Zhou et al. reported the design of gold/polydopamine-Methylene Blue@Bovine Serum Albumin-glutaraldehyde-Transferrin composite particles, which were used to visualize the particles inside the targeted 4T1 breast cancer cells, by surface-enhanced Raman scattering and fluorescence imaging, thus, validating both the feasibility of Tf as a targeting moiety and the biocompatibility of PDA [33]. Here, TF is linked to breast cancer.