Novel Zn(II) phthalocyanine with tyrosine moieties for photodynamic therapy: Synthesis and comparative study of light-associated properties

Octa-(4-tyrosylamido) phenyl substituted Zn(II) phthalocyanine (ZnPcTyr8) was synthesized and characterized as potential photosensitizer for photodynamic therapy (PDT). The new ZnPcTyr8 was evaluated in comparison to recently synthesized tetra-(4-tyrosylamido) phenyl substituted Zn(II) phthalocyanine (ZnPcTyr) and used as a standard unsubstituted Zn(II) phthalocyanine (ZnPc). The photophysical properties of absorption and fluorescence, and photochemical properties of singlet oxygen generation and photostability as well as in vitro photocytotoxicity property were investigated. The irradiation from a light-emitting diode (LED 665 nm) with a dose of 50 J cm−2 and a fluence of 60 mW cm−2 was applied. The obtained results suggested improved photophysicochemical properties of singlet oxygen generation for tyrosine-conjugated Zn(II)-phthalocyanines. In addition the tyrosine substitution to ZnPc is liable for gentle photocytotoxicity which is in contrast to the harsh phototoxic effect determined for ZnPc on tumor and normal cell lines. Among both tyrosine substituted Zn(II) phthalocyanines, a novel ZnPcTyr8 has advantages of water solubility and proper values of the main photophysicochemical properties responsible for PDT efficacy.