Porous gold nanocluster-decorated manganese monoxide nanocomposites for microenvironment-activatable MR/photoacoustic/CT tumor imaging

Stimuli-responsive nanoprobes that integrate multi-modal imaging capacities are highly desirable for precise tumor visualization. Herein, novel porous gold nanocluster-decorated manganese monoxide nanocomposites (MnO@Au NCs) were synthesized via a facile approach. The porous gold nanocluster layer was germinated on the surface of the as-prepared MnO@DMSA NPs through simple reduction of chloroauric acid in the presence of hydroxylamine hydrochloride. The MnO@Au NCs could be effectively internalized by tumor cells and slowly release Mn²⁺ ions within the acidic tumor microenvironment, improving the visualization of the tumor morphology. Benefitting from the porous architecture, the enhanced accessibility of Mn centers to proximal water molecules greatly augmented T₁-weighted MRI contrast capacity. Compared with the conventional Mn-based contrast agents, the porous Au nanoclusters on MnO@Au NCs could delay the release of Mn²⁺ ions and thus effectively prolong the diagnostic time window. The broad near-infrared absorption of MnO@Au NCs features a high photoacoustic imaging depth than that of conventional gold nanospheres. Moreover, the Au nanoclusters exhibited desirable X-ray computed tomography contrast and rapid clearance from the living body. The as-prepared MnO@Au NCs hold great potential for accurate tumor imaging.