Stat0.2laud

To measure the tissue’s elastic modulus, we removed the hECT from its bioreactor, and glued it down with Kwik-cast sealant (World Precision Instruments) to the bottom of a petri dish, applying the sealant to polar ends of the hECT, after 1 minute the dish was filled with media for subsequent measurements under AFM. The AFM measurements were performed with Flex-Bio AFM (Nanosurf AG, Switzerland) equipped with an inverted microscope Axio Observer (Carl Zeiss) and an environmental control enclosure. The AFM was operated in static force mode. The cantilever had a spring constant of 0.27N/m and silicon tip radius < 10nm (Stat0.2LAuD, Nanosurf AG, Switzerland). We measured force spectroscopy at 13 different spots (N=8 for each spot) with distances from the edge of the tissue ranging from 200 to 300 μm as shown in Figure 5a. The force curves, as shown in Figure 5b, were analyzed and the elastic modulus was obtained by applying the Hertz model [33 (link), 34 (link)] to the forward approach curves using the ANA control and analysis software (Nanosurf AG, Switzerland) resulting in an average elastic modulus of approximately 10.7 +/− 3.7 kPa for the hECT. This value was later used in the finite element (FEM) model using COMSOL Multiphysics (ver. 5.4, COMSOL, Inc., MA, USA).

1 × 10^5 cells MDA-MB-231 cells were plated on rimmed petri dishes (Ted Pella, Inc) coated with 1 mg/mL unlabeled gelatin. The Young’s modulus of MDA-MB-231 cells in L15 phenol red free cell culture media (Gibco) with 10% FBS (Gemini Bio) was measured using a Flex-Bio AFM (Nanosurf AG, Switzerland) equipped with an 178 inverted microscope Axio Observer (Carl Zeiss) and an environmental control enclosure. The AFM is operated in static force mode, and with a cantilever with spring constant 0.22 N, and its silicon tip with radius <10 nm (Stat0.2LAuD, Nanosurf AG, Switzerland). Force curves were measured across cells within 30 μm windows with each data point collected every 2 μm. A custom Matlab (MathWorks, Natick, MA, USA) code was written to select and average the elasticity of 25 data points that have the highest contact points with the cell, which corresponds to the nucleus of the cell. The Sneddon model was used to approximate the Young’s modulus, with a cone with half angle 15°, fitting from 0 – 500 pN.