Figure 2

(A) Light micrographs showing the effect of SPION concentration on the uptake of iron oxide nanoparticles in cultured PPCs by Prussian blue staining. Few Prussian-blue positive cells were detected in the 10 μg Fe/ml SPIONs group, and more positive cells were present in the groups treated with concentrations of SPIONs of more than 20 μg Fe/ml. However, numerous Feridex-PLL complexes deposited on the cellular surface were observed in groups treated with 20 to 70 μg Fe/ml (arrows indicate Feridex-PLL complexes on the cellular surface). The deposition of complexes on the cellular surface was significantly decreased in groups treated with more than 80 μg Fe/ml SPIONs, and most of the Feridex-PLL complexes were phagocytized into the cytoplasm (arrowheads indicate Feridex-PLL complexes inside cells). These results suggested that 100 μg Fe/ml of SPIONs was an optimal concentration. (B and C) Bar graphs showing the effect of SPION concentration on the labeling efficiency and cell viability. The results are shown as the mean ± SD, n = 8 (independent experiments); ***P < 0.001. (D) In the final stage of differentiation, non-labeled and labeled cells showed expression of insulin (red fluorescence), C-peptide (green fluorescence), glucagon (red fluorescence), and colocalized insulin/C-peptide (orange fluorescence). PPCs were used as a negative control. Real-time PCR analysis of β-cell-specific genes: (E) Isl-1, (F) PDX-1, and (G) insulin expression in PPCs and non-labeled, and labeled ICCs. (H) ELISA measurements of the C-peptide content in PPCs and non-labeled, and labeled ICCs. The results shown are the mean ± SD, n = 4 (independent experiments); ***P < 0.001. Scale bars represent 100 μm.