Red emissive N, Cl-doped carbon dots for detection of tea polyphenols and lysosomal imaging at the cellular level

Tea polyphenols (TP), which is accounting for 15-30% of the dry weight of green tea and are widely used in the food industry as antioxidants, preservatives, color preservatives, and flavoring agents. To determine the con-centration of TP, a fluorescent method based on nitrogen and chlorine co-doped carbon dots (R-CDs) was investigated. The R-CDs we prepared showed red emission with an absolute quantum yield (QY) of approximately 16.67 +/- 0.85%. The limit of detection (LOD) was calculated to be approximately 68 +/- 0.94 ng/mL, with an R2 of 0.999 over the TP range of 1-20 mu g/mL. Compared to the ferrous tartrate standard curve method, the concentration of TP in green tea, which was purchased from the market, detected using our method showed an error within 5%, indicating good potential applications in the food industry. Cell imaging experiments suggested that the R-CDs exhibit excellent lysosomal targeting as the Pearson's correlation coefficient (PCC) in colocalization analysis was found to be 0.91. Further experiments showed that owing to their excitation-independent emission and high QY, the R-CDs could be applied to not only for detecting TP content but also for targeting lysosomes as substitute for commercial dyes.

Automated summary

A fluorescent method based on nitrogen and chlorine co-doped carbon dots was developed for determining the concentration of tea polyphenols (TP). The method showed good accuracy and potential applications in the food industry. Additionally, the carbon dots exhibited excellent lysosomal targeting and could be used as substitutes for commercial dyes.