A novel MMP-responsive nanoplatform with transformable magnetic resonance property for quantitative tumor bioimaging and synergetic chemo-photothermal therapy

Quantifying bio-targeted markers in the tumor microenvironment through non-invasive approaches remains challenging. In this study, a novel matrix metalloproteinase-9 (MMP9) responsive nanoplatform (PMP@USPIO/DOX, PMPSD) with transformable magnetic resonance property is designed for quantitative tumor bioimaging and synergetic chemo-photothermal therapy. The nanoplatform acts as a T 2 contrast agent in physiological conditions due to the ultrasmall superparamagnetic iron oxide (USPIO) aggregation state, whereas in the tumor microenvironment, the nanoclusters are dissociated by MMP9, thus transforming the nanoplatform into a T 1 contrast agent. T 1 &T 2 weighted image and T 1 &T 2 maps are utilized to quantitatively study the correlation between MRI signal changes and MMP9 concentrations and to evaluate MMP9 activity. In addition, the PMP@USPIO/DOX nanoplatform possesses excellent photothermal properties. PMPSD combined with laser irradiation is more effective than single chemo-/photothermal therapy, and up-regulation of the MMP9 level in the tumor can further improve the therapeutic effect. The nanoplatform is of great significance in evaluating disease prognosis and non-invasive monitoring of drug release. The concept reported here provides a creative idea for the non-invasive quantitative study of the tumor microenvironment.