitored by injecting the PTX-loaded Pluronic nanoparticles into the tail veins of tumor-bearing mice. We also evaluated the time-dependent excretion profile, in vivo biodistribution, circulation time, and tumor targeting ability of PTX-loaded Pluronic nanoparticles using non-invasive live animal imaging technology. In the early stage within 7 h of release, the loaded PTX was rapidly released and the sustained release was observed for up to 48 h. In vivo studies, PTX-loaded Pluronic nanoparticles were observed with higher anti-tumor efficacy compared with PTX formulated in Cremophor EL.