Mesoporous MnSiO3@Fe3O4@C nanoparticle as pH-responsiveT1-T2* dual-modal magnetic resonance imaging contrast agent for tumor diagnosis

Abstract

Mesoporous structured MnSiO $ _3 $ @Fe $ _3 $ O $ _4 $ @C nanoparticles (NPs) were prepared via a facile and efficient strategy, with negligible cytotoxicity and minor side efforts. The as-prepared MnSiO $ _3 $ @Fe $ _3 $ O $ _4 $ @C NPs hold great potential in serving as pH-responsive $ T_1 $ - $ T_2 $ $ ^* $ dual-modal magnetic resonance (MR) imaging contrast agents. The released Mn $ ^{2+} $ shortened $ T_1 $ relaxation time, meanwhile the superparamagnetic Fe $ _3 $ O $ _4 $ enhanced $ T_2 $ contrast imaging. The release rate of Mn ions reaches 31.66% under the condition of pH $ = $ 5.0, which is similar to tumor microenvironment and organelles. Cytotoxicity assays show that MnSiO $ _3 $ @Fe $ _3 $ O $ _4 $ @C NPs have minor toxicity, even at high concentrations. After intravenous injection of MnSiO $ _3 $ @Fe $ _3 $ O $ _4 $ @C NPs, a rapid contrast enhancement in tumors was achieved with a significant enhancement of 132% after 24 h of the administration. Moreover, a significant decreasement of 53.8% was witnessed in $ T_2 $ MR imaging signal. It demonstrated that MnSiO $ _3 $ @Fe $ _3 $ O $ _4 $ @C NPs can act as both positive and negative MR imaging contrast agents. Besides, owing to the pH-responsive degradation of mesoporous MnSiO $ _3 $ , MnSiO $ _3 $ @Fe $ _3 $ O $ _4 $ @C NPs can also be used as potential drug systems for cancer theranostics.