Enzyme-assisted photolithography for spatial functionalization of hydrogels.

The ability to form functional polymeric patterning structures has important implications for the studies of cell biology, tissue engineering, and medical diagnostics. We have developed a novel enzyme-assisted photolithography (EAPL) method for spatial functionalization of hydrogels via a high throughput fashion. A bisacrylated peptide crosslinker, containing a protease cleavable amino acid sequence and caged by a photolabile moiety, is used during hydrogel polymerization. A facile two-step process is employed, including UV exposure to decage the peptide crosslinker at a desired area and protease development to specifically digest gels at UV treated regions only. Importantly, proteolysis of the peptide bonds generates free nucleophilic amine groups at the patterned area that can be further functionalized. Using this strategy and caspase-3 as the enzyme developer, we demonstrate the simultaneous generation of topographical and functional patterns into poly(ethylene glycol) (PEG) hydrogels. We show that 20 microm-wide line arrays functionalized with arginine-glycine-aspartic acid (RGD)-containing peptides can be used to generate cell patterns with individual cell resolution. We also fabricated arrays 20 mum diameter cavities decorated with B lymphocyte specific anti-CD19, which was used to achieve a 600-fold enrichment of B-cells from a 0.1% starting B-cell mixture. The simple fabrication process, straightforward chemistry and an all-aqueous based biocompatible and environmentally friendly approach render EAPL a versatile platform to construct biologically responsive 2D patterns or 3D scaffolds for lab-on-a-chip systems and tissue engineering.