Fe3+-assisted nitrogen-doped carbon dot fluorescence switch for ultrasensitive detection of acetyl-CoA in live microalgal cells

Acetyl-CoA (AcCoA) functions as a pivotal metabolic node that regulates diverse cellular pathways in organisms (e.g., microalgae). Real-time monitoring of intracellular metabolites is essential for elucidating complex biological processes. However, conventional methods for AcCoA detection often suffer from limitations, including cumbersome procedures, substantial matrix interference, dependence on advanced instrumentation, and inadequate sensitivity for trace-level analysis in biological matrices. To address these challenges, this study developed a fluorescent switch biosensor for AcCoA detection based on iron ion (Fe 3+ )-mediated fluorescence modulation. The sensor utilizes nitrogen-doped carbon dots (N-CDs) synthesized through pyrolysis of sodium alginate and melatonin. The resulting amorphous N-CDs (average diameter: 3.75 nm) exhibit strong blue fluorescence. The biosensor demonstrates high sensitivity and selectivity, achieving a linear detection range of 1–200 μM with a LOD of 0.268 μM. Moreover, owing to the low cytotoxicity and rapid response of the N-CDs, the system enabled real-time monitoring of AcCoA in live microalgal cells, showing a linear fluorescence response in Ochromonas sp. cultures across volumes ranging from 0.8 to 10 mL. This work provides a robust and biocompatible platform with significant potential for advancing AcCoA-related biological research.