This coating minimizes nonspecific interactions and enhances the specific binding of QDs conjugated with targeting agents, such as immunoglobulin G (IgG) or streptavidin, to biomarkers such as HER2 on breast cancer cells.163 Compared with organic dyes, the polymer coating also supports the retention of QDs' superior optical properties, including brighter fluorescence and higher photostability, facilitating the subcellular imaging of actin fibres, microtubules, and nuclear antigens. Here, ERBB2 is linked to breast cancer.