Varian inova 400 spectrometer

A cytospin of 100 × 10³ cells was prepared for all labeled cells which were fixed in 3:1 methanol:acetic acid. Iron-labeled cells were stained with Perl’s Prussian blue (PPB) to identify iron in cells¹⁵ . ¹⁹F-labeled cells were labeled with nuclear fast red to assess for PFPE nanodroplets^{11 (link)}. Microscopy of these slides was conducted using the EVOS imaging system (M7000, Thermo Fischer Scientific). The mean intracellular ¹⁹F content in MSC was measured by NMR using a Varian Inova 400 spectrometer (Varian Inc, Paulo Alto, USA) and methods previously described^{11 (link)}.

The compounds were synthesized and characterized according to the method reported in our previous studies (Li et al., 2015 (link); Qu et al., 2020 (link)), in briefly, a mixture of aromatic aldehyde (10 mmol) and 4-hydroxycoumarin (20 mmol), or A mixture of 3,5-cyclohexanedione (10 mmol), 3-cyanobenzaldehyde (10 mmol), malononitrile (10 mmol) and 4-(dimethylamino) pyridine (DMAP) (1 mmol) was dissolved in 100 ml of ethanol. A few drops of piperidine were added, and the mixture was stirred for 3 h at room temperature. After the completion of reaction as determined by TLC, water was added until precipitation occurred. After filtering the precipitates, all the compounds were sequentially washed with ice-cooled water and ethanol and then dried under a vacuum. Infrared spectra were measured using a Brucker Equinox-55 spectrophotometer (Bruker Optics, Ettlingen, German). ¹H NMR spectra, ¹³C NMR spectra, and mass spectra were tested using the Varian Inova-400 spectrometer (Varian Inc, CA, United States), Bruker Avance III spectrometer (Bruker Optics), and micrOTOF-Q II mass spectrometer (Bruker Optics), respectively (Schemes 1, 2).