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 mu M 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 mu M 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.