Fig. 2

Lipid-coated SPIO nanoparticles exhibit superior reduced nonspecific uptake rate compared with uncoated SPIO nanoparticles. TEM images of a non-coated SPIO nanoparticles and b lipid-encapsulated SPIO nanoparticles acquired from a different manufacturer. Scale bar, 10 nm. c Quantification of adsorption rate for non-coated SPIO and lipid-encapsulated SPIO nanoparticles in the U-87MG cell line. Indicated nanoparticles were added to the U-87MG culture medium at final concentrations of 1, 0.5, 0.25, 0.1, 0.05, 0.025, 0.01, and 0 mg/ml before incubating the cells at 37 °C for 1 or 24 h. The cells were then subjected to a colorimetric ferrozine assay to measure the Fe concentration. d The toxicity of lipid-encapsulated SPIO nanoparticles to U-87MG and U-251 cells was evaluated using an MTT viability assay. Lipid-encapsulated SPIO nanoparticles with final Fe concentrations of 0.2, 0.1, 0.05, 0.01, and 0 μg/ml in culture media were incubated with the indicated cells for 24 h before subjecting them to the MTT assay. Error bars, SEM