Magnetic nanosheets: from iron oxide nanocubes to polydopamine embedded 2D clusters and their multi-purpose properties

We here develop stable bidimensional magnetic nanoclusters (2D-MNCs) of iron oxide nanocubes (IONCs) arranged in thin nanosheets of closed-packed nanocubes. The assembly occurs by means of a two-step approach: in the first one, the ionic surfactant, sodium dodecyl sulfate (SDS), acts as a transient water transfer agent and as 2D clustering agent to induce formation of a monolayer of nanocubes arranged in thin nanosheets. Next, the addition of dopamine followed by solution basification, induces the in situ polymerization of dopamine with a tunable shell tickness depending on the dopamine amount, which helps to compact the clusters and ensures the long term water stability of the clusters. TEM, cryo-EM, and SAXS techniques helped to reveal structural features of the 2D-clusters. The pH-dependent degradation properties of polydopamine, enable to disassemble the clusters in acidic tumour microenviroment leading to a four-fold increase in the magnetic particle imaging signal and a concomitant increase of the magnetic heat losses of these clusters, makes them appealing in magnetic hyperthermia, while the shortening of T2 relaxation time suggests their use as contrast in magnetic resonance imaging. Finally, with crystal violet dye, used as drug molecule, the feasibility to release payloads pre-encapsulated with the polydopamine polymer shell has been also shown.