Manganese-Based Magnetic Layered Double Hydroxide Nanoparticle: A pH-Sensitive and Concurrently Enhanced T1/T2-Weighted Dual-Mode Magnetic Resonance Imaging Contrast Agent

The interference effect and lack of selectivity are the bottlenecks for dual-mode magnetic resonance imaging (MRI) contrast agent development. To address these challenges and overcome the single mode imaging contrast limitations, a novel MgMnAl-layered double hydroxide@iron oxide nanoparticle (MgMnAI-LDH@IO NP) has been successfully synthesized as a concurrently enhanced dual-mode contrast agent for MRI of tumor tissues with sensitive pH response and high efficacy. The attachment of iron oxide nanoparticles on the surface of MgMnAl-LDH NPs led to the increased local magnetic field intensity, inducing the concurrent enhancement of both T-1 and T-2 relaxivity. The in vitro MRI demonstrated that the MgMnAl-LDH@IO NP could act as a pH-sensitive contrast agent for both T-1- and T-2-weighted MR imaging (r(1), 5.67 mM(-1) s(-1) under pH 5.0 and 1.98 mM(-1) s(-1) under pH 7.4; r(2), 369.12 mM(-1) s(-1) under pH 5.0 and 225.29 mM(-1) s(-1) under pH 7.4). The biocompatibility of the dual-mode contrast agent was revealed by the cytotoxicity test on fibroblast cells. Further in vivo dual-mode MR imaging exhibited that the MgMnAl-LDH@IO NP showed clear T-1- and T-2-weighted MR imaging of tumor tissues in breast-tumorbearing mice. The facile synthetic method, desirable biocompatibility, sensitive stimuli response, and concurrently enhanced T-1/T-2 MRI signals both in vitro and in vivo encourage the great potential biomedical and clinical applications of MgMnAl-LDH@IO NP in MR imaging with improved accuracy.