Diamond-Based Quantum Sensing of Free Radicals in Migrating Human Breast Cancer Cells

Cell migration is a crucial parameter for disease progression in cancer. It is known that ROS levels are involved in the regulation of the migration process, however, the exact role of free radical generation and where it occurs is unknown. Here we use a diamond-based quantum sensing technique to detect free radical generation during cancer cell migration in real time with subcellular resolution. We investigated highly metastatic MDA-MB-231 human breast cancer cells and observed free radical formation after 16 hours of starvation and 24 h of migration under low-serum conditions. Intracellular diamond dynamics was monitored at different migration points (0, 12, and 24 h), and cell morphology was evaluated. Additionally, the number of focal adhesions was analyzed as an indicator of the migratory potential of the cells. All the parameters were addressed using a homemade script on the FIJI platform. We further measured free radical generation under NOX2 inhibition by apocynin. We found that free radical levels decreased after 24 h treatment with 36 µg/mL apocynin while the levels of ROS increased and also the migratory capacity of the cells. Our results evidence the complexity of the redox regulation in migrating cancer cells and offer a novel approach to specifically and locally interrogate pivotal players of the oxidative network behind metastatic success.