Manganese-Based Magnetic Layered Double Hydroxide Nanoparticle: A pH-Sensitive and Concurrently Enhanced...

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 (MgMnAl-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 T₁ and T₂ relaxivity. The in vitro MRI demonstrated that the MgMnAl-LDH@IO NP could act as a pH-sensitive contrast agent for both T₁- and T₂-weighted MR imaging (r₁, 5.67 mM^-1 s^-1 under pH 5.0 and 1.98 mM^-1 s^-1 under pH 7.4; r₂, 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 T₁- and T₂-weighted MR imaging of tumor tissues in breast-tumor-bearing mice. The facile synthetic method, desirable biocompatibility, sensitive stimuli response, and concurrently enhanced T₁/T₂ 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.