Biomass-Based Carbon Dots for Fe³⁺ and Adenosine Triphosphate Detection in Mitochondria

Real-time live-cell monitoring of Fe3+ and adenosine triphosphate (ATP) in mitochondria important for cellular functions and related to different diseases is highly desired, yet lack study. Herein, carbon dots, green bean (GB)-carbon dots (CDs), were made from GB through easy one-step hydrothermal treatment. GB-CDs were in spherical form with a diameter of 13 ± 3 nm, negatively charged, and green emissive. GB-CDs contained amino groups, which enabled their binding to Fe3+, resulting in their fluorescence quenching. Based on this, GB-CDs were employed to detect Fe3+ with high selectivity, showing a linear detection range of 10–70 μM and a detection limit of 3.6 nM. Furthermore, the addition of ATP can recover the fluorescence quenching of GB-CDs by Fe3+. Therefore, the GB-CD + Fe3+ system was deployed to assay ATP with a linear detection range of 50–600 μM and a detection limit of 60 nM, exhibiting high sensitivity and specificity. GB-CDs and GB-CDs + Fe3+ were individually harnessed to assess Fe3+ in tap water and ATP in fetal bovine serum. More importantly, GB-CDs can enter cells to localize in mitochondria for mitochondrial imaging with high biocompatibility and superior photostability. As a result, GB-CDs and GB-CD + Fe3+ system were implemented to track Fe3+ and ATP in mitochondria of A549, respectively. This study provides a potent tool to monitor Fe3+ and ATP in mitochondria, expanding the application of CDs as biosensors for biological compounds in subcellular organelles.