Hydrophilic K2Mn4O8 nanoflowers as a sensitive photothermal theragnosis synergistic platform for the ablation of cancer

Abstract

Achieving cancer diagnosis and treatment simultaneously, multifunctional nanomaterials lead the trend in the development of nanomedicine. Manganese-based compounds have been well developed as excellent magnetic resonance (MR) imaging contrast agents, while they have not been demonstrated as photothermal agents (PTAs) due to their unsatisfactory near-infrared photoabsorption. Herein, we report a hydrophilic flower-like K₂Mn₄O₈ superstructure self-assembled by ultrathin nanosheets that can work simultaneously as a PTA and an ultrasensitive T₁-weighted magnetic resonance imaging (T₁-MRI) enhancing agent. These K₂Mn₄O₈ nanoflowers are efficient vehicles transforming 808 nm laser energy into thermal energy and then leading to the effective ablation of cancer cells in vitro and in vivo. Importantly, with a high longitudinal relaxivity (r₁) of 4.6 mM⁻¹ s⁻¹, they also act as quite impressive T₁-MRI enhancing agents. Both in vitro and in vivo experiments confirmed their great biocompatibility, low toxicity and high photothermal conversion capability. This is the first application of K₂Mn₄O₈ as a PTA and would hopefully promote other Mn-based theranostics.