This paper presents a strategy for immobilizing biomolecules on a
photoactivable surface. A self-assembled monolayer is prepared by adsorbing an ω-functionalized
dialkyl disulfide on gold. Functional
groups of this monolayer are converted in two steps into a benzophenone
derivative with an overall yield
of 50 ± 10%. Several independent techniques (ellipsometry,
X-ray photoelectron spectroscopy, scanning
electron microscopy, atomic force microscopy, radiolabel assay, and
autoradiography) characterize the
reaction and photoimmobilization of antibodies on this surface.
The photoimmobilized antibodies cover
the surface as a homogeneous and dense monolayer that could not be
disrupted by vigorous washing with
the detergent Tween 20. Immunoassays demonstrated specific
recognition of the immobilized immunoglobulins as measured by their complexation with alkaline
phosphatase-linked antibodies. The method
of photoimmobilization used here leads to a homogeneous single layer of
IgGs, in which the proteins
maximize their contact with the surface. Residual adsorption of
IgG on the nonirradiated surface of
benzophenone remains one limitation of this approach.
Progressively higher coverages of IgGs on the
surface did not lead to strictly proportional changes of the biological
activity of these surfaces, probably
because of interactions between the IgGs in the film. This method
of photoimmobilization is nonetheless
useful as an experimental system to immobilize other proteins because
it is simple, flexible, and efficient.
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