Activatable Fluorescence/MRI Bimodal Platform for Tumor Cell Imaging via MnO2 Nanosheet-Aptamer Nanoprobe

A novel dual-activatable fluorescence/MRI bimodal platform is designed for tumor cell imaging by using a redoxable manganese dioxide (MnO2) nanosheet-aptamer nanoprobe. The redoxable MnO2 nanosheet acts as a DNA nanocarrier, fluorescence quencher, and intracellular glutathione (GSH)-activated Mill contrast agent. In the absence of target cells, neither fluorescence signaling nor Mill contrast of the nanoprobe is activated. In the presence of target cells, the binding of aptamers to their targets weakens the adsorption of aptamers on the MnO2 nanosheets, causing partial fluorescence recovery, illuminating the target cells, and also facilitating the endocytosis of nanoprobes into target cells. After endocytosis, the reduction of MnO2 nanosheets by GSH further activates the fluorescence signals and generates large amounts of Mn2+ ions suitable for MM. This platform should facilitate the development of various dual-activatable fluorescence/MRI bimodalities for use in cells or in vivo.