| Summary: | 碩士 === 高雄醫學大學 === 醫藥暨應用化學研究所碩士班 === 94 === Near-infrared fluorescence (NIRF) light has been applied to image various biological events in vivo, because it penetrates tissue more efficiently than light in the visible spectrum. An 11-amino acids peptide substrate was designed and synthesized for specific enzyme prostate-specific antigen (PSA). A near-infrared (NIR) cyanine fluorochrome serving as the optical imager can be used for in vivo imaging of enzyme activity and is attached to the amino terminal of peptide substrate with specificity for PSA. A protected graft copolymer (PGC) molecule consisting of a poly-L-lysine (PL) backbone and methoxy polyethylene glycol (MPEG) side chains was prepared. Excess peptide substrate was separated from peptide-PGC conjugate by Sephadex G-25 size-exclusion chromatography and was determined by measuring fluorescein absorption at 493.5 nm. The fluorescence intensity of prostate peptide substrate enhances higher intensity in the presence of PSA enzyme when compared with scrambled control peptide. The present studies have identified a peptide substrate sequence with a high degree of specificity for PSA. This sequence but not a scrambled control sequence showed enzyme specificity in vitro and in vivo. Using tumor models in nude mice expressing the targeted PSA, it could be shown that the tumor generated sufficient NIR signal to be directly detectable in the presence of this NIRF probe. Besides, we also design and synthesize two peptide sequences for Nasopharyngeal Carcinoma (NPC). These peptide sequences use the active side to target the specific receptor in the surface of the NPC tumor cell. To apply these peptide sequences in the optical imaging, we used FITC to conjugate with the peptide sequences to form the NPC peptide fluorescence probe. In the flow cytometric analyzer experiment, these two probes showing the highly activity for NPC cell were obtained. For these two kinds of fluorescence probes, in vitro and in vivo experiments were performed the feasibility of optical imaging to apply the detection and diagnosis for cancer disease.
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