Preparation and Characterization of pH-responsive Polyurethane Micelles

Tao Zhai ,Ya-yuan Guan, Jian-bin Luo

A new type of pH-responsive multi-blocked polyurethane for drug delivery applications was prepared and characterized by GPC, ¹H-NMR and FT-IR. Then, polyurethane micelles was prepared by dialysis method, and the critical micelle concentration was 2.5×10^-3 g/L as measured by fluorescence technique. TEM and DLS analysises showed that the size of spherical micelles increased from 89.2nm at physiological pH 7.4 to 320 nm at an acidic environment, i.e. pH 5.5, the pH value of intracellular microenvironment of cancer cells. Finally, a hydrophobic anti-cancer drug methotrexate (MTX) was used as a model drug to study the drug release profiles of the drug loaded micelles at neutral and acid environment. The results showed that the drug release is much faster at pH 5.5 than that at pH 7.4. Therefore, the synthesized polyurethanes are promising to be used as pH-responsive drug carriers.