Radiosynthesis and In Vitro Bioevaluation of ^99mTc-Temozolomide as a Radiotracer for Glioma Imaging

Background: Temozolomide (TMZ), an alkylating drug used for the treatment of gliomas, has to date not been exploited for its potential role as a radionuclide-imaging probe. This study reports the radiosynthesis of [^99mTc]Tc-TMZ and evaluates its specificity for glioma using C6 cell lines. Methods: TMZ was labeled with ^99mTc, optimized for reaction conditions and radiochemical purity. Physicochemical characterization was performed by evaluating plasma protein binding, stability in saline and serum, and partition coefficient. Furthermore, the cellular uptake and internalization mechanism of [^99mTc]Tc-TMZ were determined in C6 cells. The toxicity of the radiotracer was determined by performing the MTT and hemolysis assays. Results: The radiocomplex was synthesized with >90% radiochemical purity. The radiocomplex exhibited neutral charge, high lipophilicity, low plasma protein binding, and physiological stability in in vitro conditions. Cell binding studies exhibited [^99mTc]Tc-TMZ specificity for C6 cells in a concentration- and time-dependent manner, with maximum uptake at 12.5 μg and passive diffusion as the primary mode of transport. Toxicity studies revealed more than 50% damage to the cells with minimal hemolytic activity at 50 μg concentration of TMZ in radiocomplex. Conclusions:These preliminary findings suggest the specificity of [^99mTc]Tc-TMZ for C6 cells and warrant further exploration as a SPECT radiotracer for glioma imaging.