Preparation of metal phthalocyanine (MPc)–polymer complexes: the possible anti-cancer properties of FePc–polymer complexes

We have succeeded in preparing various water-soluble metal phthalocyanine (MPc)–polymer complexes, wherein the metal moiety is lithium, iron, cobalt, copper, zinc, or tin, and the polymer is one of the following water-soluble polymers: polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), or polyvinyl alcohol (PVA). Among all MPc–polymer complexes, the iron phthalocyanine (FePc)–PVP complex in water showed the largest and sharpest absorption peak at ∼700 nm in UV–Vis absorption spectrum, which indicates that FePc–polymer complexes in water are easily prepared and the degree of stacking of FePc in the complexes, very small, such as that of a monomer or a similar structure. Conversely, the polymer chains including those of PEG, PVP, and dextran have high biological affinity as well as flexibility. Speculatively, the FePc–polymer (e.g., PEG, PVP, and dextran) complexes adsorbed onto the surface of a cancer cell might break it via the irradiation of near-infrared light having a wavelength of ∼700 nm. Furthermore, chlorophyll a–polymer complexes, previously prepared by our group, might similarly break a cancer cell because these complexes showed a large and sharp absorption peak at ∼700 nm in UV–Vis spectrum.