Hydroxyl Radical-Responsive Nanoprobe Enables Ratiometric Fluorescence Monitoring of Cancer Cell Treatment Response

The detection of the hydroxyl radical (•OH) within the tumor cells is essential for understanding oxidative stress dynamics and drug resistance in cancer therapy. Herein, we report the development of a responsive ratiometric fluorescent nanoprobe, BSA-Rb@LDH-TPA, for the selective and sensitive detection of •OH. The nanoprobe integrates terephthalic acid (TPA) as a •OH-recognition unit within layered double hydroxide (LDH) nanoparticles, stabilized by bovine serum albumin (BSA) conjugated with Rhodamine B (Rb) as a reference dye. Upon interaction with •OH, TPA is converted into its hydroxylated derivative (hTPA), yielding a robust fluorescence signal at 427 nm, while Rb emission at 573 nm remains stable, enabling accurate ratiometric quantification (F427/573). The nanoprobe demonstrated a low detection limit (8.6 nM), high selectivity toward •OH, and negligible cytotoxicity. Applications in both wild-type (WT-4T1) and anticancer drug-resistant (DOXR-4T1) cancer cells revealed distinct •OH levels, highlighting its potential to discriminate drug-sensitive and drug-resistant cancer cell phenotypes. Additionally, the probe effectively monitored •OH production induced by DOX and ultrasound treatment, validating its utility in evaluating combinational therapeutic strategies. This nanoprobe offers a promising platform for optimizing cancer treatment protocols through real-time redox analysis.