Rhodamine 123 Transport Assay

Functionality of the multi drug resistance-1 (MDR-1) transporter was performed according standard protocol using a commercially available Rhodamine 123 assay (Sigma Aldrich) (Sampaziotis et al., 2017). Rhodamine 123 transport was determined by incubating the cultures with Rhodamine 123 (100 μM, Sigma Aldrich) for 5°min at 37°C. Subsequently, specificity of the MDR-1 transporter was determined by blocking the transporter with Verapamil (10°μM, Sigma Aldrich) for 30°min at 37°C prior to Rhodamine 123 incubation (100°μM, Sigma Aldrich). Confocal analysis was performed to determine MDR-1 activity. Images were acquired with a Leica SP5 confocal microscope (LEICA) equipped with a 488-nm laser.