A. Plot of membrane absorbance from 350–700 nm. The ECM-derived membranes exhibits superior optical transparency compared to traditional transparent cell culture inserts such as Transwell polyester membranes. B. Digital photograph of COL-MAT membrane demonstrating its optical clarity. This membrane was trimmed to the approximate size used for device bonding and held over printed text using forceps. C. Plot of relative membrane permeability representing measurements of 20kDa FITC-dextran transport across COL, COL-MAT, COL-ALG, and PE membrane inserts over a period of 6 hours under continuous parallel flow perfusion at a flow rate of 100 µl/hr. ** and ns represent P < 0.01 and not significant, respectively. D. SEM visualization of collagen type I-alginate (COL-ALG) membrane surface ultrastructure demonstrating larger pores and fenestrations (arrows) created by using alginate as a water-soluble sacrificial material, scale bar = 2 µm. E. Atomic force microscopy (AFM) nanoindentation measurement of the elastic modulus for hydrated COL, 80:20 COL-MAT, 50:50 COL-MAT, 20:80 COL-MAT, and Transwell PE membranes. * represents P < 0.05.