Live Cell Volume and Mass Quantification

Volume and mass were analyzed with live imaging as previously described^{76 (link)}. Briefly, cells were trypsinized, counted, and resuspended in medium supplemented with 1 mg/ml Alexa Fluor 488 Dextran (MW 10 kD; Life Technologies) at a concentration of 10⁶ cells/ml before being injected in PDMS chips coated with fibronectin with a known height of 23 µm. Finally, the chamber was immersed in medium to prevent evaporation. Acquisitions were performed on a Ti inverted (Nikon) or an Axio Observer microscope (Carl Zeiss) at 37 °C, with 5% CO2 atmosphere, using a ×20 dry objective (NA 0.5 phase), or a SFluor 20× objective (NA 0.75 without phase ring) for the mass measurements. Images were acquired using MetaMorph (Molecular Devices). Images were acquired with a CoolSNAP HQ2 camera (Photometrics) for fluorescence or a PHA SICS camera (PHA SICS) for mass measurements. Images were analyzed with a custom-made MatLab program (MathWorks).