ß-Cyclodextrin Nanophotosensitizers for Redox-Sensitive Delivery of Chlorin e6.

The aim of this study is to prepare redox-sensitive nanophotosensitizers for the targeted delivery of chlorin e6 (Ce6) against cervical cancer. For this purpose, Ce6 was conjugated with ß-cyclodextrin (bCD) via a disulfide bond, creating nanophotosensitizers that were fabricated for the redox-sensitive delivery of Ce6 against cancer cells. bCD was treated with succinic anhydride to synthesize succinylated bCD (bCDsu). After that, cystamine was attached to the carboxylic end of bCDsu (bCDsu-ss), and the amine end group of bCDsu-ss was conjugated with Ce6 (bCDsu-ss-Ce6). The chemical composition of bCDsu-ss-Ce6 was confirmed with 1H and 13C NMR spectra. bCDsu-ss-Ce6 nanophotosensitizers were fabricated by a dialysis procedure. They formed small particles with an average particle size of 152.0 ± 23.2 nm. The Ce6 release rate from the bCDsu-ss-Ce6 nanophotosensitizers was accelerated by the addition of glutathione (GSH), indicating that the bCDsu-ss-Ce6 nanophotosensitizers have a redox-sensitive photosensitizer delivery capacity. The bCDsu-ss-Ce6 nanophotosensitizers have a low intrinsic cytotoxicity against CCD986Sk human skin fibroblast cells as well as Ce6 alone. However, the bCDsu-ss-Ce6 nanophotosensitizers showed an improved Ce6 uptake ratio, higher reactive oxygen species (ROS) production, and phototoxicity compared to those of Ce6 alone. GSH addition resulted in a higher Ce6 uptake ratio, ROS generation, and phototoxicity than Ce6 alone, indicating that the bCDsu-ss-Ce6 nanophotosensitizers have a redox-sensitive biological activity in vitro against HeLa human cervical cancer cells. In a tumor xenograft model using HeLa cells, the bCDsu-ss-Ce6 nanophotosensitizers efficiently accumulated in the tumor rather than in normal organs. In other words, the fluorescence intensity in tumor tissues was significantly higher than that of other organs, while Ce6 alone did not specifically target tumor tissue. These results indicated a higher anticancer activity of bCDsu-ss-Ce6 nanophotosensitizers, as demonstrated by their efficient inhibition of the growth of tumors in an in vivo animal tumor xenograft study.

Phenethyl Isothiocyanate-Conjugated Chitosan Oligosaccharide Nanophotosensitizers for Photodynamic Treatment of Human Cancer Cells.

The aim of this study is to synthesize phenethyl-conjugated chitosan oligosaccharide (COS) (abbreviated as ChitoPEITC) conjugates and then fabricate chlorin E6 (Ce6)-incorporated nanophotosensitizers for photodynamic therapy (PDT) of HCT-116 colon carcinoma cells. PEITC was conjugated with the amine group of COS. Ce6-incorporated nanophotosensitizers using ChitoPEITC (ChitoPEITC nanophotosensitizers) were fabricated by dialysis method. 1H nuclear magnetic resonance (NMR) spectra showed that specific peaks of COS and PEITC were observed at ChitoPEITC conjugates. Transmission electron microscope (TEM) confirmed that ChitoPEITC nanophotosensitizers have spherical shapes with small hydrodynamic diameters less than 200 nm. The higher PEITC contents in the ChitoPEITC copolymer resulted in a slower release rate of Ce6 from nanophotosensitizers. Furthermore, the higher Ce6 contents resulted in a slower release rate of Ce6. In cell culture study, ChitoPEITC nanophotosensitizers showed low toxicity against normal CCD986Sk human skin fibroblast cells and HCT-116 human colon carcinoma cells in the absence of light irradiation. ChitoPEITC nanophotosensitizers showed a significantly higher Ce6 uptake ratio than that of free Ce6. Under light irradiation, cellular reactive oxygen species (ROS) production of nanophotosensitizers was significantly higher than that of free Ce6. Especially, PEITC and/or ChitoPEITC themselves contributed to the production of cellular ROS regardless of light irradiation. ChitoPEITC nanophotosensitizers showed significantly higher PDT efficacy against HCT-116 cells than that of free Ce6. These results indicate that ChitoPEITC nanophotosensitizers have superior potential in Ce6 uptake, ROS production and PDT efficacy. In the HCT-116 cell-bearing mice tumor-xenograft model, ChitoPEITC nanophotosensitizers efficiently inhibited growth of tumor volume rather than free Ce6. In the animal imaging study, ChitoPEITC nanophotosensitizers were concentrated in the tumor tissue, i.e., fluorescence intensity in the tumor tissue was stronger than that of other tissues. We suggest that ChitoPEITC nanophotosensitizers are a promising candidate for the treatment of human colon cancer cells.