Fig. 3
Determination of tracking sensitivity of biofluorescent imaging in vitro and in vivo. a Among the serial dilutions, 104 labeled haMSCs displayed a marginal fluorescence signal that could be detected above the phosphate-buffered saline (PBS) background. b Quantification of the fluorescence signal in a showing that the detection threshold in vitro is between 103 and 104 cells (107 and 108 photons/s/cm2). c Remarkable fluorescent signals were displayed in rats injected with 106 and 105 cells, while signals of 104 cells were undetectable, suggesting that the in vivo detection threshold of DiD-haMSCs was between 105 and 104 cells. d Quantification of the fluorescence signal in c showing that the detection threshold in vivo is between 104 and 105 cells (8 × 107 and 5 × 108 photons/s/cm2). Data were representative of two repetitions (n = 2)