Abstract
The photosensitizing ability of C
60
/2-hydroxypropyl-
β
-cyclodextrin (HP-
β
-CyD) nanoparticles under visible light irradiation was studied by electron spin resonance (ESR) and phototoxicity on cancer cells. In addition, the photoinduced antitumor effect to the tumor-bearing mice was evaluated. C
60
nanoparticles were prepared by grinding a mixture of HP-
β
-CyD. The resulting C
60
/HP-
β
-CyD nanoparticles were highly-sensitive to visible light and generated higher levels of
1
O
2
than protoporphyrin IX (PpIX). C
60
/HP-
β
-CyD reduced the viability of cancer cells (HeLa cells and A549 cells) in response to irradiation by visible light in a dose-dependent manner. The IC
50
values of the C
60
/HP-
β
-CyD nanoparticles was 10
μ
M for HeLa cells and 60
μ
M for A549 cells at an irradiation level of 35 mW/cm
2
. The photodynamic effect of C
60
/HP-
β
-CyD nanoparticles on the
in vivo
growth of mouse sarcoma S-180 cells was evaluated after intratumor injection. The outcome of PDT by C
60
/HP-
β
-CyD was directly dependent on the dose of irradiated light. Treatment with C
60
/HP-
β
-CyD nanoparticles at a C
60
dose of 2.0 mg/kg under visible light irradiation at 350 mW/cm
2
(63 J/cm
2
) markedly suppressed tumor growth, whereas that at 30 J/cm
2
was less effective. These findings suggest that C
60
/HP-
β
-CyD nanoparticles represent a promising candidate for use in cancer treatment by PDT.