In this work chemical functionalization of carbon nanotubes was conducted with the aim of improving their ability to be integrated into biological systems. Functionalized SWNT demonstrated to be an excellent vehicle to translocate a highly conjugated organic fluorophore across the cell membrane while causing little toxicity to the cells. Functionalized SWNT were introduced into different lines of the primary brain tumor cells Glioblastoma Multiforme (GBM). Once within the cell interior, the optical properties of the SWNT were used for both fluorescent imaging characterization and selective killing of tumor cells that had exhibited high SWNT uptake levels upon exposure to NIR radiation. Propidium iodide (PI) was employed as an indicator to determine the number of cells with compromised plasma membrane. Cell surviving ratio of as little as 10-20 percent were found in samples with intracellular nanotubes exposed to NIR radiation while a cell surviving ratio of about 95 percent was typical in irradiated samples without intracellular nanotubes. Control samples showed cell surviving ratios comparable to exposed samples without intracellular nanotubes. This study reveals new insights upon the influence of SWNT optical properties in the physicochemical processes within cells and how they can be used to develope therapy for cancerous brain tumors.