Biomedical Engineering Reference
In-Depth Information
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Figure 10.10
Silane gradient preparation through UV irradiation of n-octadimethyl-
chlorosilane (A). Ozone treatment for increasing time periods across
the gradient lead to a gradual increase the concentration of carbonyl
functional groups (B).
Modified from Gallant et al.
173
Elwing et al.
86
and Bhat et al.
176
Allen et al.
26
also observed an increase in Fn
adsorption on hydrophobic surfaces. However, in a study by Wei et al.
9
Fn
was found to bind to the hydrophilic end of the gradient, with contact angles
ranging from 31 to 401. This discrepancy highlights that, unlike popular
belief in the past, the contact angle alone is not believed to be the sole
contributor for the attachment of proteins and that surface chemistry itself
also plays an important role. Other techniques for preparing chemical gra-
dients with silanes include microcontact printing and oxidation of a uniform
silane coating through UV irradiation through a gradient mask.
.
NOTE: The term 'click chemistry' was originally coined by Kolb et al.
174
to
describe a specific range of chemical processes that quickly and reliably join
small units together.
Semi-fluorinated SAMs have been shown to prevent the attachment of
some biomolecules.
177
Using surface plasmon resonance (SPR), the immo-
bilisation of immunoglobulin was monitored, with adsorption only observed
on non-SAM coated regions. N-Octadecyltrichlorosilane (OTS) is commonly
used in chemical modifications of a surface. It can be easily deposited and
has been shown to be effective in preventing cell attachment due to its
hydrophobic nature.
178
Upon UV exposure, the hydrocarbon chain degrades,
leaving a terminal OH region. The hydroxyl-terminated regions can then be
further functionalised. Through the use of a gradient mask or shutter sys-
tem, a density gradient could be prepared. Matsuzawa et al.
178
deposited
OTS onto glass and silicon surfaces. The surface was exposed to UV light
through a mask, patterning the surface. N-(2-Aminoethyl-3-aminopropyl)-
trimethoxysilane (EDA) was then selectively immobilised onto the surface
followed by seeding with SK-N-SH neuroblastoma cells. It was found that the
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