To recognize prostate cancer cells, the AuNPs were further functionalized with a bombesin (BBN) peptide analog ([7,8,9,10,11,12,13,14] BBN) or with a Lys-Urea-Glu (LUG) motif for the targeting of the gastrin releasing peptide receptor (GRPr) or the prostate-specific membrane antigen (PSMA), respectively. Here, GRPR is linked to prostate cancer.