Synthesis and photoactivity of pH-responsive amphiphilic block polymer photosensitizer bonded zinc phthalocyanine

A zinc tetraaminophthalocyanine derivative, zinc tetra(methacryloyl moiety)aminophthalocyanine (MeZnAPc) (with a double bond) was synthesized by the reaction between zinc tetraaminophthalocyanine (ZnTAPc) and methacryloyl chloride. Atom transfer radical polymerization (ATRP) was employed as the polymerization technique to obtain a novel pH-responsive polymeric photosensitizer (PEG110-b-P(DPA n -co-MeZnAPc m )) by copolymerizing of methoxypolyethylene glycols (MPEG) (as reducing agent), 2-(isopropylamino)ethyl methacrylate (DPA) and MeZnAPc. This photosensitizer was characterized by UV-vis spectroscopy, FTIR, 1H NMR, etc. The results indicated that the photosensitizer presented the well pH-responsive behavior around the pH range 6.0–6.5 and the high photoactivity to 1,3-diphenylisobenzofuran (DPBF). The result of photocatalysis oxidation of l-tryptophan (l-Try) suggested that zinc phthalocyanine could present high photoactivity due to its dispersivity at pH 5.5 without formation of micelles, and its photoactivity decreased dramatically at pH 7.4 due to wrapping ZnTAPc into the micelles. Therefore, the novel pH-responsive polymeric photosensitizer has better application prospects in the field of photodynamic therapy.