Multibranched gold nanoparticles (AuNPs) conjugated to catechol-containing SLC7A5 ligands, l-dopa, and d-dopa were found to be highly accumulated in various breast cancer cell lines (MCF-7, MDA-MB-231, MDA-MB-468, and MDA-MB-453). This evidence concerns the gene SLC7A5 and breast cancer.