Molecular-target-based anticancer photosensitizer: synthesis and in vitro photodynamic activity of erlotinib-zinc(II) phthalocyanine conjugates.

Targeted photodynamic therapy is a new promising therapeutic strategy to overcome growing problems in contemporary medicine, such as drug toxicity and drug resistance. A series of erlotinib-zinc(II) phthalocyanine conjugates were designed and synthesized. Compared with unsubstituted zinc(II) phthalocyanine, these conjugates can successfully target EGFR-overexpressing cancer cells owing to the presence of the small molecular-target-based anticancer agent erlotinib. All conjugates were found to be essentially non-cytotoxic in the absence of light (up to 50 μM), but upon illumination, they show significantly high photo-cytotoxicity toward HepG2 cells, with IC50 values as low as 9.61-91.77 nM under a rather low light dose (λ=670 nm, 1.5 J cm(-2) ). Structure-activity relationships for these conjugates were assessed by determining their photophysical/photochemical properties, cellular uptake, and in vitro photodynamic activities. The results show that these conjugates are highly promising antitumor agents for molecular-target-based photodynamic therapy.