Dynamic Monitoring of Content Variation of Guanosine Triphosphate in Single Cells under External Stimulus with Functionalized Fluorescent/Photothermal Nb ₂ C-MXene Nanoprobes

Photothermal therapy (PTT) has demonstrated significant potential in the ablation of tumors, but understanding of the dynamic molecular changes in intracellular energy metabolism during PTT-induced cell death is less studied, which is helpful for the optimization of the therapeutic approach. Guanosine triphosphate (GTP), is a key nucleotide involved in energy metabolism and cellular processes, playing a critical role in tumor cell proliferation and metabolic reprogramming. Herein, we developed an aptamer-functionalized Nb₂C MXene nanoprobe (FA-Nb₂C-GTP) to monitor dynamic content variation of intracellular GTP during PTT process. Based on fluorescence resonance energy transfer (FRET), the probe exhibits an ″off-on″ fluorescence response upon GTP binding. It exhibits high specificity for GTP (LOD = 15.67 μM), good photothermal conversion efficiency (34.21%), and biocompatibility. During photothermal therapy, FA-Nb₂C-GTP enabled real-time cell imaging of dynamic content variation of GTP. In HepG2 cells, the experiments found that GTP levels initially increased, reaching a peak at 5 min postirradiation with a 232.8% fluorescence enhancement relative to controls, followed by a decline upon extended NIR irradiation exposure. Conversely, HL-7702 cells exhibited minimal GTP fluctuations, with a maximum fluorescence increase of 23.8% at 7 min postirradiation. These results revealed distinct GTP metabolic response behaviors between the tumor and normal cells during PTT-induced apoptosis. The designed FA-Nb₂C-GTP nanoprobe represents a powerful tool for investigating the relationship between energy metabolism and PTT-induced tumor cell death, offering insights for the rational design of targeted PTT agents.