In Vitro Evaluation of the Biocompatibility and Stability of Fluorescent Dil Dye on Mouse Embryonic Fibroblast Cells

There are few methods for cell labeling in basic studies of cell-migration, tissue engineering, and cell therapy. Recent progress in cell trackers has led to an increasing number of clinical trials involving the treatment of various diseases based on cell transplantation. In this study, we investigated the effects of different concentrations of DiI as a cell labeling dye on the viability and proliferation of mouse embryonic fibroblasts (MEFs). MEFs were divided into two groups of control and experimental (treated with Dil dye). We treated MEFs with three concentrations of the dye and after 1, 5, 7 and 14 days, these cells were analyzed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and 4’, 6-diamidino-2-phenylindole (DAPI) staining. Also, the stability of the dye in treated MEFs was examined by immunofluorescence. Our results showed that cell viability was significantly different between the groups that received Dil at the concentrations of 1 and 2 µg/mL and the control group. However, cell viability was not significantly different between the group that received Dil (0.5 µg/mL) and the control group. Therefore, Dil at concentrations higher than 0.5 µg/mL was toxic for MEFs. We suggest that Dil dye, which is concentration-dependent, can be used as a safe and stable fluorescent dye for cell labeling both in-vivo and in-vitro.