Fluorescent Nanodiamonds Based Theranostic Platform for pH‐Sensitive Drug Delivery and Quantum Sensing

Abstract Breast cancer is the most common cancer in women worldwide. Triple negative breast cancer (TNBC) is particularly problematic due to the poor prognosis and limited treatment options. Here, nanodiamond particles are synthesized for delivering the cancer drug Diazoxide (DZX) to TNBC cells. The multifunctional nanodiamond (ND) platform integrates pH‐sensitive drug release and advanced quantum sensing capabilities, enabling precise drug delivery and monitoring of intracellular redox dynamics. Due to the nitrogen‐vacancy (NV) centers in the diamond particles, they can be imaged. Further, quantum sensing is demonstrated specifically at the location where the drug is released. After 24 h of treatment at 10 µg mL −1 diamond‐DZX complex (equivalent to 2.75 µM DZX), diamond relaxometry reveals a decreased radical load in the endo/lysosomal regions, while MitoSOX fluorescence indicates elevated mitochondrial ROS (O 2 − ) levels, suggesting the activation of intracellular redox homeostasis. By combining controlled drug delivery with advanced quantum sensing, this work provides novel insights into DZX's mechanism of action, particularly its role in modulating mitochondrial ROS and cellular redox balance. This multifunctional nanoplatform demonstrates significant potential for advancing targeted cancer therapy and redox biology research.