Figure 4.

Sequential biochemical patterning in tetrazine click gels. To demonstrate the potential for biochemical patterning, 7.5 wt % tetrazine click hydrogels were formed with 1 mM norb-GGKGGC, leaving pendant thiols in the network. Aqueous solutions of norbornene/fluorophore labeled bovine serum albumin (norb/FL-BSA and norb/TAMRA-BSA, 0.1 mg/mL) and the photoinitiator 2-hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methyl-1- propanone (I2959, 2.2 mM) were sequentially swollen into the network and patterned through a photomask using collimated UV light (365 nm, 10 mW/cm², 10 min) to create a grid pattern (100 μm lines, 100 μm spacing). High patterning fidelity was observed, as measured line widths were 101 ± 1 μm (note: epifluorescent images of the pattern at the gel surface; scalebars =200 μm; n = 12 for line width measurements).