A phthalocyanine-peptide conjugate with high in vitro photodynamic activity and enhanced in vivo tumor-retention property |
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Authors: | Ke Mei-Rong Yeung Sin-Lui Fong Wing-Ping Ng Dennis K P Lo Pui-Chi |
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Institution: | Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, PR China. |
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Abstract: | A novel zinc(II) phthalocyanine conjugated with a short peptide with a nuclear localization sequence, Gly-Gly-Pro-Lys-Lys-Lys-Arg-Lys-Val, was synthesized by click chemistry and a standard Fmoc solid-phase peptide synthesis protocol. The conjugate was purified by HPLC and characterized with UV/Vis and high-resolution mass spectroscopic methods. Both this compound and its non-peptide-conjugated analogue are essentially non-aggregated in N,N-dimethylformamide and can generate singlet oxygen effectively with quantum yields (Φ(Δ)) of 0.84 and 0.81, respectively, relative to unsubstituted zinc(II) phthalocyanine (Φ(Δ) =0.56). Conjugation of the peptide sequence, however, can enhance the cellular uptake, efficiency in generating intracellular reactive oxygen species, and photocytotoxicity of the phthalocyanine-based photosensitizer against HT29 human colorectal carcinoma cells. The IC(50) value of the conjugate is as low as 0.21 μM. In addition, the conjugate shows an enhanced tumor-retention property in tumor-bearing nude mice. After 72 h post-injection, the dye concentration in the tumor was significantly higher than that in other organs. The results suggest that this phthalocyanine-peptide conjugate is a highly promising photosensitizer for photodynamic therapy. |
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