Thermo k calibration

Tapping mode AFM using the Bruker BioScope Catalyst Atomic Force coupled with Zeiss LSM5 Confocal Fluorescence Microscope was used on the cells at 37°C in cell culture media. AFM deflection images of cells were used in the imaging experiment. In the force measurement, sharp silicon nitride AFM probes (tip radius, 20 nm) were employed (Bruker Corp., USA). The spring constants of AFM tips were calibrated to be 0.10–0.11 N m⁻¹ and deflection sensitivities were 45–50 nm V⁻¹, using Thermo K Calibration (Agilent Technologies, USA). The approaching/retracting speed of the AFM tip during the force curve measurement was 6 μm s⁻¹. Force–distance curves were recorded to obtain cell elasticity (Young’s modulus, E) of individual cells. For each time point, at least 20 single cells, 20 cells at the base of the iFA and 20 cells at the tip of the scar were measured with over 15 force–distance curves per cell to obtain significant results. The Young’s modulus was calculated via the Scanning Probe Image Processor (SPIP) software (Image Metrology, Denmark) by converting the force–distance curves to force–separation curves and fitting the Sneddon variation of the Hertz model, which describes conical tips indenting elastic samples.