SURG-11. PATHOLOGICAL INVESTIGATION OF NOVEL SPRAY-TYPE FLUORESCENT PROBES FOR BRAIN TUMORS

Abstract OBJECTIVE A fluorescent probe such as 5-aminolevulinic acid achieves greater extent of resection in glioma surgery and thus serves as a valuable surgical adjunct. However, its sensitivity and specificity are yet to be perfectly satisfactory. Our novel spray-type fluorescence system using green hydroxymethyl rhodamine green (HMRG) probes has been tested for brain tumors. In this study, we investigated on red dimethyl silicone rhodamine 600 (2MeSiR600) probes, which have a higher sensitivity for peptidase activity than HMRG probes. MATERIALS AND METHODS Fresh tumor tissues as well as fresh frozen tissues harvested from gliomas resected at our institutions were used in this study. The probe library included over 400 types with different combinations of amino acids attached to 2MeSiR600. Fluorescence intensity was measured over time after probes were applied to homogenized lysates made from fresh frozen tissues. Fluorescent probes which clearly discerned the tumor area from the peripheral area were selected, and then applied to fresh tumor tissues to confirm their selectivity. Tumor tissues were fixed with formalin and stained with hematoxylin and eosin. Immunohistochemistry staining was also performed. The correlation between fluorescence intensity and histopathology including cell density and MIB-1 labeling index was investigated. RESULTS Probe screening demonstrated some 2MeSiR600 probes exhibited significantly higher fluorescence intensity in the peripheral area compared to the tumor area, which was confirmed when they were applied to fresh tumor tissues. CONCLUSION 2MeSiR600 probes which selectively fluoresce the peripheral area may enable highly selective tumor recognition in conjunction with 5-aminolevulinic acid or our HMRG probes.