Development of a new autofluorescence probe for the analysis of normal and tumour brain tissues

Fluorescence spectroscopy of endogenous emission of brain tumors, in particular glioblastoma multiforme, will be used for intraoperative localization of brain tumor margins. Our future surgeon's probe aims to discriminate tumor from normal brain tissues using beta and autofluorescence detection at the same time. Within this study we have implemented C6 glioma cells into rat brains to analyze the endogenous fluorescence of tumor and normal rat brain tissue. Systematic differences have been observed when comparing the autofluorescence spectra obtained from white and grey matters: both the fluorescence intensity and the shape of the spectra differ. These results were obtained by means of a 2-fiber probe, one used to guide the laser to the tissue, the other for fluorescence light collection. Excitation light was delivered by a 405 nm picosecond laser and fluorescence detection was realized by a CCD-camera. In parallel we have developed brain phantoms allowing systematic analysis of fiber - sample geometries. Based on gelatin gels, they include silica particles with 235 and 329 nm diameters to simulate the diffusion characteristics of the tissue, ink for the absorption characteristics of the tissue and organic dyes like Rhodamin B to replace biofluorophores.