Green light-emitting polyepinephrine-based fluorescent organic dots and its application in intracellular metal ions sensing

• Green light-emitting polyepinephrine fluorescent organic dots are presented.
• The PEP-FODs is used to detect Fe2+, Fe3+, and Cu2+.
• The detection procedures of metal ions are label free and rapid.
• The PEP-FODs possess good solubility, low cytotoxicity, and biocompatibility.

In this paper, we present a class of bio-dots, polyepinephrine (PEP)-based fluorescent organic dots (PEP-FODs) for selective and sensitive detection of Fe2+, Fe3+, and Cu2+. The PEP-FODs were derived from epinephrine via self-polymerization at relatively low temperature down to 60 °C with low cytotoxicity and relative long lifetime (7.24 ns). The surface morphology and optical properties of the synthesized PEP-FODs were characterized. We found that the diameters of PEP-FODs were mainly distributed in the narrow range of 2–4 nm with an average diameter of 2.9 nm. An optimal emission peak located at 490 nm was observed when the green light-emitting PEP-FODs were excited at 400 nm. It is discovered that Fe2+, Fe3+, and Cu2+can strongly quench the fluorescence of PEP-FODs through the nonradiative electron-transfer. The detection limit of 0.16, 0.67, and 0.15 μM was obtained for Fe2+, Fe3+, and Cu2+, respectively. The independent sensing platform of Fe2+, Fe3+, and Cu2+could be established by using NaF as a complexing agent and by regulating the reaction time between NaF and metal ions. Cell viability studies reveal that the as-prepared PEP-FODs possess good solubility and biocompatibility, making it as excellent imaging nanoprobes for intracellular Fe2+, Fe3+, and Cu2+sensing. The developed PEP-FODs might hold great promise to broaden applications in nanotechnology and bioanalysis.