Utilizing inherent fluorescence of therapeutics to analyze real-time uptake and multi-parametric effector kinetics.

The precise detection of pharmaceutical drug uptake and knowledge of a drug's efficacy at the single-cell level is crucial for understanding a compound's performance. Many pharmaceutical drugs, like the model substances Doxorubicin, Mitoxantrone or Irinotecan, have a distinctive natural fluorescence that can be readily exploited for research purposes. Utilizing this respective natural fluorescence, we propose a method analyzing simultaneously in real-time the efficiency, effects and the associated kinetics of compound-uptake and efflux in mammalian cells by flow cytometry. We show that real-time flow cytometric quantification of compound-uptake is reliably measured and that analyzing their respective uptake kinetic provides additional valuable information which can be used for improving drug dosage and delivery. Exploiting the native fluorescence of natural compounds is clearly advantageous compared to the usage of non-related fluorescent uptake-reporter substances, possibly yielding in unphysiological data. Flow cytometric analysis allows live-dye based multi-parametric high-throughput screening of pharmaceutical compound activity, improving cytotoxicity testing by combining several assays into a single, high resolution readout. This approach can be a useful tool identifying potential inhibitors for multiple drug resistance (MDR), representing a major challenge to the targeted treatment of various diseases.