Cancer targeting can be used for both tumor diagnosis and therapy. Recently, gold nanopar-ticles (AuNPs) have found utility in this field as they are very small in size, and thus display anenhanced permeability and retention effect, allowing them to be taken up by tumor cellsthrough “passive targeting.” However, this accumulation is non-specific. Conversely, AuNPsfunctionalized with targeting entities such as peptides, antibodies, or small molecules canspecifically target tumors through interaction with cancer-specific protein receptors. In thisstudy, targeted AuNPs were developed using an azide-modified peptide that was able toreact with alkyne-functionalized AuNPs through an interfacial strain-promoted azide-alkyne cycloaddition. Small (3 nm) AuNPs were made water-soluble through PEGylationand functionalized with dibenzocyclooctyne to add the alkyne functionality. For thetargeting entity, a pan-bombesin peptide ([D-Phe6,β-Ala11,Phe13,Nle14]bombesin(6–14))was chosen as it binds to all four receptor subtypes of the gastrin releasing peptide receptor,which is highly expressed in prostate cancer. Prostate cancer (PC-3) cells were incubatedwith the targeted AuNPs and studied via transmission electron microscopy. AuNPsconjugated with bombesin showed higher accumulation in PC-3 cells than either theblocking or control studies. These results suggest that these small, water-soluble,bombesin-functionalized AuNPs have potential applications in targeting prostate canceras diagnostic or therapeutic entities.
