Synthesis and characterization of aminoporphyrin-end-functionalized poly(N-isopropylacrylamide) with photodynamic and thermoresponsive effects.

The novel aminoporphyrin-end-functionalized poly(N-isopropylacrylamide) (PNIPAM) polymer H2N-TPP-PNIPAM (TPP = 5,10,15,20-tetraphenyl-21H,23H-porphyrin) behaves as a multifunctional platform that displays a photodynamic effect, thermosensitivity, and fluorescence properties. The polymer was designed by using an asymmetrical aminoporphyrin (i.e., H2N-TPP-Cl) as the initiator for the atom-transfer radical polymerization of N-isopropylacrylamide (NIPAM). The polydispersity index (PDI) obtained by gel-permeation chromatography indicated that the molecular-weight distribution was narrow (1.09<PDI<1.27). The lower critical solution temperatures of H2N-TPP-PNIPAM showed a decreasing trend as the molecular weight was increased as a result of the incorporation of the porphyrin group at the end of the chain. The fluorescence spectra revealed the luminescent properties of the materials. The results of confocal laser scanning microscopy showed that the polymer could enter the cytoplasm through endocytosis. In addition, the multifunctional platform exhibited low toxicity against normal cells (L929) and cancer cells (Hela) and enhanced photodynamic activity towards HeLa cells, without significant necrocytosis towards L929 cells; as a result this material may be useful in the future for practical photodynamic therapy.