Rhodamine b

PS is a validated material for cell-culture applications and offers substantial advantages over PDMS for use with microfluidic systems for in vitro drug testing (Toepke and Beebe, 2006 (link); Sasaki et al., 2010 (link); Van Midwoud et al., 2012 (link); Lohasz et al., 2019 (link); Ravaynia et al., 2020 (link)). To confirm that PS did not feature substantial molecule absorption, 50 μL of 100 μM rhodamine-B (83689, Sigma-Aldrich, Buchs, Switzerland) solution were loaded into the microwells and incubated for 24 hours (Lohasz et al., 2019 (link)). Fluorescence images of the microwells were captured before the loading of the dye, at 1 and 24 h after sample loading, and after wash-out of the dye by means of an inverted microscope (Nikon Ti-E, Nikon, Egg, Switzerland), as shown in Figure S10A. The single chip was incubated at 37°C and 5% CO₂. After 1 day of dye incubation, 50 μL of supernatant solution of each microwell unit were collected and compared to 50 μL of rhodamine B reference solutions (1.5, 3.3, 6.2, 12.5, 25, 50, and 100 μM), which were incubated in a 96-well microplate (675090, Greiner Bio-One GmbH, St. Gallen, Switzerland). The relative fluorescence intensity of all samples was measured using a microplate reader (Infinite M200 Pro, TECAN, Männedorf, Switzerland) at 550 nm excitation - 580 nm emission (Figure S10B). All conditions were analyzed in quadruplicates.