Protease-triggered targeted delivery of gold nanorods into tumor

Gold nanorods have a strong surface plasmon band at the near infrared region. The absorbed light energy is then converted to heat. Since near infrared light can penetrate deeply into tissue, gold nanorods are expected to be used as a contrast agent for bioimaging using the near infrared light and photosensitizers for photothermal therapy. In this study, to achieve targeted delivery of the gold nanorods to tumor, PEG-peptide-modified gold nanorods were constructed. As the peptide part, substrate sequences for proteases that are specifically expressed in tumor were employed. After reacting with the proteases, dramatic spectral changes were observed, indicating that aggregation of the gold nanorods occurred. The aggregation depended on density of the modified PEG-peptide on the surface of the gold nanorods. When the gold nanorods were injected into tumor-bearing mice, higher accumulation of the gold nanorods in the tumor was detected compared with the case of PEG-peptide (control sequence)-modified gold nanorods. Use of peptide sensing extracellular matrix of tumor is expected to be a powerful strategy for diagnosis and therapy of tumor using gold nanorods.