Three-dimensional pattering of poly (ethylene Glycol) hydrogels through surface-initiated photopolymerization.

Photopolymerizable hydrogels have been investigated extensively for biomedical applications, specifically in the area of tissue engineering. While fabrication approaches have shown promise in designing hydrogel scaffolds that guide cell function, the ability to spatially control localization in three-dimensions has been limited. We have developed a method for generating two-dimensional and three-dimensional (3D) patterns within multilayered poly(ethylene glycol) diacrylate (PEG-DA) hydrogels. Covalently attached hydrogel layers are formed using precursor solutions with a 10:1 mole ratio of PEG-DA to PEG-aminoacrylate (Acr-PEG-NH2). Upon illumination of the precursor with visible light (wavelength = 514 nm), a hydrogel layer forms with pendant amine groups induced by the presence of Acr-PEG-NH2 macromer. Pendant amine groups are further functionalized with free carboxyl groups present on the visible light photoinitiator eosin, allowing for the formation of subsequent hydrogel layers. Using noncontact photolithography, the prepolymer solution is polymerized through a photomask, resulting in hydrogel structures with distinct pattern formation in each layer. Unreacted regions immobilized with eosin can be subsequently filled with a different PEG hydrogel. The technique presented shows a great potential for tissue engineering applications, for biosensors, and in the formation of cell and protein patterning for biotechnology.