title: Fabrication of poly(ethylene glycol) hydrogel microstructures using photolithography.
abstract: The fabrication of hydrogel microstructures based upon poly(ethylene glycol) diacrylates, dimethacrylates, and tetraacrylates patterned photolithographically on silicon or glass substrates is described. A silicon/silicon dioxide surface was treated with 3-(trichlorosilyl)propyl methacrylate to form a self-assembled monolayer (SAM) with pendant acrylate groups. The SAM presence on the surface was verified using ellipsometry and time-of-flight secondary ion mass spectrometry. A solution containing an acrylated or methacrylated poly(ethylene glycol) derivative and a photoinitiator (2,2-dimethoxy-2-phenylacetophenone) was spin-coated onto the treated substrate, exposed to 365 nm ultraviolet light through a photomask, and developed with either toluene, water, or supercritical CO2. As a result of this process, three-dimensional, cross-linked PEG hydrogel microstructures were immobilized on the surface. Diameters of cylindrical array members were varied from 600 to 7 micrometers by the use of different photomasks, while height varied from 3 to 12 micrometers, depending on the molecular weight of the PEG macromer. In the case of 7 micrometers diameter elements, as many as 400 elements were reproducibly generated in a 1 mm2 square pattern. The resultant hydrogel patterns were hydrated for as long as 3 weeks without delamination from the substrate. In addition, micropatterning of different molecular weights of PEG was demonstrated. Arrays of hydrogel disks containing an immobilized protein conjugated to a pH sensitive fluorophore were also prepared. The pH sensitivity of the gel-immobilized dye was similar to that in an aqueous buffer, and no leaching of the dye-labeled protein from the hydrogel microstructure was observed over a 1 week period. Changes in fluorescence were also observed for immobilized fluorophore labeled acetylcholine esterase upon the addition of acetyl acholine.
authors.affiliation: Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122, USA.
authors.forename: A
authors.initials: A
authors.lastname: Revzin
authors.forename: R J
authors.initials: RJ
authors.lastname: Russell
authors.forename: V K
authors.initials: VK
authors.lastname: Yadavalli
authors.forename: W G
authors.initials: WG
authors.lastname: Koh
authors.forename: C
authors.initials: C
authors.lastname: Deister
authors.forename: D D
authors.initials: DD
authors.lastname: Hile
authors.forename: M B
authors.initials: MB
authors.lastname: Mellott
authors.forename: M V
authors.initials: MV
authors.lastname: Pishko
mesh_terms: D000110:Acetylcholinesterase / Q000737:chemistry; D001672:Biocompatible Materials; D015374:Biosensing Techniques / Q000379:methods*; D002245:Carbon Dioxide; D005898:Glass; D020100:Hydrogels / Q000737:chemistry*; D008422:Materials Testing; D008856:Microscopy, Fluorescence; D008863:Microspheres; D008970:Molecular Weight; D011092:Polyethylene Glycols / Q000737:chemistry*; D012825:Silicon; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D013501:Surface-Active Agents; D002245:Carbon Dioxide; D011092:Polyethylene Glycols; D000110:Acetylcholinesterase; D012825:Silicon