EPR-Detectable and pH-Responsive Drug-Loaded Micelles: Preparation and in vitro Evaluation

pH-Responsive micelle (PA-pH-TEMPO) modified by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was prepared via polymerization of acetylene using Schiff base as acid responsive group. The structure of the PA-pH-TEMPO was characterized by ¹H-nuclear magnetic resonance (¹H-NMR), Fourier transform infrared (FT-IR) and electron paramagnetic resonance (EPR), respectively. Furthermore, doxorubicin (DOX), model anticancer drug, was encapsulated in the PA-pH-TEMPO to form DOX-loaded micelles (DOX@PA-pH-TEMPO) through a membrane dialysis method. The results of the experiments showed that the PA-pH-TEMPO had no significant cytotoxicity against L929 and HeLa cells. And the drug loading content and drug entrapment efficiency of the DOX@PA-pH-TEMPO micelles were determined to be 2.58% and 32.09%, respectively. The DOX@PA-pH-TEMPO micelles exhibited obvious pH responsiveness and sustained release properties, and showed a strong inhibitory effect on HeLa cells. The in vitro cellular uptake experiments of PA-pH-TEMPO and DOX@PA-pH-TEMPO demonstrated that HeLa cells showed good uptake against these materials, and an obvious EPR signal could be detected.