Paramagnetic, pH and temperature-sensitive polymeric particles for anticancer drug delivery and brain tumor magnetic resonance imaging

Smart polymer-based theranostic agents often have the problem of a low drug release rate and it is difficult for them to reach the site of brain tumors for magnetic resonance imaging (MRI). To synthesize a theranostic agent for brain tumor MRI with a high drug release rate, paramagnetic, pH and temperature-sensitive polymeric particles (PPPs) are synthesized using a simplified processes in this work. These dually sensitive polymeric particles show negligible cytotoxicity against HeLa and glioma (C6) cells. The obtained polymeric particles can effectively be loaded with the anticancer drug doxorubicin (DOX). In vitro drug release measurements exhibit retarded release profiles when subjected to varying pH or temperature. Moreover, DOX-loaded PPPs exhibit obvious antitumor properties for C6 cells. The percentage of cumulative DOX release is higher than 95% when both pH and temperature are changed. The T₁-weighted relaxivity values at 3 T are 12.41 mM^-1 s^-1 (pH = 6.3) and 10.75 mM^-1 s^-1 (pH = 7.4). In vivo MRI reveals that the PPPs can be effectively imaged in brain tumors (gliomas). These results indicate that the PPPs have great potential in diagnosing and treating glioma.