The obtained aptamers specifically bound to the primary tumor of glioblastoma and did not stain healthy brain cells (Patent RU 2 654 665 C2). The putative targets of the obtained aptamers were glial fibrillary acidic protein (GFAP), tubulin alpha-1C chain (TUBA1C) and myelin basic protein (MBP) acidic protein with post-translational modifications and pancreatic lipase-related protein 3. The 3D structure of the Gli-233 aptamer was determined using small-angle scattering and computer simulation methods. Aptamers conjugated with a fluorescent Brilliant Violet 650 dye (Gli-233BV) did not show in vivo toxicity in preclinical animal studies and were used for tumor visualization during fluorescence-guided surgery in patients. The anti-GBM aptamer was conjugated with a fluorescent Brilliant Violet 650 dye (Gli-233BV) and applied on tissues during the surgical removal.