The spatial resolution of silicon photoelectrochemistry is improved to 500 nm by using amorphous silicon, 60 times improvement as compared to crystalline silicon.
Spatial
control of surface functionalization and interactions is essential
for microarray-based analysis. This study reports the fabrication
of two-dimensional molecular films with site-specific functionalities,
forming microarrays at discrete locations. Arrays of microsized gold
disks were produced on a silicate membrane using microfabrication.
On these arrays, orthogonal self-assembly of molecules was performed
that can specifically bind to gold or silicate. The gold array elements
were functionalized with a range of alkanethiols and the silicate
with polymeric poly-l-lysine-grafted-poly(ethylene glycol)
(PLL-PEG). The surface functionalization on the gold disk array and
the surrounding substrate was characterized at each step using X-ray
photoelectron spectroscopy (XPS) to show that alkanethiols are specifically
attached to the gold. PLL-PEG was used to provide resistance against
nonspecific protein and cell adsorption and attached exclusively to
the silicate. The effectiveness of the surface chemistry was validated
by the selective self-assembly of a gold nanoparticle monolayer array
on the gold regions. In a more sophisticated example, selective adhesion
of MCF-7 cells to anti-EpCAM antibody modified gold areas of the gold–silicate
surface was demonstrated to give a cell microarray. This study provides
a general approach to fabricate chemical patterns on silicon-based
devices with the convergence of microfabrication and material-specific
surface modification, which may be useful to expand the functionalities
and potential applications for patterned biomolecular films. Importantly,
the ability to pattern surfaces with different surface chemistries
is not limited to planar surfaces using this orthogonal surface-coupling
approach.
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