J. Parhi, A. Ghosh, S. Saha, D. Zaveri, A. Majumder, S. Tallur, A. Majumder, K. Saha
Glioblastoma (GBM) is a highly aggressive cancer with poor prognosis despite temozolomide(TMZ) treatment. TMZ induces oxidative stress, causing persistent redox alterations. We report the first use of nitrogen-vacancy centers in nanodiamonds as quantum sensors for T1 relaxometry in fixed GBM cells, detecting stable paramagnetic signatures linked to chemotherapy-induced persistent oxidative damage. U87-MG cells treated with TMZ show dose-dependent T1 shortening, consistent with conventional ROS fluorescence assays. TBHP studies confirm that the T1 response reflects accumulated redox adducts. Measurements remain robust across fixation and permeabilization protocols. Since drug-resistant GBM cells preserve antioxidant signatures, unchanged T1 times after treatment may indicate early resistance phenotypes. This fixed-tissue compatible readout could stratify patient response, guide adaptive therapy, and support biopsy-based diagnostics and post-treatment drug analysis in routinely preserved clinical specimens enabling retrospective studies and better outcomes for future personalized oncology decision making pathways.