Figure 1: Digital projection photolithography for fabricating micropatterned 3D tissue culture matrices with bound proteins for axon growth and guidance studies. (A) Black-and-white images corresponding to desired geometries (left) are uploaded via computer to a digital light projection device, which reflects UV light pixel-for-pixel through an objective lens onto a curable hydrogel (center). A series of digital "masks" can be used for curing the gels onto regular cell culture substrates (upper right), and for irradiating gels for binding proteins. Lower-right image represents two different fluorescent proteins covalently bound to the 3D gel in specific locations. (B) Fluorescent images show protein binding location as well as axon growth (red) from dorsal root ganglion neurons (green). A control protein led to equal axon growth in upper and lower forks, while NT-3 increased, and Sema-3A decreased, the amount of axon growth in the region of the bound protein, marked with arrows. All scale bars: 500 μm. Adapted from Moore and Curley, 2011; and Horn-Ranney et al., 2013, 2014. DLP: Digital projection lithography; NT-3: neurotrophin-3; Sema-3A: semaphorin 3A; UV: ultraviolet.