Novel unsymmetrical silicon(IV) phthalocyanines as highly potent anticancer photosensitizers. Synthesis, characterization, and in vitro photodynamic activities

Abstract

A series of novel unsymmetrical silicon (IV) phthalocyanines (SiPcs) di-substituted axially with tyramine and different oligomeric ethylene glycol moieties have been synthesized by alkoxy exchange reactions, and their singlet oxygen quantum yields (ΦΔ) and in vitro photodynamic activities have also been evaluated. The unsymmetrical SiPcs 2–5 show slightly higher photosensitizing efficiency (ΦΔ = 0.08–0.12) than the corresponding symmetrical SiPc 1 (ΦΔ = 0.05), but are less efficient compared to the symmetrical SiPc 6 (ΦΔ = 0.33). All the compounds exhibit high photocytotoxicities against BGC-823 cancer cells with IC50 values ranging from 3 nM to 20 nM. Particularly for the unsymmetrical SiPc 5, the IC50 value toward BGC-823 cells is significantly lower than its corresponding symmetrical SiPcs 1 and 6, which could be attributed to its higher cellular uptake. In addition, SiPc 5 can essentially bind to mitochondria and induces cell death of BGC-823 cells mainly through apoptosis. So SiPc 5 is a highly promising photosensitizer for photodynamic therapy.