Volume 103, Issue 9, Pages 2033-2042 (November 2012) A Three-Dimensional In Vitro Tumor Platform for Modeling Therapeutic Irreversible Electroporation  Christopher B. Arena, Christopher S. Szot, Paulo A. Garcia, Marissa Nichole Rylander, Rafael V. Davalos  Biophysical Journal  Volume 103, Issue 9, Pages 2033-2042 (November 2012) DOI: 10.1016/j.bpj.2012.09.017 Copyright © 2012 Biophysical Society Terms and Conditions

Figure 1 (a) Experimental setup for IRE pulse delivery in collagen I hydrogel-based in vitro tumors in which PDAC cells are embedded. (b) Geometry and mesh used in the finite element model for simulating the electrical and thermal response of the in vitro tumors to IRE. Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 2 A live/dead assay for assessment of cell death after IRE pulse delivery of 30 V (a), 150 V (b), 300 V (c), and 450 V (d). Live cells were stained green using Calcein AM and dead cells were stained red using propidium iodide. Images were tiled to reconstruct the entire surface of the IRE-treated in vitro tumors. The bright rings encircling the hydrogels are a consequence of out-of-plane fluorescence at the rounded edges. Scale bars, 2.5 mm. Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 3 (a) A sharp interface between live (green; left) and dead (red; right) cells at the threshold boundary for cell death with submillimeter resolution. (b) 3D reconstruction at this interface highlights the transition zone between live and dead cells and demonstrates that IRE-induced cell death was uniform throughout the in vitro tumors. The dotted lines in (a) define the representative region from which the image in (b) was taken. Scale bars, 400 μm (a) and 200 μm (b). Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 4 (a) An H&E stain for further assessment of cell viability after IRE pulse delivery of 450 V through in vitro tumors seeded with 50 × 106 cells/ml. (b and c) Cells located within the IRE-treated regions appeared to be devoid of most cytoplasmic material (b), whereas cells located within the untreated regions appeared normal, with intact cell membranes (c). (d and e) Dotted lines in (a) define the transition zone at the live/dead cell interface. An F-actin stain (red) was used to determine the effect of IRE-pulse delivery on the cytoskeleton of PPT-8182 cells cultured within the IRE-treated (d) and untreated (e) regions of the in vitro tumors. The actin cytoskeleton within the IRE-treated cells appears permanently disrupted. Nuclei were stained with DAPI (blue). Scale bars, 250 μm (a), 50 μm (b and c), and 25 μm (d and e). Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 5 Change in current (a) and temperature (b) delivered through the in vitro tumors during IRE performed at 150 V, 300 V, 450 V, and 600 V. The treatment consisted of 80 100-μs-long pulses delivered at a rate of 1/s. The bars with 1 standard deviation indicate the experimentally measured values. The data points along the line illustrate the results of the numerical model, which was optimized to match the measured changes in current and temperature from onset to offset of pulsing. Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 6 Surface plots from the numerical model showing the electric-field distribution (a), temperature distribution (b), and conductivity distribution (c) at the end of an 80-s IRE treatment at 300 V. The upper and lower triangles along the scale bars indicate maximum and minimum values, respectively, present within the entire domain. In the case of (c) these values are consistent with those reported in Table 1 for the electrode and plate domains. Regions experiencing values outside the given color range (e.g., electrode and plate conductivity) assume the color associated with the limits of the displayed data. Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 7 Overlay of electric-field contours predicted by the numerical model at the end of 80-s IRE treatments at 300 V (a) and 450 V (b) with the corresponding live/dead tiled images from Fig. 2. The field contours shown are at 400 V/cm (inner), 500 V/cm (middle), and 600 V/cm (outer). The contour labeled 500 V/cm denotes the threshold for cell death. Scale bars, 2.5 mm. Biophysical Journal 2012 103, 2033-2042DOI: (10.1016/j.bpj.2012.09.017) Copyright © 2012 Biophysical Society Terms and Conditions