Rapid and Sensitive Fluorometric Quantification of Black Carbon in Biological Fluids

The increase in wildfire frequency worldwide has contributed to persistent atmospheric black carbon (BC) pollution, which was closely relative to multiple adverse health effects. Accurate quantification of BC in biological tissues and fluids is fundamental for evaluating its health effect; however, existing analytical methodologies are hindered by time-consuming protocols, low throughput, and the need for expensive instrumental infrastructure. In this study, we developed a fluorometric method for quantifying BC in various biological fluids with the advantages of simplicity, high sensitivity, and low cost. Specifically, this technique enables quantification of five distinct types of BC across diverse biological liquids with a detection limit (LOD) of 0.23-7.57 mg/L. The method's LOD is comparable to the established advanced techniques for BC quantification (e.g., femtosecond illumination technique and laser desorption/ionization mass spectrometry) but avoids the use of expensive instruments. Compared with conventional ultraviolet-visible (UV-Vis) spectrophotometry, the fluorometric technique demonstrates higher accuracy and less interference from proteins, water-soluble ions, or suspended particles. The practicability of the method was examined through the A549 cell-based toxicological assays. The biologically effective exposure dose (BED, a parameter for evaluating the actual exposure dose of chemicals) of BC to A549 cells was determined to be approximately 30 pg/cell, which overcame a fundamental measurement challenge regarding the BED of BC in cellular assays. Overall, the present method addresses a significant challenge in BC analysis, thus facilitating its accurate risk assessment.