Two water-soluble porphyrin self-assemblies consisting of bisacetylene- and monoacetylene-linked conjugated bis(imidazolylporphyrin) have been synthesized. Two-photon absorption (2PA) cross section values in water were determined as 7500 GM for bisacetylene- and 7900 GM for monoacetylene-linked bisporphyrin by femtosecond open-aperture Z-scan measurement. These values were almost the same as those for the similar structure reported previously in CHCl(3). Therefore, the structure is suggested to be similar in CHCl(3) and aqueous solutions. Both compounds were found to efficiently generate singlet oxygen upon one-photon irradiation in a manner similar to protoporphyrin, as demonstrated by the time-resolved luminescence measurement at the characteristic band of 1270 nm. Photocytotoxicities for HeLa cancer cells were examined and found to be as high as those of hematoporphyrin, demonstrating that these newly prepared compounds are potential candidates as 2PA-photodynamic therapy agents.

O 2 signal gradually decreased with a low peak, whereas at a high fluence rate it decreased immediately with a high peak. Consequently, the cumulative 1 O 2 at a low fluence rate was higher, which thus induced a strong photodynamic effect. The proportion of apoptosis to necrosis might therefore be dependent on the peak and duration of the 1 O 2 signal. A low fluence rate tended to induce apoptotic change, whereas a high fluence rate tended to induce necrotic change. Conclusions:The results of this study suggested that the monitoring of 1 O 2 enables us to predict the photodynamic effect, allowing us to select the optimal laser conditions for each patient.

The possibility of 5-aminolaevulinic acid-based photodynamic therapy (ALA-PDT) for liver cancer was investigated using a chemically induced hepatocellular carcinoma (HCC) model. Endogenously synthesised protoporphyrin IX (PpIX) following the administration of ALA is an effective photosensitiser for PDT. We determined the fluorescence intensity of PpIX in HCC and nontumoral tissue in the liver. 5-Aminolaevulinic acid was intravenously injected to male Fisher rats with HCC at a dose of 500 mg kg À1 , and the fluorescence intensity in each tissue sample excised from liver was measured with a spectrofluorometer at 1, 3 and 6 h after administration. Fluorescence intensity was at a peak of 3 h after administration in both HCC and nontumoral tissue. The accumulation of PpIX in HCC was higher than that in the nontumoral tissue at 1 h (Po0.001) and 3 h (Po0.05) after ALA administration. Based on these results, PDT was performed on HCC at 3 h after 500 mg kg À1 ALA administration before laser irradiation of 30 J per tumour. Antitumour effect was more evident in HCC than in the nontumoral tissue surrounding HCC. These findings suggest the possibility to detect HCC by fluorescence and to treat HCC by light.