The individual slices were collated, using ImageJ software,22 to create a three-dimensional rendering of the myotube. From the three-dimensional rendering, the length, average width, and average thickness of each myotube were determined. The Stoney’s equation approach was used to calculate the compressive stress generated by the myotube from the voltage output of the photo-detector (Volts). The equations and methods described previously3 were modified to account for the measured width of the myotube instead of assuming the myotube filled the entire width of the cantilever. Equations 1, 2 are restated versions for cantilever tip deflection (δ) and stress produced by the myotube, assuming a uniform thick film the full

Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical width of the cantilever (σc). The system parameters used in these equations are the system-specific coefficient relating voltage to laser position on the photo-detector (Cdetector), the angle of the laser and detector relative to the plane of the cantilever (θ), the path length of the laser from the cantilever tip to the detector (P), the elastic modulus of silicon (ESi), the thicknesses of the cantilever (tSi) and myotube

(tf), Poisson’s ratio of Inhibitors,research,lifescience,medical silicon (vSi), cantilever length (L), and the widths of the cantilever (wSi) and myotube (wmyotube) δ=2L3tan[θ2−12arctan(tanθ−VoltageCdetector×P×cosθ)]. (1) In Eq. 2, the myotube is approximated as a uniform film. Therefore, the force in the myotube is equal to the force in the film, leading to Eq. 3 by equating the calculation of force from stress and CSA. To determine stress in the myotube Inhibitors,research,lifescience,medical (σmyotube), Eq. 3 can be rearranged to form Eq. 4 σc= ESitSi36tf(1−vSi)(tf+tSi)3δ2L2×11+tftSi, (2) Fmyotube=σc×tf×wSi=σmyotube×tf×wmyotube, (3) σmyotube=σc ×(wSi /wmyotube). (4) For the FEA approach, the cantilever geometry was drawn and meshed in NX 8.5 (Siemens PLM Software, Plano, TX) as a set of square elastic elements, with a fixed boundary condition at one end to produce a cantilevered geometry. For each myotube experimentally tested, Inhibitors,research,lifescience,medical the myotube was modeled

as an ellipsoid on top of the cantilever in NX using the measured dimensions and positions acquired from confocal microscopy. In the FEA model, the myotube and cantilever beam were meshed with 3D square elements. The coincident nodes were merged, which allowed for the simulation of a fully adhered myotube to the cantilever beam. The stress in the myotube was determined using the FEA model by selleck kinase inhibitor altering the force most so that the deflection matched the value for deflection calculated from Eq. 1. The force in each myotube calculated from the Stoney’s method was compared to the force calculated from the FEA for that myotube. Multiple linear regression was applied to the force calculated from the Stoney’s and FEA approaches to fit values to the physical dimensions of the myotubes and the interactions of these variables using a best fit approach to selecting predictive variables.