The investigation of unique water-soluble heptamethine cyanine dye for use as NIR photosensitizer in photodynamic therapy of cancer cells.

Abstract

In this paper, a unique water-soluble heptamethine cyanine dye as NIR photosensitizer was synthesized to explore its properties associated with potential applications in photodynamic therapy (PDT). In the strategy of designing this photosensitizer, a sulfonic acid was used as a water soluble functional group and linked to the fluorophore through alkyl chains. 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl(Tempo) moiety was used as the a nitroxide spin label in obtaining biochemical reaction information in vivo due to it could greatly increase the inter-system crossing (ISC) process for triplet-state photosensitizers and low toxicity. As expected, the photosensitizers performed well in vitro photodynamic therapy. There were a remarkable absorbance band located at 692 nm and emission peaks falls at 762 nm, the quantum yield (Φf) was calculated to be 12.12% in pure aqueous solution using ICG as standards. The photosensitizer also has high singlet oxygen quantum yield (Φ△) for 16.96% with NIR LED irradiation. This photosensitizer can rapidly produce singlet oxygen and exhibit high phototoxicity under NIR light irradiation. It has excellent cellular uptake ability and better cell compatibility. It was also successfully applied in Near-infrared fluorescence imaging and AO/EB staining. In a whole, the organic dye based on Heptamethine cyanine used as photosensitizer has great potential in vivo cancer treatment.