Spectral features of ultraviolet laser-induced fluorescence in human glioblastoma tissues

Today, various fluorescent methods are widely used for intraoperative diagnosis of malignant brain tumors. However, all of them rely on exogenous fluorophores. Meanwhile, UV-induced autofluorescence may also be of interest. The aim of the study was to identify characteristic spectra of glioblastoma tissues using ultraviolet laser-induced fluorescence spectroscopy. Material and methods. Morphological and laser fluorescence studies were conducted on resected glioblastoma tissues from three patients. Microscopy and morphometry with hematoxylin and eosin staining were employed. Using a tunable wavelength laser (210–290 nm), excitation-emission matrices of laser-induced fluorescence were measured. Results and discussion. Principal component analysis (narrow peak method) enabled the identification of three component spectra contributing to the fluorescence of the samples. These components correspond to different forms of tryptophan, with intensity maxima at wavelengths of 315 nm and 330 nm, and connective tissue. The primary malignant brain tumors studied were significantly heterogeneous; however, the ratio of the intensities of the fluorescent components differs for samples with varying tissue elements content – tumor parenchyma, necrotic parenchyma, and stromal elements. Conclusions. Spectral changes associated with tryptophan fluorescence, quantitatively determined by the ratio of the intensities of the above-described components, can be used as a new biomarker for glioma and may serve as the basis for developing an optical, minimally invasive method for determining tumor boundaries.