Synthesis of water-soluble and thermoresponsive phthalocyanine ended block copolymers as potential photosensitizer

A novel zinc(II) tetraaminophthalocyanine ended block copolymer methoxypolyethylene glycol- b -poly(N-isopropylacrylamide) (MPEG- b -PNIPAAM-ZnTAPc) had been synthesized through an easy way. First, the diblock copolymers MPEG- b -PNIPAAM were synthesized by atom transfer radical polymerization (ATRP) and functionalized with one molecule of maleic anhydride (MA) by ATRP, and then reacted with ZnTAPc to form a water-soluble and thermoresponsive photosensitizer . The lower critical solution temperatures for the copolymers can be easily controlled by changing the ratio of MPEG and PNIPAAM. In aqueous solution, the thermosensitive copolymers will self-assemble into micelles and characterized by dynamic light scattering and transmission electron microscopy , and the sizes of micelles will increase with temperature increasing. In the micelles, ZnTAPc will aggregate to induce fluorescence quenching. As a photosensitizer, MPEG- b -PNIPAAM-MA-ZnTAPc can generated singlet oxygen species with good quantum yields (Φ Δ  = 0.23), which were believed to be the major reactive oxygen species. And the copolymer had low dark cytotoxicity and high phototoxicity based on MTT assay, so the MPEG- b -PNIPAAM-ZnTAPc will used in the field of photodynamic therapy and photocatalytic oxidation .