Abstract 3469: Photodynamic diagnosis (PDD) and therapy (PDT) with dendrimer porphyrin micelle

Abstract

Abstract [Background and purpose] We previously reported that the efficacy of photodynamic therapy (PDT) with dendrimer phthalocyanine-loaded micelles (DPc/m). However, monitoring of this photosensitizer by the clue of fluorescence is quite difficult because of the low intrinsic fluorescence originating from phthalocyanine, thus other fluorescence dye such as Alexa is required for the monitoring. For resolving this problem, we developed a novel micelle-based photosensitizer loading dendrimer porphyrin (DP). The DP-loaded micelles (DP/m) intensely emit fluorescence from porphyrin without an additional fluorescence labeling. The aim of this study was to verify practical effectiveness of DP/m by comparing that of DP on PDD and PDT. [Materials and Methods] For in vitro cytotoxicity tests, rat bladder carcinoma cells (AY-27) were incubated with DP/m for 4 h and were exposed to laser light (635 nm, 100 J/cm2). One day after PDT, cell viability was measured by WST-8 assay. Distribution of DP/m in cellular organelles was investigated using fluorescence markers of cellular organelles by a confocal laser scanning microscope. In addition, we examined in vivo fluorescence imaging using an orthotopic bladder tumor model established by inoculating AY27 cells in female Fischer F344 rats via transurethral catheterization. Four hours after intravenous administration of DP/m, the bladders were extracted and fluorescence image was obtained of bladder. [Results] DP and DP/m without light irradiation were basically non-toxic (low dark toxicity), showing cell viability being > 85% at the concentration up to 17 μM. However, photoirradiated DP and DP/m induced the high level of cytotoxicity: survival rate was less than 5%. PDT using DP/m showed an approximately 15 times of cytotoxicity when compared with PDT using DP. The results suggested that DP/m highly accumulate in cancer cells and can provide a significant photodynamic effect leading to cell damage. Confocal laser scanning microscopic studies showed that DP/m exhibited preferential accumulation in lysosomes through endocytosis and retention in the cells. When DP/m were injected (i.v.) into the bladder tumor animal models, fluorescence from the DP/m were clearly visualized in accordance with tumor distribution. We detected fluorescence even when a size of tumor was less than 1 mm, thus enabling optical imaging with excellent contrast between tumor and surrounding normal tissue. A study of PDT in vivo is now carried out. [Conclusion] We developed dendrimer porphyrin-loaded micelles (DP/m), which were effective for both PDD and PDT. An excellent detection of tumor was achieved owing to the intense fluorescence of DP/m and highly accumulation in tumors. The preferable DP/m uptake in tumors resulted in effective phototoxicity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3469. doi:1538-7445.AM2012-3469