Objective: To explore the optimal concentration of polyethylenimine-superparamagnetic iron oxide (PEI2k-SPIO) particles for labeling bone marrow mesenchymal stem cells (BMSCs) in vitro, then to demonstrate the imaging characteristics of the cells by 7.0-T MR scanner. The lowest cell quantity and the optimal cell quantity detected on MR was observed.
Methods: Cells at 2nd passage were inoculated into the 6-hole plate with cover glass. The different concentrations of PEI2k-SPIO (5 microg/mL, 7 microg/mL, 10 microg/mL, 15 microg/mL, 20 microg/mL) were added into different holes, respectively. After labeled with different concentrations of PEI2k-SPIO, the Prussian blue stain was used for determining the labeling efficiency. MTT growth curves were used to identify the activity of BMSCs and to determine the optimal threshold of SPIO nanocomposite particles labeled the stem cells at different PEI2k-SPIO concentrations (7, 10, 15, 20 microg Fe/mL medium). To definite the lowest cells quantity and the optimal observable cells quantity on MR imaging, 1 x 10(6), 1 x 10(5), 1 x 10(4) and 1 x 10(3) cells labeled with optimal threshold of PEI2k-SPIO and 1 x 10(6) cells unlabeled suspended in 0.2 mL agarose (10 g/L), respectively undergone MR scan.
Results: MTT growth curves showed the optimal threshold of PEI2k-SPIO labeled BMSCs was 7 microg/mL, which indicates has no adverse effects on the growth of stem cells. At the opimal concentration (7 microg Fe/mL), the lowest observable cell quantity of PEI2k-SPIO-labeled cells for MRI was 1 x 10(4), and the optimal observable cell quantity was 1 x 10(6).
Conclusion: At the opimal concentration, adverse effect to stem cell activities had not be detected when were labeled with PEI2k-SPIO and the clearly image of MRI of labeled BMSCs could be obtained.