Poly(ethylene oxide)--polyphosphester-based Paclitaxel Conjugates as a Platform for Ultra-high Paclitaxel-loaded Multifunctional Nanoparticles.

A new type of degradable, nanoscopic polymer assembly containing ultra-high levels of drug loading covalent attachment within amphiphilic core-shell nanoparticle morphology has been generated as a potentially effective and safe anti-cancer agent. Poly(ethylene oxide)--polyphosphoester-based paclitaxel drug conjugates (PEO--PPE--PTX) were synthesized by rapid, scalable and versatile approach that involves only two steps: organocatalyst-promoted ring-opening-polymerization followed by click reaction-based conjugation of a PTX prodrug. Variations in the polymer-to-PTX stoichiometries allowed for optimization of the conjugation efficiency, the PTX drug loading and the resulting water solubilities of the entire polymer and the PTX content. The PEO--PPE--PTX formed well-defined micelles in aqueous solution, with a PTX loading capacity as high as 65 %, and a maximum PTX concentration of 6.2 mg/mL in water, which is 25000-fold higher than the aqueous solubility of free PTX. The positive cell-killing activity of PEO--PPE--PTX against several cancer cell lines is demonstrated, and the presence of pendant reactive functionality provides a powerful platform for future work to involve conjugation of multiple drugs and imaging agents to achieve chemotherapy and bioimaging.