Figure 4

Detection of cell-nanoparticle association by fluorescent immunodetection and confocal microscopy. Her2 antigen was detected on the surface of MCF7/Her2-18 cells by indirect immunofluorescence assay (a) (green label), whereas MDA-MB-231 cells demonstrated little to no Her2 expression on the surface, although antigen was detected within cytoplasmic structures in some cells (b) (green label). CHO cells are negative for Her2 (c), whereas negative control samples (d) demonstrate undetectable background labeling with the Alexa-fluor-labeled secondary antibody. Cells were counterstained with rhodamine phalloidin (red label) to visualize cell perimeters. A second set of cells was incubated with anti-Her2-labeled nanoparticles, and then fixed cells were incubated with fluorescently labeled secondary antibody to detect the anti-Her2-labeled nanoparticles and counterstained with rhodamine phalloidin (red label). Anti-Her2-conjugated nanoparticles were detected uniformly on the cell surface of MCF7/Her2-18 cells (e, f) (arrows). MDA-MB-231 cells demonstrate a low level of cell surface-associated anti-Her2-conjugated nanoparticles (g) (arrows), whereas no anti-Her2-conjugated nanoparticles were detected on CHO cells (h). Scale bars = 10 μM (a-e, h) or 5 μM (f, g). CHO, Chinese hamster ovary; Her2, human epidermal growth factor-like receptor 2.