Fabrication of Combinatorial ECM Microarray

The ECM microarray was fabricated from single-component ECMs or multi-component mixtures of the following ECM proteins: collagen IV (C, mouse, Southern Biotech; Cat. No. 1250–04S), fibronectin (F, bovine, Sigma; Cat No. F1141), laminin (L, mouse, Life Technologies; Cat No. 23017–015), gelatin (G, bovine, Sigma; Cat No. G1393), heparan sulfate (H, mouse, Sigma; Cat No. H4777), and Matrigel (M, mouse, BD Biosciences; Cat No. 356231) (Fig. 1A). The single factor ECMs were further mixed at equal mass ratios (ie, 1:1, 1:1:1, etc.) to obtain a total of 63 unique ECM combinations, each with 6 replicates on each ECM microarray slide. The final concentration of all ECM combinations was held constant at 0.5 mg/ml. The ECMs were deposited using an OmniGrid Accent Microarrayer (Gene Machines) onto a surface-reactive glass slides (Schott H, Nexterion) for covalent protein conjugation, as described previously^{18 (link)}. The resulting combinatorial ECM microarray consisted of individual microenvironments in the form of circular “islands” that were 0.3 mm in diameter and 0.3 mm apart from neighboring islands. After covalent attachment of the ECMs, the microarray slides were air dried and transferred into vacuum sealed boxes and stored in the dark at 4 °C.