Carbon Nanodots/Ag Composites Enable Real-Time Monitoring of Intracellular Adenine Dynamics Under Oxidative Stress in Cancer Cell Line

Adenine is a vital purine nucleobase that plays essential roles in enzyme regulation, cell signaling, energy metabolism, and the storage of genetic information. As a structural component of key biomolecules such as ATP, NAD+, SAM, and cAMP, its imbalance is associated with immune responses, cardiovascular dysfunction, and cancer. Therefore, accurate and efficient detection of adenine is critical for clinical research and biological diagnostics. In this study, we developed an innovative nitrogen-doped carbon quantum dot complex integrated with silver ions (N-CQDs/Ag composite) of ≈25 nm for the selective detection of adenine via a simple fluorescence turn-on mechanism. Techniques including DLS, TEM, FT-IR, EDX, UV–vis, and fluorescence spectroscopy were employed to characterize the morphology and properties of the nanosensor. The probe exhibited a remarkable detection limit of 0.076 μM, indicating high sensitivity. Importantly, it enabled successful intracellular detection of endogenous adenine in HeLa cells, even under stress conditions. This approach offers a rapid, cost-efficient, and biocompatible platform for real-time monitoring of adenine, with strong potential for applications in bioanalysis and diagnostics, thereby serving as a promising tool for intracellular biomarker monitoring and disease-related diagnostics.