Immunofluorescence analysis of Goat anti-Mouse IgG Secondary Antibody, Alexa Fluor 488-10 nm colloidal gold was performed using MCF-7 cells stained with Cytokeratin 19 (RCK108) Mouse Monoclonal Primary Antibody (Product # MA5-12613). The cells were fixed with 4% paraformaldehyde for 10 minutes, permeabilized with 0.1% Triton™ X-100 for 10 minutes, blocked with 1% BSA for 1 hour and labeled with Mouse primary antibody (1:250 dilution) for 3 hours at room temperature. Goat anti-Mouse IgG Secondary Antibody, Alexa Fluor 488-10 nm colloidal gold (Product # A-31561) was used at a concentration of 1 µg/mL in phosphate buffered saline containing 0.2 % BSA for 45 minutes at room temperature, for detection of cytokeratin 19 in the cytoplasm (Panel a: green). Nuclei (Panel b: blue) were stained with DAPI in SlowFade® Gold Antifade Mountant (Product # S36938). F-actin was stained with Rhodamine Phalloidin (Product # R415, 1:300) (Panel c: red). Panel d represents the composite image. No nonspecific staining was observed with the secondary antibody alone (panel f), or with an isotype control (panel e). The images were captured at 60X magnification.