Mlct c

The elasticity of a single cell treated with AEA was measured using a commercial atomic force microscope (XE120 model, Park Systems, Suwon, Korea) and an optical microscope to control the position of the gold-coated silicon nitride cantilevers (MLCT-C, Bruker Corporation, Billerica, Massachusetts, USA) with a nominal spring constant of 0.01 N/m. Cells were seeded at the density of 3 × 10⁴ cells/well on glass coverslips and next treated with 1 µM AEA or 0.07% v/v DMSO (CTR) for 24 h. All measurements were performed at RT in a medium without FBS.
Force curves were collected randomly from chosen cells from the region around the cell center. The force was set up to 4 nN, the approach velocity to 9 µm/s and a grid of 4 × 4 points on each cell was selected. The elastic modulus (E) values were calculated based on the subtraction of the two force curves: the calibration curve recorded on the glass coverslip without the cells and the other curves collected on a given cell [41 (link)]. The obtained force-versus-indentation-curve was analyzed by means of the Sneddon extension of the Hertz model assuming that the tip is an infinitely stiff indenter modeled by a parabola [42 (link)]. The results were presented for the indentation depth of 300 nm.

To obtain a topographical cell image, the AFM tip was placed on the cell surface and then using scanning mode was moved horizontally along the cell surface while applying a constant force (500 – 800 pN) to the cell surface. Scanned images were 100 μm × 100 μm at the digital density of 512 pixels × 512 pixels. A stylus-type AFM probe (model MLCT-C, k = 15 pN nm^-1, Bruker, Santa Barbara, CA, United States) was used to perform the cell surface scanning at 0.15 Hz frequency at room temperature. Height and deflection images were collected with Bioscope software and analyzed using Nanoscope software.

Mechanical properties of BD PuraMatrix Peptide Hydrogel (Corning, Tewskbury, MA, USA) were investigated using atomic force microscopy (AFM, CellHesion head, JPK Instruments, Berlin, Germany) in force mapping mode. To probe hydrogel samples, commercially-available silicon nitride cantilevers (MLCT-C, Bruker, Billerica, MA, USA) with a nominal spring constant of 0.01 N/m were applied. Force curves, i.e., dependencies between cantilever deflection and relative sample position, were acquired over a grid of 8 × 8 pixels within a scan area of 50 × 50 μm. The maximum load force (F) was 5 nN and load speed of 8 μm/s was maintained. Young’s modulus was determined using Hertz contact mechanics as described previously [77 (link)]. Briefly, the following relation between the load force (F) and resulting indentation (Δz) for the paraboloidal assumption of the probing tip was applied: $F=\frac{4·\sqrt{R}·E}{3·\left(1-v^2\right)}·\Delta z^{\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$
JPK Data Processing software was used to apply this equation to the experimental data to obtain the value of Young’s modulus for each force curves. The final Young’s modulus was obtained by averaging all force curves and was expressed as a mean and standard deviation.