Biomedical Engineering Reference
In-Depth Information
These data show that nano-BLMs are a powerful membrane
system that overcomes the disadvantage of poor long-term stability
of classical BLMs. However, classical BLMs have also been de-
veloped further in recent years in order to diminish their draw-
backs such as long-term stability and applicability in chip based
assays. Glass supports with a single pore of 100-400 nm in diame-
ter served as supports for BLMs, which are stable for up to two
weeks.
30
In another approach, giant unilamellar vesicles are sucked
on a single hole by means of low pressure, which ruptures the ves-
icle and generates a bilayer within seconds.
31
Nevertheless, these
systems still only provide a bilayer covering one single hole,
whereas nano-BLMs are composed of more than 10
9
individual
bilayers.
2.
Pore-Suspending Membranes on CPEO3
(
i
)
Impedance Analysis of Pore-Suspending Membranes on
Porous Alumina with Fully Opened Pore Bottoms
Nano-BLMs proved to be a robust system for the investigation
of ion channels on a single channel level (see Section III). Due to
the method of preparation, nano-BLMs still contain some organic
solvent, which is reflected in the mentioned fluctuations in mem-
brane resistance and the obtained lateral diffusion coefficients.
28
Several membrane proteins lose activity in the presence of organic
solvents such as
n
-decane and hence bilayers prepared without ad-
dition of solvent are highly desirable. For BLMs this has been real-
ized by the method of Montal and Mueller, who established sol-
vent-free lipid bilayers by the membrane folding method.
32
Already some years ago, we followed a strategy to form pore-
suspending bilayers starting from large unilamellar vesicles
(LUVs).
22,33,34
With this method, it is not only possible to gain sol-
vent-free pore-spanning membranes, but in addition it holds the
potential for establishing lipid bilayers with high protein density.
As a starting point, porous substrates were functionalized with a
thiol-component to chemically distinguish between the upper sur-
face and the inner pore walls, which should prevent the fusion of
vesicles within the pores. Yet, these membranes proved to be ra-
ther leaky, as shown by EIS.
34
To achieve highly insulating pore-
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