Manganese oxide doped carbon dots for temperature-responsive biosensing and target bioimaging

We report on the synthesis of manganese oxide doped CDs (MnOx-CDs) by a hydrothermal strategy using manganese (III) acetylacetonate (Mn(III) (C5H7O2)(3)) as the only raw materials. The MnOx-CDs exhibit water solubility, favorable biocompatibility, low cytotoxicity, and show blue fluorescence with excitation/emission maxima at 326/442 nm with a quantum yield of 11.3%, allowing efficient cellular imaging. The MnOx-CDs have a reversible temperature-sensitive fluorescent property in vitro within 10-60 degrees C, which can also be used as a sensitive thermometer in living cells. By a scratch assay, the MnOx-CDs can restrain the migration of HepG2 cancer cells, which make the MnOx-CDs be attractive candidates for liver cancer adjuvant treatment. Besides, the fluorescence of the MnOx-CDs is quenched in the presence of Fe3+ due to the formation of a nonfluorescent MnOx-CDs-Fe3+ complex between oxygen-containing groups on the surface of MnOx-CDs and Fe3+, and the quenched fluorescence of MnOx-CDs can be turn-on by dissociation of MnOx-CDs-Fe3+ complexes by biothiols including L-cysteine, homocysteine and glutathione. Therefore, the Fe3+ and biothiols can be sequentially detected with high reliability and accuracy via exploiting the on-off-on nanosensor at room temperature, respectively. Further application to detection biothiols in human serum indicated that the probe was practicality and feasibility in medical field. (C) 2020 Elsevier B.V. All rights reserved.