posted on 2015-12-16, 21:06authored byRodney
T. Chen, Silvia Marchesan, Richard A. Evans, Katie E. Styan, Georgina K. Such, Almar Postma, Keith
M. McLean, Benjamin W. Muir, Frank Caruso
The photolithographical patterning of hydrogels based
solely on
the surface immobilization and cross-linking of alkyne-functionalized
poly(ethylene glycol) (PEG-tetraalkyne) is described. Photogenerated
radicals as well as UV absorption by a copper chelating ligand result
in the photochemical redox reduction of Cu(II) to Cu(I). This catalyzes
the alkyne–azide click reaction to graft the hydrogels onto
an azide-functionalized plasma polymer (N3PP) film. The
photogenerated radicals were also able to abstract hydrogen atoms
from PEG-tetraalkyne to form poly(α-alkoxy) radicals. These
radicals can initiate cross-linking by addition to the alkynes and
intermolecular recombination to form the PEG hydrogels. Spatially
controlling the two photoinitiated reactions by UV exposure through
a photomask leads to surface patterned hydrogels, with thicknesses
that were tunable from tens to several hundreds of nanometers. The
patterned PEG hydrogels (ca. 60 μm wide lines) were capable
of resisting the attachment of L929 mouse fibroblast cells, resulting
in surfaces with spatially controlled cell attachment. The patterned
hydrogel surface also demonstrated spatially resolved chemical functionality,
as postsynthetic modification of the hydrogels was successfully carried
out with azide-functionalized fluorescent dyes via subsequent alkyne–azide
click reactions.